Edit

Configuration

Configuration for scalafmt is defined in a plain text file .scalafmt.conf using HOCON syntax.

Here is an example .scalafmt.conf:

align.preset = more    // For pretty alignment.
maxColumn = 100 // For my wide 30" display.

Most popular

maxColumn

Default: maxColumn = 80

• Keep in mind that 80 characters fit perfectly on a split laptop screen with regular resolution.
• GitHub mobile view only shows 80 characters and sometimes you might review code on your phone.
• Consider refactoring your code before of choosing a value above 100.

assumeStandardLibraryStripMargin

This parameter simply says the .stripMargin method was not redefined by the user to assign special meaning to indentation preceding the | character. Hence, that indentation can be modified.

# Defaults
assumeStandardLibraryStripMargin = false
align.stripMargin = true

If true, lines starting with the margin character | (or another if specified in the .stripMargin(...) call) will be indented differently.

If align.stripMargin is true, they will align with the opening triple-quote """ in interpolated and raw string literals. Otherwise, they will be indented relative to the start of the opening line.

val example1 =
  s"""Examples:
     |  * one
     |  * two
     |  * $three
     |""".stripMargin

val example1 =
  s"""Examples:
  |  * one
  |  * two
  |  * $three
  |""".stripMargin

Config for this example:

assumeStandardLibraryStripMargin = true
align.stripMargin = true

val example1 =
  s"""|Examples:
    |  * one
    |  * two
    |  * $three
    |""".stripMargin

val example1 =
  s"""|Examples:
      |  * one
      |  * two
      |  * $three
      |""".stripMargin

Config for this example:

assumeStandardLibraryStripMargin = true
align.stripMargin = false

The pipe character can immediately follow the opening """

val example2 =
  s"""|Examples:
      |  * one
      |  * two
      |  * $three
      |""".stripMargin

val example2 =
  s"""|Examples:
  |  * one
  |  * two
  |  * $three
  |""".stripMargin

Config for this example:

assumeStandardLibraryStripMargin = true
align.stripMargin = true

Scala Dialects

The formatter supports various dialects defined and supported by scalameta parser. However, for any given file, one and only one dialect is supported, and runner.dialect must be used to select it.

Default: runner.dialect = "default"

Available dialects are:

• scala211
• scala212
• scala212source3
• scala213
• scala213source3
• scala3
• sbt0137
• sbt1

You can also specify runner.dialect for a subset of files using fileOverride:

fileOverride {
  "glob:**/scala3-subproject/src/main/scala/**" {
    runner.dialect = scala3
  }
}

Scala 3

Since v3.0.0, scalafmt supports Scala 3 features that can be enabled by changing the dialect of the scalameta parser.

runner.dialect = scala3
---
open class MyOpenClass()
val myQuote = '{ expr }
val mySplice = ${ expr }
enum class Weekday {
  case Monday, Tuesday, Wednesday, Thursday, Friday
}

Please also see rewrite rules for Scala 3.

Scala 2 with -Xsource:3

Also since v3.0.0, if using -Xsource:3 option for Scala 2 compiler, you can change the dialect to Scala213Source3, which will allow to format some of the new syntax backported from Scala 3.

Presets

Some sections provide preset values to set multiple parameters at once. These are always accessed via the preset key of the appropriate section, including top-level.

Top-level presets

• preset=default: this preset is implicit and sets all values to their defaults.
• preset=IntelliJ: this preset is defined as

    preset = default
    indent.defnSite = 2
    optIn.configStyleArguments = false

• preset=defaultWithAlign: this preset is defined as

    preset = default
    align.preset = more

• preset=Scala.js: this preset is defined as

    preset = default
    binPack.preset = true
    align.openParenCtrlSite = false
    indent.callSite = 4
    docstrings.style = Asterisk
    importSelectors = binPack
    newlines {
      neverInResultType = true
      neverBeforeJsNative = true
      sometimesBeforeColonInMethodReturnType = false
    }
    runner.optimizer {
      forceConfigStyleOnOffset = 500
      forceConfigStyleMinArgCount = 5
    }

Appending to preset collections

If, instead of redefining the default or preset value of a list or a map parameter, you'd like to append to it, use the following syntax:

// set
a.b.c.list = [ ... ]
a.b.c.dict = { ... }

// append; "+" must be the only key
a.b.c.list."+" = [ ... ]
a.b.c.dict."+" = { ... }

Indentation

indent.main

Since v3.0.0.

This parameter controls the primary code indentation. Various context-specific overrides are defined below, within this section.

Default: indent.main = 2

indent.significant

Since v3.0.0.

This parameter controls the amount of significant indentation used when optional braces rules apply.

By default, equals to indent.main.

object a {
  if (foo)
    bar
  else
    baz

  if foo then
     bar
     bar
  else
     baz
     baz
}

object a {
  if (foo)
    bar
  else
    baz

  if foo then
    bar
    bar
  else
    baz
    baz
}

Config for this example:

runner.dialect = scala3
indent.main = 2
indent.significant = 3

indent.callSite

Default: indent.callSite = 2

Example:

function(
  argument1, // indented by 2
  ""
)

function(
argument1, // indented by 2
""
)

Config for this example:

indent.callSite = 2

indent.ctrlSite

This parameter controls indentation within control expressions (if/while/etc). If not set, the value of indent.callSite applies.

Since v3.0.0.

if (
    foo && // indented by 4
    bar
) {
  baz
}

if (
 foo && // indented by 4
 bar
) {
  baz
}

Config for this example:

indent.callSite = 2
indent.ctrlSite = 4

if (
  foo && // indented by 2
  bar
) {
  baz
}

if (
 foo && // indented by 2
 bar
) {
  baz
}

Config for this example:

indent.callSite = 2

indent.defnSite

Default: indent.defnSite = 4

Same as indent.callSite except for definition site. Example:

def function(
    parameter1: Type1 // indented by 4
): ReturnType

def function(
parameter1: Type1 // indented by 4
): ReturnType

Config for this example:

indent.defnSite = 4

indent.ctorSite

Since v2.5.0.

Applies to constructors. Defaults to indent.defnSite.

class A(
    field1: Type1 // indented by 4
) {
  def function2(
    parameter1: Type1 // indented by 2
  ): ReturnType = None
}

class A(
 field1: Type1 // indented by 4
) {
 def function2(
  parameter1: Type1 // indented by 2
 ): ReturnType = None
}

Config for this example:

indent.ctorSite = 4
indent.defnSite = 2

indent.caseSite

Since v3.0.0.

Applies indentation to case values before arrow.

Default: indent.caseSite = 4

x match {
  case _: Aaaaaa |
       _: Bbbbbb |
       _: Cccccc =>
}

x match {
  case _: Aaaaaa |
      _: Bbbbbb |
      _: Cccccc =>
}

Config for this example:

maxColumn = 20
indent.caseSite = 5

indent.extendSite

Default: indent.extendSite = 4

This parameter defines indentation used for the extends A with B or derives A, B sequences in a template (class, trait, object, enum, etc.).

trait Foo
    extends A {
  def foo: Boolean =
    true
}

trait Foo extends A {
  def foo: Boolean = true
}

Config for this example:

indent.extendSite = 4
maxColumn = 20

indent.withSiteRelativeToExtends

Since v2.5.0.

This parameter defines additional indentation used for the with elements of an extends A with B sequence in a template.

Default: indent.withSiteRelativeToExtends = 0

trait Foo
    extends A
      with B
      with C
      with D
      with E {
  def foo: Boolean = true
}

trait Foo extends A with B with C with D with E {
  def foo: Boolean = true
}

Config for this example:

indent.extendSite = 4
indent.withSiteRelativeToExtends = 2
maxColumn = 30

indent.commaSiteRelativeToExtends

Since v3.0.0

This parameter defines additional indentation used for the post-comma elements of an extends A, B or derives A, B sequences of a template.

Added to support Scala 3, which allows to specify multiple parents with a comma.

Default: indent.commaSiteRelativeToExtends = 2

trait Foo
    extends A,
        B,
        C,
        D,
        E {
  def foo: Boolean =
    true
}

trait Foo extends A, B, C, D, E {
  def foo: Boolean = true
}

Config for this example:

runner.dialect = scala3
indent.extendSite = 4
indent.commaSiteRelativeToExtends = 4
maxColumn = 20

indent.extraBeforeOpenParenDefnSite

Since v3.0.0

This parameter applies to definitions and sets extra indentation (relative to the indentation of the body) used for parameter groups when

• the definition has a body (that needs differentiating from)
• newlines.beforeOpenParenDefnSite is set

Default: indent.extraBeforeOpenParenDefnSite = 0

case class fooClass
  (foo1: String)
  (
      foo2: String,
      foo3: String
  )(foo5: String)
abstract class fooClass
  (foo1: String)
  (
      foo2: String,
      foo3: String
  )(foo5: String) {
  def fooDef
    (foo1: String)
    (
        foo2: String,
        foo3: String
    )(foo5: String)
}
def fooDef(foo1: String)
  (
      foo2: String,
      foo3: String
  )(foo5: String) = {
  // body
}

case class fooClass
  (foo1: String)
  (foo2: String, foo3: String)
  (foo5: String)
abstract class fooClass
  (foo1: String)
  (foo2: String, foo3: String)
  (foo5: String) {
  def fooDef
    (foo1: String)
    (foo2: String, foo3: String)
    (foo5: String)
}
def fooDef
  (foo1: String)
  (foo2: String, foo3: String)
  (foo5: String) = {
  // body
}

Config for this example:

maxColumn = 25
newlines.beforeOpenParenDefnSite = fold

case class fooClass
  (foo1: String)
  (
      foo2: String,
      foo3: String
  )(foo5: String)
abstract class fooClass
    (foo1: String)
    (
        foo2: String,
        foo3: String
    )(foo5: String) {
  def fooDef
    (foo1: String)
    (
        foo2: String,
        foo3: String
    )(foo5: String)
}
def fooDef(foo1: String)
    (
        foo2: String,
        foo3: String
    )(foo5: String) = {
  // body
}

case class fooClass
  (foo1: String)
  (foo2: String, foo3: String)
  (foo5: String)
abstract class fooClass
  (foo1: String)
  (foo2: String, foo3: String)
  (foo5: String) {
  def fooDef
    (foo1: String)
    (foo2: String, foo3: String)
    (foo5: String)
}
def fooDef
  (foo1: String)
  (foo2: String, foo3: String)
  (foo5: String) = {
  // body
}

Config for this example:

maxColumn = 25
indent.extraBeforeOpenParenDefnSite = 2
newlines.beforeOpenParenDefnSite = fold

case class fooClass
  (foo1: String)
  (
      foo2: String,
      foo3: String
  )(foo5: String)
abstract class fooClass
 (foo1: String)
 (
     foo2: String,
     foo3: String
 )(foo5: String) {
  def fooDef
    (foo1: String)
    (
        foo2: String,
        foo3: String
    )(foo5: String)
}
def fooDef(foo1: String)
 (
     foo2: String,
     foo3: String
 )(foo5: String) = {
  // body
}

case class fooClass
  (foo1: String)
  (foo2: String, foo3: String)
  (foo5: String)
abstract class fooClass
  (foo1: String)
  (foo2: String, foo3: String)
  (foo5: String) {
  def fooDef
    (foo1: String)
    (foo2: String, foo3: String)
    (foo5: String)
}
def fooDef
  (foo1: String)
  (foo2: String, foo3: String)
  (foo5: String) = {
  // body
}

Config for this example:

maxColumn = 25
indent.extraBeforeOpenParenDefnSite = -1
newlines.beforeOpenParenDefnSite = fold

indentOperator

Normally, the first eligible break inside a chain of infix operators is indented by 2.

This group of parameters allows overriding which infix operators are eligible and controls when indentation is omitted.

indentOperator.topLevelOnly

If true, only top-level infix operators are eligible to be exempted from the default indentation rule.

Default: indentOperator.topLevelOnly = true

function(
  a &&
    b
)
function {
  a &&
  b
}

function(
  a &&
    b
)
function {
  a &&
    b
}

Config for this example:

indentOperator.topLevelOnly = true

function(
  a &&
  b
)
function {
  a &&
  b
}

function(
  a &&
    b
)
function {
  a &&
    b
}

Config for this example:

indentOperator.topLevelOnly = false

indentOperator.exclude

Defines a regular expression for excluded infix operators. If an eligible operator matches, it will not be indented.

Default: indentOperator.exclude = "^(&&|\\|\\|)$"

indentOperator.include

Defines a regular expression for included infix operators. If an eligible operator matches and is not excluded explicitly by indentOperator.exclude, it be will indented.

Default: indentOperator.include = ".*"

indentOperator.preset

• default
  • use defaults for all fields
• spray (also akka)
  • set include = "^.*=$", exclude = "^$"

Alignment

Alignment describes formatting which inserts additional spaces to align certain tokens on different lines vertically.

Apart from a few special cases, the way alignment works is as follows:

• for each line, alignment stops are identified, by looking up each token in align.tokens (matching token, owner and, if specified, the owner's parent)
• for two candidate lines, respective alignment stops are compared (first stop on one line to the first one on the other, etc); the only exception are the single-line comments which are compared regardless of their stop position
• two tokens will match if:
  • both tokens have the same token category; a token's category is the value associated with its type in align.tokenCategory mapping or, if missing, its type
  • both owners have the same tree category; similarly, a tree's category is the value for its type in align.treeCategory mapping or the type itself
  • both owners belong to the same "statement container"; this is determined internally and usually selects the nearest containing block, template, match, argument or parameter group.
• if two tokens match:
  • if there's a space before them, they themselves will be aligned on the right
  • if there's a space after them, the next tokens will be aligned on the left

Align has several nested fields, which you can customize. However, it comes with four possible presets: none, some, more, & most.

align.preset

Default: some

align.preset=none

x match { // false for case arrows
  case 2 => 22 // also comments!
  case 22 => 222 // don't align me!
}

x match { // false for case arrows
  case 2  => 22 // also comments!
  case 22 => 222 // don't align me!
}

Config for this example:

align.preset = none

Pro tip: Enable this setting to minimize git diffs/conflicts from renamings and other refactorings, without having to ignore whitespace changes in diffs or use --ignore-all-space to avoid conflicts when git merging or rebasing.

Starting with the introduction of align.stripMargin parameter in v2.5.0, one must explicitly enable it to get earlier behaviour of align.preset=none. See assumeStandardLibraryStripMargin.

align.preset=some

x match { // true for case arrows
  case 2  => 22
  case 22 => 222
}

val x = 2 // false for assignment
val xx = 22

case object B
    extends A // false for `extends`
case object BB extends A

x match { // true for case arrows
  case 2 => 22
  case 22 => 222
}

val x = 2 // false for assignment
val xx = 22

case object B extends A // false for `extends`
case object BB extends A

Config for this example:

align.preset = some

align.preset=more

val x  = 2 // true for assignment
val xx = 22

case object B
    extends A // true for `extends`
case object BB extends A

q -> 22 // true for various infix operators
qq -> 3 // and also comments!

for {
  x <- List(
    1
  ) // true for alignment enumerator
  yyy <- List(2)
} yield x ** yyy

x match { // true for multiple tokens across multiple lines
  case 1  => 1  -> 2  // first
  case 11 => 11 -> 22 // second

  // A blank line separates alignment blocks.
  case `ignoreMe` => 111 -> 222
}

// Align assignments of similar type.
def name   = column[String]("name")
def status = column[Int]("status")
val x      = 1
val xx     = 22

// Align sbt module IDs.
libraryDependencies ++= Seq(
  "org.scala-lang" % "scala-compiler" % scalaVersion.value,
  "com.lihaoyi" %% "sourcecode" % "0.1.1"
)

val x = 2 // true for assignment
val xx = 22

case object B extends A // true for `extends`
case object BB extends A

q -> 22 // true for various infix operators
qq -> 3   // and also comments!

for {
  x <- List(1) // true for alignment enumerator
  yyy <- List(2)
} yield x ** yyy

x match { // true for multiple tokens across multiple lines
  case 1 => 1 -> 2 // first
  case 11 => 11 -> 22 // second

  // A blank line separates alignment blocks.
  case `ignoreMe` => 111 -> 222
}

// Align assignments of similar type.
def name = column[String]("name")
def status = column[Int]("status")
val x = 1
val xx = 22

// Align sbt module IDs.
libraryDependencies ++= Seq(
  "org.scala-lang" % "scala-compiler" % scalaVersion.value,
  "com.lihaoyi" %% "sourcecode" % "0.1.1"
)

Config for this example:

align.preset = more

align.preset=most

for {
  // align <- with =
  x   <- List()
  yyy  = 2
  // aligns body by arrow
  zzz <- new Integer {
           def value = 3
         }
} yield x

for {
  // align <- with =
  x <- List()
  yyy = 2
  // aligns body by arrow
  zzz <- new Integer {
    def value = 3
  }
} yield x

Config for this example:

align.preset = most

Note. Only for the truest vertical aligners. Feel free to open PR enabling more crazy vertical alignment here. Expect changes.

align.tokens

Default: [caseArrow]

An align token contains a code (the string literal of an operator of token) and a list of owners; each owner entry in turn contains an optional regex (the kind of the closest tree node that owns that token), and a list of parents (to match the tree containing the owner of the token).

To find the owner part for a custom tree, look for its type prefix using ScalaFiddle Playgroud or AST Explorer.

x match {
  case 1  => 1 -> 2
  case 11 => 11 -> 22
}

x match {
  case 1 => 1 -> 2
  case 11 => 11 -> 22
}

Config for this example:

align.tokens = [{
  code = "=>"
  owners = [{
    regex = "Case"
  }]
}]

val x = List(
  "org.scala-lang" %% "scala-compiler" % scalaVersion.value,
  "com.lihaoyi" %% "sourcecode" % "0.1.1"
)

val x = List(
"org.scala-lang" %% "scala-compiler" % scalaVersion.value,
"com.lihaoyi" %% "sourcecode" % "0.1.1"
)

Config for this example:

align.tokens = [
  {
    code = "%"
    owners = [{
      regex = "Term.ApplyInfix"
    }]
  }, {
    code = "%%"
    owners = [{
      regex = "Term.ApplyInfix"
    }]
  }
]

case class Foo(
    firstParam:  Int,
    secondParam: String,
    thirdParam:  Boolean
) {
  def Foo(
      firstParam: Int,
      secondParam: String,
      thirdParam: Boolean
  ) = ???
}

case class Foo(
  firstParam: Int,
  secondParam: String,
  thirdParam: Boolean
) {
  def Foo(
    firstParam: Int,
    secondParam: String,
    thirdParam: Boolean
  ) = ???
}

Config for this example:

align.tokens."+" = [{
  code = ":"
  owners = [{
    regex = "Term\\.Param"
    parents = [ "Ctor\\.Primary" ]
  }]
}]

case class Foo(
    firstParam: Int,
    secondParam: String,
    thirdParam: Boolean
) {
  def Foo(
      firstParam:  Int,
      secondParam: String,
      thirdParam:  Boolean
  ) = ???
}

case class Foo(
  firstParam: Int,
  secondParam: String,
  thirdParam: Boolean
) {
  def Foo(
    firstParam: Int,
    secondParam: String,
    thirdParam: Boolean
  ) = ???
}

Config for this example:

align.tokens."+" = [{
  code = ":"
  owners = [{
    parents = [ "Defn\\." ]
  }]
}]

align.arrowEnumeratorGenerator

Default: align.arrowEnumeratorGenerator = false

for {
  x <- new Integer {
    def value = 2
  }
} yield x

for {
  x <- new Integer {
     def value = 2
     }
} yield x

Config for this example:

align.arrowEnumeratorGenerator = false

for {
  x <- new Integer {
         def value = 2
       }
} yield x

for {
  x <- new Integer {
     def value = 2
     }
} yield x

Config for this example:

align.arrowEnumeratorGenerator = true

align.closeParenSite

This parameter controls whether to align the closing parentheses when we aligned the opening one (see openParenXxxSite parameters below) and the respective danglingParentheses.xxxSite is set.

Since v3.0.0.

Default: align.closeParenSite = false

function(arg1, // align by (
         arg2,
         arg3
        )

function(arg1, // align by (
    arg2,
 arg3)

Config for this example:

align.closeParenSite = true
align.openParenCallSite = true
danglingParentheses.callSite = true

function(arg1, // align by (
         arg2,
         arg3
)

function(arg1, // align by (
    arg2,
 arg3)

Config for this example:

align.closeParenSite = false
align.openParenCallSite = true
danglingParentheses.callSite = true

align.openParenCallSite

Default: align.openParenCallSite = false

Default changed from true to false in v1.6.

foo(arg1, arg2)

function(arg1, // align by (
         arg2,
         arg3
)

function(argument1, argument2)

foo(arg1, arg2)

function(arg1, // align by (
    arg2,
 arg3)

function(
  argument1,
  argument2)

Config for this example:

align.openParenCallSite = true

foo(arg1, arg2)

function(
  arg1, // no align by (
  arg2,
  arg3
)

function(argument1, argument2)

foo(arg1, arg2)

function(arg1, // no align by (
    arg2,
 arg3)

function(
  argument1,
  argument2)

Config for this example:

align.openParenCallSite = false

align.openBracketCallSite

Since v3.0.4.

If set explicitly, will be used for the left bracket in type arguments, instead of align.openParenCallSite.

align.openParenCtrlSite

This parameter controls alignment after ( in if/while/for.

Default: align.openParenCtrlSite = false

align.openParenDefnSite

Default: align.openParenDefnSite = false

Default changed from true to false in v1.6.

class IntString(int: Int,
                string: String
)

class IntStringLong(int: Int,
                    string: String,
                    long: Long
)

class IntString(int: Int, string: String)

class IntStringLong(int: Int,
    string: String,
  long: Long)

Config for this example:

align.openParenDefnSite = true

class IntString(
    int: Int,
    string: String
)

class IntStringLong(
    int: Int,
    string: String,
    long: Long
)

class IntString(int: Int, string: String)

class IntStringLong(
      int: Int,
    string: String,
  long: Long
)

Config for this example:

align.openParenDefnSite = false

align.openBracketDefnSite

Since v3.0.4.

If set explicitly, will be used for the left bracket in type parameters, instead of align.openParenDefnSite.

align.openParenTupleSite

This parameter controls aligning of tuples to their opening parenthesis. If not specified, will use the value of align.openParenCallSite.

Since v3.0.0.

object a {
  foo(
    bar,
    baz
  )
  (bar,
   baz
  )
}

object a {
  foo(bar, baz)
  (bar, baz)
}

Config for this example:

maxColumn = 10
align.openParenCallSite = false
align.openParenTupleSite = true

object a {
  foo(bar,
      baz
  )
  (bar,
   baz
  )
}

object a {
  foo(bar, baz)
  (bar, baz)
}

Config for this example:

maxColumn = 10
align.openParenCallSite = true

align.stripMargin

See assumeStandardLibraryStripMargin.

Default: align.stripMargin = true

This functionality is enabled in all presets except align.preset=none where it was disabled since the parameter's introduction in v2.5.0.

align.multiline

If this flag is set, when alignment is applied, multiline statements will not be excluded from search of tokens to align.

Since v2.5.0.

Default: align.multiline = false

for {
  a      <- aaa
  bbb    <- bb
  cccccc <- c {
    3
  }
  dd     <- ddddd
} yield ()

for {
  a <- aaa
  bbb <- bb
  cccccc <- c {
    3
  }
  dd <- ddddd
} yield ()

Config for this example:

align.preset = more
align.multiline = true

for {
  a   <- aaa
  bbb <- bb
  cccccc <- c {
    3
  }
  dd <- ddddd
} yield ()

for {
  a <- aaa
  bbb <- bb
  cccccc <- c {
    3
  }
  dd <- ddddd
} yield ()

Config for this example:

align.preset = more
align.multiline = false

align.allowOverflow

If this flag is set, as long as unaligned lines did not overflow, we will not check whether alignment causes any lines to overflow the maxColumn setting.

Since v3.0.0.

Default: align.allowOverflow = false

It's also enabled by default in align.preset = most.

Newlines

The newlines.* options are used to configure when and where scalafmt should insert newlines.

You might be interested in the Vertical Multiline section.

newlines.source

Since v2.5.0.

This parameter controls the general approach to line breaks, and whether to take into account existing newlines in the source. The default value (if the parameter is not specified) is the classic, original way. Below are the alternatives.

These alternatives are EXPERIMENTAL and might change in the future without regard to any edition settings, until fully released (and this message deleted).

newlines.source=keep

This approach attempts to preserve line breaks in the input whenever possible.

newlines.source=fold,unfold

These two approaches completely ignore existing line breaks, except around comments and blank lines (i.e., multiple consecutive newlines).

Might require increasing runner limits (runner.optimizer.maxVisitsPerToken, possibly even runner.maxStateVisits), to avoid SearchStateExploded exceptions.

fold attempts to remove line breaks whenever possible resulting in a more horizontal, or vertically compact look.

unfold, on the other hand, is intended for those who prefer a more vertical, or horizontally compact look.

Both settings attempt to play nice with other parameters, but some combinations are prohibited and will result in an error.

newlines.topLevelStatementBlankLines

Since v3.0.0.

This parameter controls when to add blank lines before and/or after a top-level statement (a member of a package or template; nesting is allowed but not within a block). Special cases:

• the rules do not apply to non-indented packages (but do consider other statements within those packages)
• end markers are handled through a setting for the statement they mark
• imports and exports are processed as a group of consecutive statements
• also see Newlines around package or template body

This parameter might reduce the number of blank lines but will not eliminate them completely unless corresponding value is negative.

Each entry on this list consists of the following fields:

• regex
  • a regular expression to match the type of the statement
  • if unspecified, will match all valid statements
  • see align.tokens for instructions on how to find the type
• maxNest
  • basically, limits indentation level (not actual indentation) of a statement
  • unindented statements (under source-level unindented package) have nest level of 0, those under them are 1 etc.
  • if unspecified, will match any nesting level
• minBreaks (default: 1)
  • sets the minimum number of line breaks between the first and last line of a statement (i.e., one less than the number of lines the statement spans).
  • for instance, minBreaks=0 will apply to all statements, whereas 1 will require at least one line break (that is, a multi-line statement).
• blanks
  • if omitted while the entry matches, serves to exclude another entry
  • before: number of lines to be added before a matching statement; if negative (v3.0.1), lines will be removed unless before a comment
  • after: number of lines to be added after a matching statement
    • for instance, if a package matches, this controls how many lines need to be added after all statements of a package, not after the first line which declares the package name
    • same logic as above applies to negative values
  • beforeEndMarker:
    • end markers themselves will not be matched against any rule; blanks before them will come from beforeEndMarker and blanks after from after
  • beforeAll and afterAll (v3.0.1): if set explicitly, replaces the respective before or after value before the first or after the last statement of a template or indented package; otherwise, the before or after value will be capped at 1
  • can be specified as a single integer, to set just before and after to the same value:

// these two are equivalent
newlines.topLevelStatementBlankLines = [
  { blanks { before = 1, after = 1, beforeEndMarker = 0 } }
]
newlines.topLevelStatementBlankLines = [
  { blanks = 1 }
]

If you'd like to override or exclude some cases, add them explicitly:

newlines.topLevelStatementBlankLines = [
  { maxNest = 0, blanks = 2 } // uses 2 blanks for all unindented statements
  { regex = "^Import" } // excludes import groups; blanks are not specified
]

If multiple entries match a statement, an entry with the lowest minBreaks will be selected. Since we'll be adding lines, this will increase the span of the statement and might potentially lead to another entry, with a higher minBreaks, to match as well, which is undesirable.

Default: newlines.topLevelStatementBlankLines = []

import org.scalafmt
package core { // no newline added here
  class C1 {}
  object O { // nor here
    val x1 = 1
    val x2 = 2
    def A = "A"
    def B = "B"
  } // nor here
  class C2 {}
}

import org.scalafmt
package core { // no newline added here
  class C1 {}
  object O { // nor here
    val x1 = 1
    val x2 = 2
    def A = "A"
    def B = "B"
  } // nor here
  class C2 {}
}

Config for this example:

newlines.topLevelStatementBlankLines = []

import org.scalafmt

package core {
  class C1 {}

  object O {
    val x1 = 1
    val x2 = 2
    def A = "A"
    def B = "B"
  }
  class C2 {}
}

import org.scalafmt
package core {
  class C1 {}
  object O {
    val x1 = 1
    val x2 = 2
    def A = "A"
    def B = "B"
  }
  class C2 {}
}

Config for this example:

newlines.topLevelStatementBlankLines = [
  {
    blanks { before = 1 }
  }
]

import org.scalafmt
package core {
  class C1 {}
  object O {
    val x1 = 1
    val x2 = 2
    def A = "A"
    def B = "B"
  }

  class C2 {}
}

import org.scalafmt
package core {
  class C1 {}
  object O {
    val x1 = 1
    val x2 = 2
    def A = "A"
    def B = "B"
  }
  class C2 {}
}

Config for this example:

newlines.topLevelStatementBlankLines = [
  {
    blanks { after = 1 }
  }
]

import org.scalafmt

package core {
  class C1 {}

  object O {
    val x1 = 1
    val x2 = 2
    def A = "A"
    def B = "B"
  }

  class C2 {}
}

import org.scalafmt
package core {
  class C1 {}
  object O {
    val x1 = 1
    val x2 = 2
    def A = "A"
    def B = "B"
  }
  class C2 {}
}

Config for this example:

newlines.topLevelStatementBlankLines = [
  {
    blanks = 1
  }
]

package core {

  object O {

    val x1 = 1

    val x2 = 2

    def A =
      "A"

    def B = {
      "B"
    }

  }

}

package core {
  object O {
    val x1 = 1
    val x2 = 2
    def A =
      "A"
    def B = {
      "B"
    }
  }
}

Config for this example:

newlines.topLevelStatementBlankLines = [
  {
    minBreaks = 0
    blanks = 1
  }
]

import org.scalafmt

package core {

  object O {
    val x1 = 1
    val x2 = 2
    def A =
      "A"

    def B = {
      "B"
    }

  }

}

import org.scalafmt
package core {
  object O {
    val x1 = 1
    val x2 = 2
    def A =
      "A"
    def B = {
      "B"
    }
  }
}

Config for this example:

newlines.topLevelStatementBlankLines = [
  {
    minBreaks = 2
    blanks = 1
  }
]

newlines.topLevelStatements

Deprecated in v3.0.0.

This parameter and its companion newlines.topLevelStatementsMinBreaks have been deprecated and will be removed in a subsequent release.

An equivalent setting is

newlines.topLevelStatementBlankLines = [
  {
    regex = "^Pkg|^Defn\\.|^Decl\\."
    blanks = 1
    minBreaks = <value of topLevelStatementsMinBreaks>
  }
]

If newlines.topLevelStatementBlankLines is set, this setting will be ignored.

Newlines around package or template body

Since v3.0.0.

This group of parameters controls whether to enforce a blank line before the first or after the last statement of a package or template (i.e., body of a class, object, trait, enum).

These parameters will not cause any blank lines to be removed.

newlines.topLevelBodyIfMinStatements

topLevelBodyIfMinStatements can be before and/or after, while topLevelBodyMinStatements limits when the rule is applied.

# Defaults
newlines.topLevelBodyIfMinStatements = []
newlines.topLevelBodyMinStatements = 2

import org.scalafmt
package core {
  class C1 {
    def one = 1
  }
  object O1 {
    val one = 1
    def two = 2
  }
  class C2 {}
}

import org.scalafmt
package core {
  class C1 {
    def one = 1
  }
  object O1 {
    val one = 1
    def two = 2
  }
  class C2 {}
}

Config for this example:

newlines.topLevelBodyIfMinStatements = []

import org.scalafmt
package core {

  class C1 {
    def one = 1
  }
  object O1 {

    val one = 1
    def two = 2
  }
  class C2 {}
}

import org.scalafmt
package core {
  class C1 {
    def one = 1
  }
  object O1 {
    val one = 1
    def two = 2
  }
  class C2 {}
}

Config for this example:

newlines.topLevelBodyIfMinStatements = [before]

package core {
  class C1 {
    def one = 1
  }
  object O1 {
    val one = 1
    def two = 2

  }
  class C2 {}

}

package core {
  class C1 {
    def one = 1
  }
  object O1 {
    val one = 1
    def two = 2
  }
  class C2 {}
}

Config for this example:

newlines.topLevelBodyIfMinStatements = [after]

import org.scalafmt
package core {

  class C1 {
    def one = 1
  }
  object O1 {

    val one = 1
    def two = 2

  }
  class C2 {}

}

import org.scalafmt
package core {
  class C1 {
    def one = 1
  }
  object O1 {
    val one = 1
    def two = 2
  }
  class C2 {}
}

Config for this example:

newlines.topLevelBodyIfMinStatements = [before,after]

newlines.beforeTemplateBodyIfBreakInParentCtors

This parameter will force a blank line before the first statement of a template body if the token before extends and the { (or, in scala3, :) token are not on the same line.

Default: newlines.beforeTemplateBodyIfBreakInParentCtors = false

package core {
  class C1 extends S { // no breaks between "C1" and "{"
    def one = 1
  }
  class C1(
      param: Int
  ) extends S { // no breaks between ")" and "{"
    def one = 1
  }
  class C1 extends S { // no breaks between "C1" and "=>"
    self =>
    def one = 1
  }
  class C1
      extends S { // break between "C1" and "{"

    def one = 1
  }
}

package core {
  class C1 extends S { // no breaks between "C1" and "{"
    def one = 1
  }
  class C1(
    param: Int
  ) extends S { // no breaks between ")" and "{"
    def one = 1
  }
  class C1 extends S { // no breaks between "C1" and "=>"
    self =>
    def one = 1
  }
  class C1
    extends S { // break between "C1" and "{"
    def one = 1
  }
}

Config for this example:

newlines.source = keep
newlines.beforeTemplateBodyIfBreakInParentCtors = true

package core {
  class C1 extends S { // no breaks between "C1" and "{"
    def one = 1
  }
  class C1(
      param: Int
  ) extends S { // no breaks between ")" and "{"
    def one = 1
  }
  class C1 extends S { // no breaks between "C1" and "=>"
    self =>
    def one = 1
  }
  class C1
      extends S { // break between "C1" and "{"
    def one = 1
  }
}

package core {
  class C1 extends S { // no breaks between "C1" and "{"
    def one = 1
  }
  class C1(
    param: Int
  ) extends S { // no breaks between ")" and "{"
    def one = 1
  }
  class C1 extends S { // no breaks between "C1" and "=>"
    self =>
    def one = 1
  }
  class C1
    extends S { // break between "C1" and "{"
    def one = 1
  }
}

Config for this example:

newlines.source = keep
newlines.beforeTemplateBodyIfBreakInParentCtors = false

newlines.beforeMultiline

Since v2.7.0

This parameter controls whether to force a new line before a multi-line body of case/if/def/val and how to format it if the space is allowed. (For additional control with assignment expressions, please also see newlines.forceBeforeMultilineAssign below.)

It accepts the same values as newlines.source (and defaults to that parameter's setting).

NB: for breaks before parameters of a multi-line lambda, use multiline with newlines.beforeCurlyLambdaParams.

a match {
  // had space after "=>"
  case a =>
    if (step != 0)
      d.name should be("dir" + step)
  // had newline after "=>"
  case a =>
    if (step != 0)
      d.name should be("dir" + step)
}

a match {
  // had space after "=>"
  case a => if (step != 0)
      d.name should be("dir" + step)
  // had newline after "=>"
  case a =>
    if (step != 0)
      d.name should be("dir" + step)
}

Config for this example:

newlines.beforeMultiline = unfold

a match {
  // had space after "=>"
  case a => if (step != 0)
      d.name should be("dir" + step)
  // had newline after "=>"
  case a => if (step != 0)
      d.name should be("dir" + step)
}

a match {
  // had space after "=>"
  case a => if (step != 0)
      d.name should be("dir" + step)
  // had newline after "=>"
  case a =>
    if (step != 0)
      d.name should be("dir" + step)
}

Config for this example:

newlines.beforeMultiline = fold

a match {
  // had space after "=>"
  case a => if (step != 0)
      d.name should be("dir" + step)
  // had newline after "=>"
  case a =>
    if (step != 0)
      d.name should be("dir" + step)
}

a match {
  // had space after "=>"
  case a => if (step != 0)
      d.name should be("dir" + step)
  // had newline after "=>"
  case a =>
    if (step != 0)
      d.name should be("dir" + step)
}

Config for this example:

newlines.beforeMultiline = keep

a match {
  // had space after "=>"
  case a =>
    if (step != 0)
      d.name should be("dir" + step)
  // had newline after "=>"
  case a =>
    if (step != 0)
      d.name should be("dir" + step)
}

a match {
  // had space after "=>"
  case a => if (step != 0)
      d.name should be("dir" + step)
  // had newline after "=>"
  case a =>
    if (step != 0)
      d.name should be("dir" + step)
}

Config for this example:

# newlines.beforeMultiline = classic

newlines.forceBeforeMultilineAssign

Since v3.0.0

This section controls whether to force a break before a multi-line body of an assignment expression unless it can be formatted on a single line (or is enclosed in braces). By default, the rule is disabled. It takes precedence over newlines.beforeMultiline settings.

It can take the following values:

• never: the rule is disabled
• any: applies to any assignment expression (def, assignment to a var, default value of a method parameter, etc.)
• def: applies only to definitions which can potentially be parameterized (def, macro, given alias, etc.)
• anyMember: applies to members of a class/trait/object
• topMember: applies to members of a class/trait/object which itself can only be nested within a sequence of class/trait/object definitions

It replaces deprecated newlines parameters beforeMultilineDef=unfold and alwaysBeforeMultilineDef=true which, if this parameter is not set, map to def.

class A {
  // break, allows params (even if it doesn't define any)
  def foo =
    func(
      foo,
      bar
    )
  // no break, doesn't allow params
  val foo = func(
    foo,
    bar
  )
  def foo = {
    def a =
      func(
        foo,
        bar
      )
    val a = func(
      foo,
      bar
    )
  }
}

class A {
  // break, allows params (even if it doesn't define any)
  def foo = func(foo, bar)
  // no break, doesn't allow params
  val foo = func(foo, bar)
  def foo = {
    def a = func(foo, bar)
    val a = func(foo, bar)
  }
}

Config for this example:

maxColumn = 17
newlines.forceBeforeMultilineAssign = def

class A {
  class B {
    // break, a top member
    def foo = func(
      foo,
      bar
    )
    // break, a top member
    val foo = func(
      foo,
      bar
    )
  }
  def foo = {
    // no break, not a member
    def a = func(
      foo,
      bar
    )
    // no break, not a member
    val a = func(
      foo,
      bar
    )
    new A with B {
      // no break, not a top member
      def foo =
        func(
          foo,
          bar
        )
      // no break, not a top member
      val foo =
        func(
          foo,
          bar
        )
    }
  }
}

class A {
  class B {
    // break, a top member
    def foo = func(foo, bar)
    // break, a top member
    val foo = func(foo, bar)
  }
  def foo = {
    // no break, not a member
    def a = func(foo, bar)
    // no break, not a member
    val a = func(foo, bar)
    new A with B {
      // no break, not a top member
      def foo = func(foo, bar)
      // no break, not a top member
      val foo = func(foo, bar)
    }
  }
}

Config for this example:

maxColumn = 19
newlines.forceBeforeMultilineAssign = topMember

// all disabled, no breaks
class A {
  def foo = func(
    foo,
    bar
  )
  val foo = func(
    foo,
    bar
  )
  def foo = {
    def a = func(
      foo,
      bar
    )
    val a = func(
      foo,
      bar
    )
  }
}

// all disabled, no breaks
class A {
  def foo = func(foo, bar)
  val foo = func(foo, bar)
  def foo = {
    def a = func(foo, bar)
    val a = func(foo, bar)
  }
}

Config for this example:

maxColumn = 17
newlines.forceBeforeMultilineAssign = never

newlines.beforeTypeBounds

Since v3.0.0

This parameter controls formatting of bounds of type parameters: upper <:, lower >:, view <%, and context : bounds. It accepts the same values as newlines.source.

• classic: simply allows no line breaks (default; can't be specified)
• keep: preserves a no-break if the next bound fits on the line
• fold: uses a no-break if the next bound fits on the line
• unfold: puts all bounds on the same line, or breaks before each

newlines.alwaysBeforeElseAfterCurlyIf

Default: newlines.alwaysBeforeElseAfterCurlyIf = false

if (someCond) {
  foo()
}
else {
  bar()
}

if (someCond) {
  foo()
} else {
  bar()
}

Config for this example:

newlines.alwaysBeforeElseAfterCurlyIf = true

if (someCond) {
  foo()
} else {
  bar()
}

if (someCond) {
  foo()
}
else {
  bar()
}

Config for this example:

newlines.alwaysBeforeElseAfterCurlyIf = false

newlines.beforeCurlyLambdaParams

This parameter controls whether a newline is forced between the opening curly brace and the parameters of a lambda or partial function. Added in 2.7.0, replacing boolean alwaysBeforeCurlyBraceLambdaParams.

Default: newlines.beforeCurlyLambdaParams = "never"

// should keep one-line
x.map { x => s"${x._1} -> ${x._2}" }
x.map { case (c, i) => s"$c -> $i" }
// should break on arrow since case doesn't fit on a line
x.zipWithIndex.map { case (c, i) =>
  s"$c -> $i"
}
x.zipWithIndex.map { case (c, i) =>
  s"$c -> $i (long comment)"
}

// should keep one-line
x.map { x => s"${x._1} -> ${x._2}" }
x.map { case (c, i) => s"$c -> $i" }
// should break on arrow since case doesn't fit on a line
x.zipWithIndex.map { case (c, i) => s"$c -> $i" }
x.zipWithIndex.map { case (c, i) => s"$c -> $i (long comment)" }

Config for this example:

newlines.beforeCurlyLambdaParams = never

// should break on brace, though fits on the same line
x.map {
  x => s"${x._1} -> ${x._2}"
}
x.map {
  case (c, i) => s"$c -> $i"
}
x.zipWithIndex.map {
  case (c, i) =>
    s"$c -> $i (long comment)"
}
// should break on brace and arrow as lambda doesn't fit on a line
x.zipWithIndex.map {
  x =>
    s"${x._1} -> ${x._2} (long comment)"
}

// should break on brace, though fits on the same line
x.map { x => s"${x._1} -> ${x._2}" }
x.map { case (c, i) => s"$c -> $i" }
x.zipWithIndex.map { case (c, i) => s"$c -> $i (long comment)" }
// should break on brace and arrow as lambda doesn't fit on a line
x.zipWithIndex.map { x => s"${x._1} -> ${x._2} (long comment)" }

Config for this example:

newlines.beforeCurlyLambdaParams = always

// should keep one-line
x.map { x => s"${x._1} -> ${x._2}" }
x.map { case (c, i) => s"$c -> $i" }
// should break on brace as lambda doesn't fit on the same line
x.zipWithIndex.map {
  x => s"${x._1} -> ${x._2}"
}
x.zipWithIndex.map {
  case (c, i) => s"$c -> $i"
}
// should break on brace and arrow as lambda doesn't fit on a line
x.zipWithIndex.map {
  x =>
    s"${x._1} -> ${x._2} (long comment)"
}
x.zipWithIndex.map {
  case (c, i) =>
    s"$c -> $i (long comment)"
}

// should keep one-line
x.map { x => s"${x._1} -> ${x._2}" }
x.map { case (c, i) => s"$c -> $i" }
// should break on brace as lambda doesn't fit on the same line
x.zipWithIndex.map { x => s"${x._1} -> ${x._2}" }
x.zipWithIndex.map { case (c, i) => s"$c -> $i" }
// should break on brace and arrow as lambda doesn't fit on a line
x.zipWithIndex.map { x => s"${x._1} -> ${x._2} (long comment)" }
x.zipWithIndex.map { case (c, i) => s"$c -> $i (long comment)" }

Config for this example:

newlines.beforeCurlyLambdaParams = multiline

// should keep one-line
x.map { x => s"${x._1} -> ${x._2}" }
x.map { case (c, i) => s"$c -> $i" }
// should break after arrow as lambda doesn't fit on the same line
x.zipWithIndex.map { x =>
  s"${x._1} -> ${x._2}"
}
x.zipWithIndex.map { x =>
  s"${x._1} -> ${x._2} (long comment)"
}
// should break on brace as lambda doesn't fit on the same line
x.zipWithIndex.map {
  case (c, i) => s"$c -> $i"
}
// should break on brace and arrow as lambda doesn't fit on a line
x.zipWithIndex.map {
  case (c, i) =>
    s"$c -> $i (long comment)"
}

// should keep one-line
x.map { x => s"${x._1} -> ${x._2}" }
x.map { case (c, i) => s"$c -> $i" }
// should break after arrow as lambda doesn't fit on the same line
x.zipWithIndex.map { x => s"${x._1} -> ${x._2}" }
x.zipWithIndex.map { x => s"${x._1} -> ${x._2} (long comment)" }
// should break on brace as lambda doesn't fit on the same line
x.zipWithIndex.map { case (c, i) => s"$c -> $i" }
// should break on brace and arrow as lambda doesn't fit on a line
x.zipWithIndex.map { case (c, i) => s"$c -> $i (long comment)" }

Config for this example:

newlines.beforeCurlyLambdaParams = multilineWithCaseOnly

newlines.afterCurlyLambdaParams

This parameter controls handling of newlines after the arrow following the parameters of a curly brace lambda or partial function, and whether a space can be used for one-line formatting of the entire function body (if allowed but the body doesn't fit, a break is always forced).

This parameter was renamed in 2.7.0 from afterCurlyLambda, for clarity and consistency with beforeCurlyLambdaParams defined above.

Default: newlines.afterCurlyLambdaParams = "never"

// remove all blank lines if any
// one-line formatting is allowed
something.map { x => f(x) }

something.map { x => f(x) }

// remove all blank lines if any
// one-line formatting is allowed
something.map { x =>



  f(x)
}

something.map { x => f(x) }

Config for this example:

newlines.afterCurlyLambdaParams = squash

// remove all blank lines if any
// one-line formatting depends on newlines.source:
// yes for fold; no for unfold; otherwise, only if there was no break
something.map { x =>
  f(x)
}

something.map { x => f(x) }

// remove all blank lines if any
// one-line formatting depends on newlines.source:
// yes for fold; no for unfold; otherwise, only if there was no break
something.map { x =>



  f(x)
}

something.map { x => f(x) }

Config for this example:

newlines.afterCurlyLambdaParams = never

// if blank lines are present, keep only one
// one-line formatting depends on newlines.source:
// yes for fold; no for unfold; otherwise, only if there was no break
something.map { x =>

  f(x)
}

something.map { x => f(x) }

// if blank lines are present, keep only one
// one-line formatting depends on newlines.source:
// yes for fold; no for unfold; otherwise, only if there was no break
something.map { x =>



  f(x)
}

something.map { x => f(x) }

Config for this example:

newlines.afterCurlyLambdaParams = keep

// ensure a single blank line
// one-line formatting is not allowed
something.map { x =>

  f(x)
}

something.map { x =>

  f(x)
}

// ensure a single blank line
// one-line formatting is not allowed
something.map { x =>



  f(x)
}

something.map { x => f(x) }

Config for this example:

newlines.afterCurlyLambdaParams = always

newlines.implicitParamListModifierXXX

These parameters control newlines around implicit parameter list modifier.

Since v2.5.0.

Newlines around using parameter and argument list modifier

using soft keyword was introduced in Scala 3 and is supported in scalafmt. Besides parameter lists, using can also be used with argument lists hence provided rules will then also be applied to them.

Since v3.0.0.

The parameters defined below can also be accessed via their alternative names where implicit is replaced with using (for instance, newlines.usingParamListModifierPrefer). Whichever naming you use, formatting will be applied to both implicit and using.

Prefer After (default)

Prefers newline after implicit. Newline will be added unless the entire implicit parameter list fits on a line, or config style is false. Newline can also be added before if the keyword itself would overflow the line.

def format(code: String, age: Int)(implicit
    ev: Parser,
    c: Context
): String

def format(code: String, age: Int)(implicit ev: Parser, c: Context): String

Config for this example:

maxColumn = 60
newlines.implicitParamListModifierPrefer = after

Prefer Before

Prefers newline before implicit. Newline will not be added if the entire implicit parameter list fits on a line.

def format(code: String, age: Int)(
    implicit ev: Parser,
    c: Context
): String

def format(code: String, age: Int)(implicit ev: Parser, c: Context): String

Config for this example:

maxColumn = 60
newlines.implicitParamListModifierPrefer = before

Force Before

If set, forces newline before implicit. Otherwise, newline can still be added if the keyword would overflow the line.

def format(code: String, age: Int)(
    implicit ev: Parser,
    c: Context
): String

def format(code: String, age: Int)(implicit ev: Parser, c: Context): String

Config for this example:

maxColumn = 60
newlines.implicitParamListModifierForce = [before]

Force After

If set, forces newline after implicit. Otherwise, newline can still be added unless before is true, or the entire implicit parameter list fits on a line, or config style is false.

def format(code: String, age: Int)(implicit
    ev: Parser,
    c: Context
): String

def format(code: String, age: Int)(implicit ev: Parser, c: Context): String

Config for this example:

maxColumn = 60
newlines.implicitParamListModifierForce = [after]

Force both before and after

def format(code: String, age: Int)(
    implicit
    ev: Parser,
    c: Context
): String

def format(code: String, age: Int)(implicit ev: Parser, c: Context): String

Config for this example:

maxColumn = 60
newlines.implicitParamListModifierForce = [before,after]

Implicit with optIn.configStyleArguments

While config-style normally requires a newline after the opening parenthesis, postponing that break until after the implicit keyword is allowed if other parameters require keeping this keyword attached to the opening brace.

Therefore, any of the parameters described in this section will take precedence even when optIn.configStyleArguments = true is used.

newlines.afterInfix

Since v2.5.0.

This parameter (and its companions) controls formatting around infix expressions.

The default value depends on newlines.source (see below).

newlines.afterInfix=keep

This approach preserves line breaks in the input. This is the original behaviour, and default for newlines.source=classic,keep.

newlines.afterInfix=many,some

These approaches completely ignore existing newlines around infix, always use a space before an infix operator and occasionally break after it. some is default for newlines.source=fold, and many for newlines.source=unfold.

Might require increasing runner limits (runner.optimizer.maxVisitsPerToken, possibly even runner.maxStateVisits), to avoid SearchStateExploded exceptions.

some will introduce fewer line breaks than many. Both will attempt to break after higher-precedence operators, and both will always break before an expression enclosed in matching parentheses.

newlines.afterInfixMaxCountPerFile

Default: newlines.afterInfixMaxCountPerFile = 500

If the total number of infix operations in the entire file exceeds newlines.afterInfixMaxCountPerFile, the formatter automatically switches to newlines.afterInfix=keep for this file.

newlines.afterInfixMaxCountPerExprForSome

Default: newlines.afterInfixMaxCountPerExprForSome = 10

If newlines.afterInfix is set to some and the number of infix operations in a given expression sequence (top-level or enclosed in parens/braces) exceeds newlines.afterInfixMaxCountPerExprForSome, the formatter switches to many for that sequence only.

newlines.afterInfixBreakOnNested

Default: newlines.afterInfixBreakOnNested = false

If enabled, will force line breaks around a nested parenthesized sub-expression in a multi-line infix expression.

newlines.avoidForSimpleOverflow

A list parameter (of comma-separated flags), with possible flags described below. These flags relax formatting rules to allow occasional line overflow (i.e., when line exceeds maxColumn) in simple cases instead of introducing a newline.

Default: newlines.avoidForSimpleOverflow = []

newlines.avoidForSimpleOverflow=[tooLong]

Since v2.6.0.

This flag tries to avoid introducing a newline if the line would overflow even with a newline.

object Example {
  foo_bar_baz("the quick brown fox jumps over the lazy dog") {
    println("")
  }
  foo_bar_baz(
    "the quick brown fox jumps over a dog") {
    println("")
  }
}

object Example {
  foo_bar_baz("the quick brown fox jumps over the lazy dog") {
    println("")
  }
  foo_bar_baz("the quick brown fox jumps over a dog") {
    println("")
  }
}

Config for this example:

maxColumn = 50
danglingParentheses.callSite = false
newlines.avoidForSimpleOverflow = [tooLong]

newlines.avoidForSimpleOverflow=[punct]

Since v2.6.0.

This flag tries to avoid a newline if the line would overflow only because of trailing punctuation (non-alphanum symbols of length 1).

With the flag set:

class Engine[TD, EI, PD, Q, P, A](
    val dataSourceClassMap: Map[String, Class[_ <: BaseDataSource[TD, EI, Q, A]]]
) {}

class Engine[TD, EI, PD, Q, P, A](
    val dataSourceClassMap: Map[
      String,
      Class[_ <: BaseDataSource[TD, EI, Q, A]]]) {}

Config for this example:

maxColumn = 80
newlines.avoidForSimpleOverflow = [punct]

newlines.avoidForSimpleOverflow=[slc]

Since v3.0.0.

This flag tries to avoid a newline if the line would overflow only because of trailing single-line comment (one which starts with //).

intercept[TestException] {
  val ct = Thread.currentThread() // comment
}

intercept[TestException] {
  val ct = Thread.currentThread() // comment
}

Config for this example:

maxColumn = 40
newlines.avoidForSimpleOverflow = [slc]

intercept[TestException] {
  val ct =
    Thread.currentThread() // comment
}

intercept[TestException] {
  val ct = Thread.currentThread() // comment
}

Config for this example:

maxColumn = 40
newlines.avoidForSimpleOverflow = []

newlines.avoidInResultType

If true, newlines in definition result type will only be used if formatting without them is impossible. This parameter was added in 2.7.0, replacing neverInResultType.

Default: newlines.avoidInResultType = false

// no newlines in result type
def permissionState(
    a: A = js.native
): js.Promise[PushPermissionState] = js.native
// no newlines in result type
val permissionState
    : js.Promise[PushPermissionState] = js.native
// can't format without newlines
implicit protected val td: TildeArrow {
  type Out = RouteTestResult
} = TildeArrow.injectIntoRoute

// no newlines in result type
def permissionState(a: A = js.native): js.Promise[PushPermissionState] = js.native
// no newlines in result type
val permissionState: js.Promise[PushPermissionState] = js.native
// can't format without newlines
implicit protected val td: TildeArrow {
  type Out = RouteTestResult } = TildeArrow.injectIntoRoute

Config for this example:

maxColumn = 40
newlines.avoidInResultType = true
newlines.neverBeforeJsNative = true

newlines.sometimesBeforeColonInMethodReturnType

If true, in some rare cases a newline could be added before the colon which delimits the return type in a method signature.

Normally, this will only happen if formatting otherwise will lead to line overflow or the return type spanning too many lines.

Also, see newlines.beforeOpenParenXxxSite below.

Default: newlines.sometimesBeforeColonInMethodReturnType = true

def someVeryLongMethodName
    : Map[String, String] = ???

def someVeryLongMethodName: Map[String, String] = ???

Config for this example:

maxColumn = 40
newlines.sometimesBeforeColonInMethodReturnType = true

newlines.beforeOpenParenXxxSite

This parameter, if enabled, causes a parameter group which doesn't fit on the same line to be formatted separately, with a newline just before the opening parenthesis.

Since v3.0.0.

Use null (default) to disable it. Otherwise, takes the same values as newlines.source (or explicit source to mirror the current value of newlines.source).

Specific formatting depends on the value: for keep, will preserve a newline; for unfold, will format every parameter group separately unless all fit on a single line; fold will use a more compact formatting.

• beforeOpenParenDefnSite applies to definitions (methods, ctors, macros, etc.)
• beforeOpenParenCallSite applies to invocations (method calls) and is only supported for scala3

Additional nuances:

• if newlines.sometimesBeforeColonInMethodReturnType is true, a newline will be added before the colon unless the entire signature fits on a line (except when set to keep).
• if the corresponding align.openParenXxxSite is true, multi-line parameters will start on the same line as the opening parenthesis and align; otherwise, formatting will use a newline and an appropriate continuation indent.

# Defaults
newlines.beforeOpenParenDefnSite = null
newlines.beforeOpenParenCallSite = null

def fooFunc
  (foo1: String)
  (foo2: String,
   foo3: String
  )
  : String = ???
val res = fooFunc
  ("foo1")
  ("foo2", "foo3")

def fooFunc(foo1: String)(foo2: String, foo3: String): String = ???
val res = fooFunc("foo1")("foo2", "foo3")

Config for this example:

maxColumn = 20
runner.dialect = scala3 // for CallSite
align.openParenDefnSite = true
newlines {
  beforeOpenParenDefnSite = fold
  beforeOpenParenCallSite = unfold
  sometimesBeforeColonInMethodReturnType = true
}

def fooFunc
  (foo1: String)
  (
      foo2: String,
      foo3: String
  ): String = ???
val res = fooFunc
  ("foo1")
  ("foo2", "foo3")

def fooFunc(foo1: String)(foo2: String, foo3: String): String = ???
val res = fooFunc("foo1")("foo2", "foo3")

Config for this example:

maxColumn = 20
runner.dialect = scala3 // for CallSite
align.openParenCallSite = true
newlines {
  beforeOpenParenDefnSite = unfold
  beforeOpenParenCallSite = fold
  sometimesBeforeColonInMethodReturnType = false
}

newlines.selectChains

This parameter controls how select chains (sequences of .method invocations) are formatted.

It takes the same values as newlines.source; use null (default) to fall back on the current value of newlines.source.

Since v3.0.0.

• keep: attempts to preserve break
• fold: attempts to avoid breaks
• unfold: forces breaks on each select unless all fit on a single line
• classic (i.e., null and newlines.source is not specified): see Classic select chains.

Newlines: danglingParentheses

While this parameter is not technically under the newlines section, it logically belongs there.

danglingParentheses.defnSite

Default: danglingParentheses.defnSite = true

object a {
  // defnSite
  def method(
      a: Int,
      b: String
  ): Boolean

  // callSite
  method(
    argument1,
    argument2)
}

object a {
  // defnSite
  def method(a: Int, b: String): Boolean

  // callSite
  method(argument1, argument2)
}

Config for this example:

danglingParentheses.defnSite = true
danglingParentheses.callSite = false
maxColumn=25

danglingParentheses.callSite

Default: danglingParentheses.callSite = true

object a {
  // defnSite
  def method(
      a: Int,
      b: String): Boolean

  // callSite
  method(
    argument1,
    argument2
  )
}

object a {
  // defnSite
  def method(a: Int, b: String): Boolean

  // callSite
  method(argument1, argument2)
}

Config for this example:

danglingParentheses.defnSite = false
danglingParentheses.callSite = true
maxColumn=25

danglingParentheses.ctrlSite

Since v2.5.0.

Forces dangling on open/close parens around control structures (if, while, for) when line breaks must occur.

For optional braces in scala3, this parameter also controls whether to break before then or do in a multi-line condition.

Default: danglingParentheses.ctrlSite = true

if (something) {
  // nothing
}
if (
  something_else
) {
  // nothing
}

if (something) {
  // nothing
}
if (something_else) {
  // nothing
}

Config for this example:

danglingParentheses.ctrlSite = true
maxColumn=20

danglingParentheses.tupleSite

This parameter controls dangling of closing parentheses in tuples. If not specified, will use the value of danglingParentheses.callSite.

Since v3.0.0.

val i =
  ( //hello scalafmt, please don't blow up
    (1, 2),
    1,
    3,
    4,
    4
  )

val i =
          ( //hello scalafmt, please don't blow up
                   (1, 2),
                   1,
                   3,
                   4,
                   4)

Config for this example:

danglingParentheses.tupleSite = true

val i =
  ( //hello scalafmt, please don't blow up
    (1, 2),
    1,
    3,
    4,
    4)

val i =
          ( //hello scalafmt, please don't blow up
                   (1, 2),
                   1,
                   3,
                   4,
                   4)

Config for this example:

danglingParentheses.tupleSite = false

danglingParentheses.exclude

Since v2.5.0.

When the appropriate danglingParentheses flag (e.g., defnSite) has been set, this parameter can be used to limit contexts where dangling is applied (currently, class, trait, enum, extension and def are supported).

Default: danglingParentheses.exclude = []

def other(a: String, b: String)(
  c: String,
  d: String) = a + b + c
other(a, b)(c, d)

def other(a: String, b: String)(c: String, d: String) = a + b + c
other(a, b)(c, d)

Config for this example:

indent.defnSite = 2
danglingParentheses.defnSite = true
danglingParentheses.exclude = [def]

Newlines: Config-style formatting

This formatting applies to argument lists in class definitions and method calls. It normally involves a newline after the opening parenthesis (or after the implicit keyword) and a newline before the closing parenthesis.

As part of the formatting output, arguments are output one per line (but this is not used in determining whether the source uses config-style formatting).

While this parameter is not technically under the newlines section, it logically belongs there.

optIn.configStyleArguments

If true, applies config-style formatting:

• if single-line formatting is impossible
• if the source uses config-style and newlines.source = classic/keep
• if other parameters force config-style (see below)

Default: optIn.configStyleArguments = true

object a {
  // keeps single line
  def method1(a: Int, b: String): Boolean

  // forces config style
  def method2(
      a: Int,
      b: String,
      c: String
  ): Boolean

  // preserves config style
  def method3(
      a: Int,
      b: String,
      c: String
  ): Boolean
}

object a {
  // keeps single line
  def method1(a: Int, b: String): Boolean

  // forces config style
  def method2(a: Int, b: String, c: String): Boolean

  // preserves config style
  def method3(
    a: Int, b: String, c: String
  ): Boolean
}

Config for this example:

optIn.configStyleArguments = true
maxColumn=45

Forcing config style

Controls parameters which trigger forced config-style formatting. All conditions must be satisfied in order for this rule to apply.

# Defaults
runner.optimizer.forceConfigStyleOnOffset = 150
runner.optimizer.forceConfigStyleMinArgCount = 2

• runner.optimizer.forceConfigStyleOnOffset: applies to method calls; if positive, specifies the minimum character distance between the matching parentheses, excluding any whitespace
• runner.optimizer.forceConfigStyleMinArgCount applies to method calls; specifies the minimum number of arguments

object a {
  // this is a definition, not a method call
  def method(a: String, b: String = null): Boolean

  // keeps single line; min offset not satisfied
  method(a, b)

  // keeps single line; min arg not satisfied
  method(SomeVeryVeryVeryVeryLongArgument)

  // forces config style
  method(
    foo,
    bar
  )
}

object a {
  // this is a definition, not a method call
  def method(a: String, b: String = null): Boolean

  // keeps single line; min offset not satisfied
  method(a, b)

  // keeps single line; min arg not satisfied
  method(SomeVeryVeryVeryVeryLongArgument)

  // forces config style
  method(foo, bar)
}

Config for this example:

optIn.configStyleArguments = true
runner.optimizer.forceConfigStyleOnOffset = 5
runner.optimizer.forceConfigStyleMinArgCount = 2
maxColumn = 60

Rewrite Rules

To enable a rewrite rule, add it to the config like this rewrite.rules = [Imports].

AvoidInfix

This rule replaces infix expressions a op b with proper method calls a.op(b).

NB: The rule currently does not support right-associative operators (i.e., those which end in :) which would have had to be rewritten as b.op(a).

The rule takes the rewrite.neverInfix parameter group which consists of includeFilters and excludeFilters, two lists of regular expressions, which determine which operators are eligible for this rewrite.

a.success(b)
a.error(b, c)
a map { x =>
  x + 2
}
("o" % "a" % "v").c(D)
(future map { case e: Err =>
  0
}).recover(_.toString)
future.recover { case e: Err =>
  0
} map (_.toString)

a success b
a error (b, c)
a map { x =>
  x + 2
}
"o" % "a" % "v" c(D)
future map {
  case e: Err => 0
} recover (_.toString)
future recover {
  case e: Err => 0
} map (_.toString)

Config for this example:

rewrite.rules = [AvoidInfix]
rewrite.neverInfix.excludeFilters."+" = [ "map" ]

RedundantBraces

Warning. This rewrite can cause non-idempotent formatting, see #1055.

def foo =
  List(1, 2, 3).sum

def foo = {
  List(1, 2, 3).sum
}

Config for this example:

rewrite.rules = [RedundantBraces]

q"Hello $name"

q"Hello ${name}"

Config for this example:

rewrite.rules = [RedundantBraces]
rewrite.redundantBraces.stringInterpolation = true

List(1, 2, 3).map(x => x + 1)

List(1, 2, 3).map { x => x + 1 }

Config for this example:

rewrite.rules = [RedundantBraces]

Entire power of RedundantBraces can be accessed with newlines.afterCurlyLambdaParams=squash. It will try to squash lambda body in one line and then replace braces with parens:

List(1, 2, 3).map(x => x + 1)

List(1, 2, 3).map { x =>
  println("you can't squash me!")
  x + 1
}

List(1, 2, 3).map { x =>
  x + 1
}

List(1, 2, 3).map { x =>
  println("you can't squash me!")
  x + 1
}

Config for this example:

rewrite.rules = [RedundantBraces]
newlines.afterCurlyLambdaParams=squash

Configuration options

Default: rewrite.redundantBraces.generalExpressions = true

while (x < 10)
  x += 1

str match {
  case "a" =>
    println("ok")
  case _ =>
    println("not ok")
}

while (x < 10) {
  x += 1
}

str match {
  case "a" => {
    println("ok")
  }
  case _ => {
    println("not ok")
  }
}

Config for this example:

rewrite.rules = [RedundantBraces]
rewrite.redundantBraces.generalExpressions = true

Default: rewrite.redundantBraces.ifElseExpressions = false

if (a > b)
  doSomething()
else
  doAnything()

if (a > b) {
  doSomething()
} else {
  doAnything()
}

Config for this example:

rewrite.rules = [RedundantBraces]
rewrite.redundantBraces.ifElseExpressions = true

Default: rewrite.redundantBraces.methodBodies = true

def f() =
  1 + 1

def f() = {
  1 + 1
}

Config for this example:

rewrite.rules = [RedundantBraces]
rewrite.redundantBraces.methodBodies = true

Default: rewrite.redundantBraces.includeUnitMethods = true

Affects only functions with explicitly specified Unit type

def f() =
  1 + 1

def x(): Unit = {
  println("example")
}

def f() = {
  1 + 1
}

def x(): Unit = {
  println("example")
}

Config for this example:

rewrite.rules = [RedundantBraces]
rewrite.redundantBraces.methodBodies = true
rewrite.redundantBraces.includeUnitMethods = false

Default: rewrite.redundantBraces.stringInterpolation = false

s"user id is $id"

s"user id is ${id}"

Config for this example:

rewrite.rules = [RedundantBraces]
rewrite.redundantBraces.stringInterpolation = true

rewrite.redundantBraces.parensForOneLineApply is true by default for edition >= 2020-01. See also newlines.afterCurlyLambdaParams = squash.

xs.map(x => x + 1)

xs.map { x => x + 1 }

Config for this example:

rewrite.rules = [RedundantBraces]
rewrite.redundantBraces.parensForOneLineApply = true

Default: rewrite.redundantBraces.maxLines = 100

def f() =
  collection
    .map(x => x + 1)
    .filter(_ < 10)
    .map(_ * 2)

def f() = {
  collection
    .map(x => x + 1)
    .filter(_ < 10)
    .map(_ * 2)
    .headOption
}

def f() = {
  collection
    .map(x => x + 1)
    .filter(_ < 10)
    .map(_ * 2)
}

def f() = {
  collection
    .map(x => x + 1)
    .filter(_ < 10)
    .map(_ * 2)
    .headOption
}

Config for this example:

rewrite.rules = [RedundantBraces]
rewrite.redundantBraces.maxLines = 3

RedundantParens

for {
  a <- b
  if a.nonEmpty
} yield a

val z = insertData *> readDatabase(id)

for {
  a <- b
  if (a.nonEmpty)
} yield a

val z = (insertData *> readDatabase(id))

Config for this example:

rewrite.rules = [RedundantParens]

SortModifiers

Modifiers are sorted based on the given order. Affects modifiers of the following definitions: trait, class, object, type, and val+var, both as fields and class parameters.

implicit final private lazy val x = 42
implicit final private lazy val y = 42

final lazy private implicit val x = 42
lazy final implicit private val y = 42

Config for this example:

rewrite.rules = [SortModifiers]

class Test(implicit
    final private val i1: Int,
    final private val i2: String
)

class Test(
    implicit
    final private val i1: Int,
    private final val i2: String
)

Config for this example:

rewrite.rules = [SortModifiers]

sealed protected[X] trait ADT
final private case object A1 extends ADT
final private case class A2(a: Int)
    extends ADT

sealed protected[X] trait ADT
final private case object A1 extends ADT
private final case class A2(a: Int)
    extends ADT

Config for this example:

rewrite.rules = [SortModifiers]

If you choose the non-default sort order then you have to specify all eight modifiers in the order you wish to see them. Hint: since some modifiers are mutually exclusive, you might want to order them next to each other.

implicit final override val x = 2

override implicit final val x = 2

Config for this example:

rewrite.rules = [SortModifiers]
rewrite.sortModifiers.order = [
  "implicit", "final", "sealed", "abstract",
  "override", "private", "protected", "lazy"
]

PreferCurlyFors

Replaces parentheses into curly braces in for comprehensions that contain multiple enumerator generators.

for {
  a <- as
  b <- bs if b > 2
} yield (a, b)

for(a <- as; b <- bs if b > 2)
 yield (a, b)

Config for this example:

rewrite.rules = [PreferCurlyFors]

This rule accepts the following settings:

• rewrite.preferCurlyFors.removeTrailingSemicolonsOnly (default: false):
  • if false (default), replaces all semicolons with a newline
  • if true, keeps semicolons unless followed by a newline or single-line comment

Imports

This rule applies to import or, in Scala 3, also export statements found at the top level (source, package or class/object/trait level).

The logic also moves comments attached to each import statement or selector, as follows:

• all consecutive standalone comments before (no blank lines and not following some other token)
• the comment right after (possibly after a comma), on the same line
• only single-line (//) comments are supported; multiline (/*) comments will not be moved and in many cases will likely be removed instead

Since v3.0.0.

Imports: expand

This parameter will attempt to create a separate line for each selector within a {...}. It replaces the deprecated rule ExpandImportSelectors.

Default: rewrite.imports.expand = false

import a.b
import a.c
import h.k
import h.l

import d.e.f
import d.e.g
import a.{foo => bar, zzzz => _, _}

import a.{
    b,
    c
  }, h.{
    k, l
  }
import d.e.{f, g}
import a.{
    foo => bar,
    zzzz => _,
    _
  }

Config for this example:

rewrite.rules = [Imports]
rewrite.imports.expand = true

Imports: sort = none

This default option causes no sorting.

Imports: sort = original

Replaces the deprecated rule SortImports. The imports are sorted by the groups: symbols, lower-case, upper-case.

import foo.{bar, sand, Random, Zilch}

import foo.{Zilch, bar, Random, sand}

Config for this example:

rewrite.rules = [Imports]
rewrite.imports.sort = original

Imports: sort = ascii

Replaces the deprecated rule AsciiSortImports. The imports are sorted by their Ascii codes.

import foo.{Random, `symbol`, bar, ~>}

import foo.{~>, `symbol`, bar, Random}

Config for this example:

rewrite.rules = [Imports]
rewrite.imports.sort = ascii

Imports: sort = scalastyle

• Selectors are sorted in a case-insensitive manner (ascii on lowercase), except by first character as follows: non-wildcard symbols, lowercase, uppercase, wildcard.
• If grouping, import statements are also sorted using case-insensitive order, except by first character in every dot-separated label as follows: symbols (including wildcard), uppercase, lowercase.

import foo._
import foo.`qux`.{`symbol`, ~>, bar, Random}
import foo.Baz.{bar => xyz, _}
import foo.bar.{`symbol`, ~>, bar, Random}

import foo.bar.{Random, bar, ~>, `symbol`}
import foo.Baz.{bar => xyz, _}
import foo.`qux`.{Random, bar, ~>, `symbol`}
import foo._

Config for this example:

maxColumn = 50
rewrite.rules = [Imports]
rewrite.imports.sort = scalastyle
rewrite.imports.groups = [["foo\\..*"]]

Imports: groups

Keep in mind that this functionality should be used very carefully if hierarchical (relative) imports are allowed in your codebase. Groups should only refer to typical top-level domains such as java, org, com or scala, and sorting should be disabled.

The safest way to handle this case is by using scalafix with a semantic rule like OrganizeImports. However, on a large codebase, the overhead of using semantic scalafix rules might be substantial.

This rule will separate all import statements into groups. If sorting is enabled (i.e., not none), imports will also be sorted within each group.

The rule accepts the following parameters:

• rewrite.imports.groups: defines several sets of regular expressions; each set defines a single group, and the groups are output in the order they are configured (imports not matching any of the regexes will form their own group at the end). Regular expressions are applied to the entire parent domain of the import statement, up to and including the final dot.
• rewrite.imports.contiguousGroups (since v3.0.2):
  • if only (default), only consecutive import statements will be grouped
  • if no, grouping will happen on all imports within the same container (source, package, template etc.)

import foo.Baz.{bar => xyz, _}
import foo._
import foo.`qux`.{
  Random,
  `symbol`,
  bar,
  ~>
}

import bar._
import bar.`qux`.{
  Random,
  `symbol`,
  bar,
  ~>
}
import bar.bar.{
  Random,
  `symbol`,
  bar,
  ~>
}
import baz.Baz.{bar => xyz, _}
import baz._
import baz.bar.{
  Random,
  `symbol`,
  bar,
  ~>
}

import qux.Baz.{bar => xyz, _}
import qux.`qux`.{
  Random,
  `symbol`,
  bar,
  ~>
}
import qux.bar.{
  Random,
  `symbol`,
  bar,
  ~>
}

import bar.bar.{Random, bar, ~>, `symbol`}
import baz.Baz.{bar => xyz, _}
import qux.`qux`.{Random, bar, ~>, `symbol`}
import foo._
import baz.bar.{Random, bar, ~>, `symbol`}
import qux.Baz.{bar => xyz, _}
import foo.`qux`.{Random, bar, ~>, `symbol`}
import bar._
import qux.bar.{Random, bar, ~>, `symbol`}
import foo.Baz.{bar => xyz, _}
import bar.`qux`.{Random, bar, ~>, `symbol`}
import baz._

Config for this example:

rewrite.rules = [Imports]
rewrite.imports.sort = ascii
rewrite.imports.groups = [
  ["foo\\..*"],
  ["bar\\..*", "baz\\..*"]
]

Trailing commas

See SIP

The rule handles how trailing commas are treated in case of a dangling closing delimiter (parenthesis or bracket for definitions or invocations, brace for import statements only).

Regardless of the setting, trailing commas are always removed if the closing delimiter is not dangling (i.e., follows the final argument without a line break).

This logic is not triggered via the rewrite.rules parameter, but by setting trailingCommas.

Default: trailingCommas = "never"

Trailing commas: never

Makes sure there are no trailing commas:

import a.{b, c}
def method1(
    a: Int,
    b: Long
) = {}
def method2(
    a: Int,
    b: Long*
) = {}
def method3(
    a: Int
) = {}
method1(
  a,
  b
)
method2(
  a,
  b: _*
)
method3(
  a
)

import a.{
  b,
  c,
}
def method1(
  a: Int,
  b: Long,
) = {}
def method2(
  a: Int,
  b: Long*,
) = {}
def method3(
  a: Int,
) = {}
method1(
  a,
  b,
)
method2(
  a,
  b: _*,
)
method3(
  a,
)

Config for this example:

trailingCommas = never

Trailing commas: keep

Keeps any trailing commas:

import a.{b, c}
def method1(
    a: Int,
    b: Long,
) = {}
def method2(
    a: Int,
    b: Long*
) = {}
def method3(
    a: Int,
) = {}
method1(
  a,
  b
)
method2(
  a,
  b: _*,
)
method3(
  a,
)

import a.{
  b,
  c,
}
def method1(
  a: Int,
  b: Long,
) = {}
def method2(
  a: Int,
  b: Long*
) = {}
def method3(
  a: Int,
) = {}
method1(
  a,
  b
)
method2(
  a,
  b: _*,
)
method3(
  a,
)

Config for this example:

trailingCommas = keep

Trailing commas: always

Makes sure there are trailing commas:

import a.{b, c}
def method1(
    a: Int,
    b: Long,
) = {}
def method2(
    a: Int,
    b: Long*,
) = {}
def method3(
    a: Int,
) = {}
method1(
  a,
  b,
)
method2(
  a,
  b: _*,
)
method3(
  a,
)

import a.{
  b,
  c
}
def method1(
  a: Int,
  b: Long
) = {}
def method2(
  a: Int,
  b: Long*
) = {}
def method3(
  a: Int
) = {}
method1(
  a,
  b
)
method2(
  a,
  b: _*
)
method3(
  a
)

Config for this example:

trailingCommas = always

Trailing commas: multiple

Since v2.5.0.

Makes sure there are trailing commas for multiple-argument expressions only, except when the last argument is repeated:

import a.{b, c}
def method1(
    a: Int,
    b: Long,
) = {}
def method2(
    a: Int,
    b: Long*
) = {}
def method3(
    a: Int
) = {}
method1(
  a,
  b,
)
method2(
  a,
  b: _*
)
method3(
  a
)

import a.{
  b,
  c
}
def method1(
  a: Int,
  b: Long
) = {}
def method2(
  a: Int,
  b: Long*,
) = {}
def method3(
  a: Int,
) = {}
method1(
  a,
  b
)
method2(
  a,
  b: _*,
)
method3(
  a,
)

Config for this example:

trailingCommas = multiple

Scala3 rewrites

This section describes rules which are applied if the appropriate dialect (e.g., runner.dialect = scala3) is selected.

This logic is not triggered via the rewrite.rules parameter, but by setting parameters under rewrite.scala3 subsection.

rewrite.scala3.convertToNewSyntax

If this flag is enabled, the following new syntax will be applied:

• control syntax
• vararg splices
• imports

rewrite.scala3.removeOptionalBraces

If this flag is enabled, optional braces will be removed and significant indentation applied.

The flag takes the following values:

• no: disabled
• yes: applies to expressions using the new control syntax (or rewrite.scala3.convertToNewSyntax is set)
• oldSyntaxToo: applies also to expressions using deprecated syntax

rewrite.scala3.insertEndMarkerMinLines

If this flag is set to a positive value, when an expression containing an optional braces region spans at least as many lines and isn't followed by an end marker, one will be inserted.

We will not insert end markers if the statement is not part of a template body, or a multi-stat block. Doing so might turn a single-stat expression (which doesn't require significant indentation handling) into a multi-stat block.

rewrite.scala3.removeEndMarkerMaxLines

If this flag is set to a positive value, when an expression containing an optional braces region spans at most as many lines and is followed by a standalone end marker (i.e., no other tokens on that line, including comments), the line containing the end marker will be deleted.

We will not remove end markers if

• the statement is not part of a template body, or a block with at least 3 statements. Doing so might turn a multi-stat expression (which requires significant indentation handling) into a single-stat.
• there are comments before the end marker, as without the end marker they would be treated as outside of the optional-braces region.

Vertical Multiline

Since: v1.6.0.

If enabled this formats methods such that parameters are on their own line indented by indent.defnSite. Separation between parameter groups are indented by two spaces less than indent.defnSite. The return type is on its own line at the end.

This formatting is only triggered if the method definition exceeds the maxColumn value in width or if the number of arguments to the method exceeds the verticalMultiline.arityThreshold.

verticalMultiline.arityThreshold

Default: verticalMultiline.arityThreshold = 100

case class Foo(x: String)
case class Bar(
    x: String,
    y: String)
object A {
  def foo(
      x: String,
      y: String
    )
  def hello(
      how: String
    )(are: String
    )(you: String
    ) = how + are + you
}

case class Foo(x: String)
case class Bar(x: String, y: String)
object A {
  def foo(x: String, y: String)
  def hello(how: String)(are: String)(you: String) = how + are + you
}

Config for this example:

verticalMultiline.atDefnSite = true
verticalMultiline.arityThreshold = 2

verticalMultiline.newlineAfterOpenParen

Default: verticalMultiline.newlineAfterOpenParen = false

def other(
  a: String,
  b: String
)(
  c: String,
  d: String
) = a + b + c

def other(a: String, b: String)(c: String, d: String) = a + b + c

Config for this example:

indent.defnSite = 2
verticalMultiline.atDefnSite = true
verticalMultiline.arityThreshold = 2
verticalMultiline.newlineAfterOpenParen = true

verticalMultiline.excludeDanglingParens

This parameter has been deprecated, please use danglingParentheses.exclude. Keep in mind, though, that the new parameter is empty by default while the old one isn't, so to use empty exclude list, one must set the old verticalMultiline.excludeDanglingParens=[].

Default: verticalMultiline.excludeDanglingParens = ["class", "trait"]

def other(
  a: String,
  b: String
)(
  c: String,
  d: String) = a + b + c
other(a, b)(c, d)

def other(a: String, b: String)(c: String, d: String) = a + b + c
other(a, b)(c, d)

Config for this example:

indent.defnSite = 2
verticalMultiline.excludeDanglingParens = [def]
verticalMultiline.atDefnSite = true
verticalMultiline.arityThreshold = 2
verticalMultiline.newlineAfterOpenParen = true

Vertical multiline with implicit parameter lists

Also see the general section on implicit parameter lists.

Before only

def format(
    code: String,
    age: Int
  )(
    implicit ev: Parser,
    c: Context
  ): String

def format(code: String, age: Int)(implicit ev: Parser, c: Context): String

Config for this example:

maxColumn = 60
verticalMultiline.atDefnSite = true
newlines.implicitParamListModifierForce = [before]

After only

def format(
    code: String,
    age: Int
  )(implicit
    ev: Parser,
    c: Context
  ): String

def format(code: String, age: Int)(implicit ev: Parser, c: Context): String

Config for this example:

maxColumn = 60
verticalMultiline.atDefnSite = true
newlines.implicitParamListModifierForce = [after]

Before and after

def format(
    code: String,
    age: Int
  )(
    implicit
    ev: Parser,
    c: Context
  ): String

def format(code: String, age: Int)(implicit ev: Parser, c: Context): String

Config for this example:

maxColumn = 60
verticalMultiline.atDefnSite = true
newlines.implicitParamListModifierForce = [before,after]

Comment processing

comments.wrap

Since v2.6.0.

Allows wrapping comments exceeding maxColumn.

Default: comments.wrap = "no"

comments.wrap = standalone

A standalone comment is one which is surrounded by line breaks.

/* long multiline
 * comment */
/* long singleline
 * comment */
val a = 1 // short
val b =
  2 // long singleline comment

/* long multiline comment */
// long singleline comment
val a = 1 // short
val b = 2 // long singleline comment

Config for this example:

maxColumn = 20
comments.wrap = standalone

comments.wrap = trailing

A trailing comment is one which is followed by a line break.

/* long multiline
 * comment */
/* long singleline
 * comment */
val a = 1 // short
val b =
  2 /* long
   * singleline
   * comment */

/* long multiline comment */
// long singleline comment
val a = 1 // short
val b = 2 // long singleline comment

Config for this example:

maxColumn = 20
comments.wrap = trailing

comments.wrapStandaloneSlcAsSlc

Since v2.6.0.

This parameter allows formatting a standalone single-line comment (i.e., //) to be wrapped using the same type, not a multi-line comment (/* ... */).

Default: comments.wrapStandaloneSlcAsSlc = false

// long singleline
// comment
val b =
  2 /* long
   * singleline
   * comment */

// long singleline comment
val b = 2 // long singleline comment

Config for this example:

maxColumn = 20
comments.wrap = trailing
comments.wrapStandaloneSlcAsSlc = true

docstrings.style

Since v2.6.0.

Default: docstrings.style = "SpaceAsterisk"

docstrings.style = keep

Prohibits formatting of docstrings. All other docstrings parameters are ignored.

Since v3.0.0.

/**   do not touch
 * this style
  * keep the text as-is
*/

/**   do not touch
 * this style
  * keep the text as-is
*/

Config for this example:

docstrings.style = keep

docstrings.style = Asterisk

This variant used to be called JavaDoc.

/**
 * Skip first line, format intermediate
 * lines with an asterisk below the
 * first asterisk of the first line (aka
 * JavaDoc)
 */

/** Skip first line, format intermediate lines with an asterisk
  * below the first asterisk of the first line (aka JavaDoc)
  */

Config for this example:

docstrings.style = Asterisk

docstrings.style = SpaceAsterisk

This variant used to be called ScalaDoc.

/** Format intermediate lines with a
  * space and an asterisk, both below
  * the two asterisks of the first line
  */

/** Format intermediate lines with a space and an asterisk,
 * both below the two asterisks of the first line
 */

Config for this example:

docstrings.style = SpaceAsterisk

docstrings.style = AsteriskSpace

/** Format intermediate lines with an
 *  asterisk and a space, both below the
 *  two asterisks of the first line
 */

/** Format intermediate lines with an asterisk and a space,
  * both below the two asterisks of the first line
  */

Config for this example:

docstrings.style = AsteriskSpace

docstrings.removeEmpty

If set, will cause empty docstrings to be removed.

Since v3.0.4.

Default: docstrings.removeEmpty = false

/** */
val a = 1

/** */
/**
  *
  */
/** */ /** */
val a = 1

Config for this example:

docstrings.removeEmpty = true

docstrings.oneline

Since v2.6.0. Ignored for docstrings.style = keep.

Default: docstrings.oneline = "keep"

docstrings.oneline = fold

/** Scaladoc oneline */
/** Scaladoc multiline */
val a = 1

/** Scaladoc oneline */
/**
  * Scaladoc multiline
  */
val a = 1

Config for this example:

docstrings.style = Asterisk
docstrings.oneline = fold

docstrings.oneline = unfold

/**
 * Scaladoc oneline
 */
/**
 * Scaladoc multiline
 */
val a = 1

/** Scaladoc oneline */
/**
  * Scaladoc multiline
  */
val a = 1

Config for this example:

docstrings.style = Asterisk
docstrings.oneline = unfold

docstrings.oneline = keep

/** Scaladoc oneline */
/**
 * Scaladoc multiline
 */
val a = 1

/** Scaladoc oneline */
/**
  * Scaladoc multiline
  */
val a = 1

Config for this example:

docstrings.style = Asterisk
docstrings.oneline = keep

docstrings.wrap

Will parse scaladoc comments and reformat them.

This functionality is generally limited to standard scaladoc elements and might lead to undesirable results in corner cases; for instance, the scaladoc parser doesn't have proper support of embedded HTML.

However, tables are supported.

Since v2.6.0. Ignored for docstrings.style = keep.

Default: docstrings.wrap = "yes"

/** @param d
  *   the Double to square,
  *   meaning multiply by
  *   itself
  * @return
  *   the result of squaring d
  *
  * Thus
  *   - if [[d]] represents a
  *     negative value:
  *     a. the result will be
  *        positive
  *     a. the value will be
  *        {{{d * d}}}
  *     a. it will be the same
  *        as for `-d`
  *   - however, if [[d]] is
  *     positive
  *     - the value will still
  *       be {{{d * d}}}
  *       - i.e., the same as
  *         {{{(-d) * (-d)}}}
  *
  * In other words:
  * {{{
  *     res = d * d
  *         = (-d) * (-d)
  * }}}
  */
def pow2(d: Double): Double

/**
 * @param d the Double to square, meaning multiply by itself
 * @return the result of squaring d
 *
 * Thus
 * - if [[d]] represents a negative value:
 *  a. the result will be positive
 *  a. the value will be {{{d * d}}}
 *  a. it will be the same as for `-d`
 * - however, if [[d]] is positive
 *  - the value will still be {{{d * d}}}
 *    - i.e., the same as {{{(-d) * (-d)}}}
 *
 * In other words:
 * {{{
 *    res = d * d
 *        = (-d) * (-d) }}}
 */
def pow2(d: Double): Double

Config for this example:

docstrings.wrap = yes
maxColumn = 30

docstrings.wrapMaxColumn

If wrapping (or applying oneline), allows specifying a different value than the default maxColumn.

docstrings.blankFirstLine

Controls whether to force the first line to be blank in a multiline docstring. Keep in mind that some combinations of parameters are prohibited (e.g., blankFirstLine=keep contradicts with style=Asterisk).

Since v2.7.5. Ignored for docstrings.style = keep or docstrings.wrap = no.

Default: docstrings.blankFirstLine = "no"

/** Scaladoc oneline */
/** Scaladoc multiline1
  */
/** Scaladoc multiline2
  */
val a = 1

/** Scaladoc oneline */
/** Scaladoc multiline1
  */
/**
  * Scaladoc multiline2
  */
val a = 1

Config for this example:

# do not force a blank first line
docstrings.blankFirstLine = no
docstrings.style = SpaceAsterisk
maxColumn = 30

/** Scaladoc oneline */
/**
  * Scaladoc multiline1
  */
/**
  * Scaladoc multiline2
  */
val a = 1

/** Scaladoc oneline */
/** Scaladoc multiline1
  */
/**
  * Scaladoc multiline2
  */
val a = 1

Config for this example:

# force a blank first line
docstrings.blankFirstLine = yes
docstrings.style = SpaceAsterisk
maxColumn = 30

/** Scaladoc oneline */
/** Scaladoc multiline1
  */
/** Scaladoc multiline2
  */
val a = 1

/** Scaladoc oneline */
/** Scaladoc multiline1
  */
/**
  * Scaladoc multiline2
  */
val a = 1

Config for this example:

# preserve a blank first line
docstrings.blankFirstLine = keep
docstrings.style = SpaceAsterisk
maxColumn = 30

Disabling or customizing formatting

For code block

There is a possibility to override scalafmt config for a specific code with // scalafmt: {} comment:

// scalafmt: { align.preset = most, danglingParentheses.preset = false }
libraryDependencies ++= Seq(
  "org.scalameta"  %% "scalameta"  % scalametaV,
  "org.scalacheck" %% "scalacheck" % scalacheckV)

// scalafmt: { align.preset = some, danglingParentheses.preset = true } (back to defaults)
libraryDependencies ++= Seq(
  "org.scalameta" %% "scalameta" % scalametaV,
  "org.scalacheck" %% "scalacheck" % scalacheckV
)

// scalafmt: { align.preset = most, danglingParentheses.preset = false }
libraryDependencies ++= Seq(
  "org.scalameta" %% "scalameta" % scalametaV,
  "org.scalacheck" %% "scalacheck" % scalacheckV)

// scalafmt: { align.preset = some, danglingParentheses.preset = true } (back to defaults)
libraryDependencies ++= Seq(
  "org.scalameta" %% "scalameta" % scalametaV,
  "org.scalacheck" %% "scalacheck" % scalacheckV)

// format: off

Disable formatting for specific regions of code by wrapping them in // format: off blocks:

// format: off
val identity = Array(1, 0, 0,
                     0, 1, 0,
                     0, 0, 1)
// format: on

// format: off
val identity = Array(1, 0, 0,
                     0, 1, 0,
                     0, 0, 1)
// format: on

Project

Configure which source files should be formatted in this project.

project.git

If this boolean flag is set, only format files tracked by git.

project.include/exclude

Since v3.0.0.

# Defaults
project.includePaths = ["glob:**.scala", "glob:**.sbt", "glob:**.sc"]
project.excludePaths = []

Allows specifying PathMatcher selection patterns to identify further which files are to be formatted (explicit glob: or regex: prefixes are required; keep in mind that PathMatcher patterns must match the entire path).

For instance,

project {
  includePaths = [
    "glob:**.scala",
    "regex:.*\\.sc"
  ]
  excludePaths = [
    "glob:**/src/test/scala/**.scala"
  ]
}

fileOverride

Since v2.5.0.

Allows specifying an additional subset of parameters for each file matching a PathMatcher pattern. For instance,

align.preset = none
fileOverride {
  "glob:**/*.sbt" {
    align.preset = most
  }
  "glob:**/src/test/scala/**/*.scala" {
    maxColumn = 120
    binPack.unsafeCallSite = true
  }
}

uses align.preset=none for all files except .sbt for which align.preset=most will apply. It will also use different parameters for test suites.

This parameter does not modify which files are formatted.

Spaces

spaces.beforeContextBoundColon

Default: spaces.beforeContextBoundColon = "Never"

def method[A: Bound]: B
def method[A: Bound]: B
def method[A: Bound: Bound2]: B

def method[A: Bound]: B
def method[A : Bound]: B
def method[A: Bound: Bound2]: B

Config for this example:

spaces.beforeContextBoundColon=Never

def method[A : Bound]: B
def method[A : Bound]: B
def method[A : Bound : Bound2]: B

def method[A: Bound]: B
def method[A : Bound]: B
def method[A: Bound: Bound2]: B

Config for this example:

spaces.beforeContextBoundColon=Always

def method[A: Bound]: B
def method[A: Bound]: B
def method[A : Bound : Bound2]: B

def method[A: Bound]: B
def method[A : Bound]: B
def method[A: Bound: Bound2]: B

Config for this example:

spaces.beforeContextBoundColon=IfMultipleBounds

spaces.inImportCurlyBraces

Default: spaces.inImportCurlyBraces = false

import a.b.{ c, d }

import a.b.{c, d}

Config for this example:

spaces.inImportCurlyBraces=true

spaces.inInterpolatedStringCurlyBraces

Since v3.0.0.

Default: spaces.inInterpolatedStringCurlyBraces = false

s"Hello ${ the } world!"
s"Hello ${ th.e } world!"
s"Hello ${ the() } world!"

s"Hello ${the} world!"
s"Hello ${ th.e} world!"
s"Hello ${the() } world!"

Config for this example:

spaces.inInterpolatedStringCurlyBraces = true

s"Hello ${oneHundred}% world!"
s"Hello ${th.e} world!"
s"Hello ${the()} world!"

s"Hello ${ oneHundred }% world!"
s"Hello ${ th.e} world!"
s"Hello ${the() } world!"

Config for this example:

spaces.inInterpolatedStringCurlyBraces = false

spaces.inParentheses

Default: spaces.inParentheses = false

foo( a, b )

foo(a, b)

Config for this example:

spaces.inParentheses=true

spaces.neverAroundInfixTypes

Default: spaces.neverAroundInfixTypes = []

def f: Foo##Repr
def g: Foo \/ Repr
// usage same operator not as type
def e = a ## b

def f: Foo##Repr
def g: Foo\/Repr
// usage same operator not as type
def e = a##b

Config for this example:

spaces.neverAroundInfixTypes=["##"]

spaces.afterKeywordBeforeParen

Default: spaces.afterKeywordBeforeParen = true

if(a) println("HELLO!")
while(a) println("HELLO!")

if (a) println("HELLO!")
while (a) println("HELLO!")

Config for this example:

spaces.afterKeywordBeforeParen = false

spaces.inByNameTypes

Default: spaces.inByNameTypes = true

def foo(a: =>A): A

def foo(a: => A): A

Config for this example:

spaces.inByNameTypes = false

spaces.afterSymbolicDefs

Default: spaces.afterSymbolicDefs = false

def +++ (a: A): F[A]

def +++(a: A): F[A]

Config for this example:

spaces.afterSymbolicDefs=true

Literals

Since v2.5.0.

Scalafmt allows flexible configuration of Integer and Floating Point literals formatting.

Default formatting:

123L
0xfff
0x1abL
10e-1
10e-1d

123l
0XFff
0x1Abl
10E-1
10e-1D

Each literals.* setting has three available options: Upper, Lower, Unchanged.

literals.long

Default: literals.long = "Upper"

Responsible for the case of Long literals suffix L

123L

123l

Config for this example:

literals.long=Upper

literals.float

Default: literals.float = "Lower"

Responsible for the case of Float literals suffix F

42.0f

42.0F

Config for this example:

literals.float=Lower

literals.double

Default: literals.double = "Lower"

Responsible for the case of Double literals suffix D

42.0d

42.0d

Config for this example:

literals.double=Lower

literals.hexPrefix

Default: literals.hexPrefix = "Lower"

Responsible for the case of hex integer literals prefix 0x

0x123

0X123

Config for this example:

literals.hexPrefix=Lower

literals.hexDigits

Default: literals.hexDigits = "Lower"

Responsible for the case of hex integer literals digits

0xaaaa
0xaaaaL

0xaAaA
0xaAaAl

Config for this example:

literals.hexDigits=Lower
literals.long=Upper

literals.scientific

Default: literals.scientific = "Lower"

Responsible for the case of Double literals exponent part

10E-1
10E-1f

10e-1
10e-1f

Config for this example:

literals.scientific=Upper
literals.float=Lower

XML

Controls formatting of Scala embedded within XML.

xmlLiterals.assumeFormatted

Since v2.6.0.

If set, formats embedded Scala relative to containing XML, making the assumption that XML itself is properly formatted. Otherwise, formatting is relative to the outer Scala code which contains the XML literals.

Default: xmlLiterals.assumeFormatted = false

object Example2 {
  def apply() = {
      <foo>
        <bar>{
          (1 + 2 + 3).toString(
            "some long format"
          )
        }</bar>
      </foo>
  }
}

object Example2 {
  def apply() = {
      <foo>
        <bar>{ (1 + 2 + 3).toString("some long format") }</bar>
      </foo>
  }
}

Config for this example:

maxColumn = 40
xmlLiterals.assumeFormatted = true

object Example2 {
  def apply() = {
    <foo>
        <bar>{
      (1 + 2 + 3).toString(
        "some long format"
      )
    }</bar>
      </foo>
  }
}

object Example2 {
  def apply() = {
      <foo>
        <bar>{ (1 + 2 + 3).toString("some long format") }</bar>
      </foo>
  }
}

Config for this example:

maxColumn = 40
xmlLiterals.assumeFormatted = false

Binpacking

binPack.literalArgumentLists

Default: binPack.literalArgumentLists = true

val secret: List[Bit] = List(0, 0, 1, 1,
  1, 0, 1, 0, 1, 1, 1, 0, 0, 1, 1, 0, 1,
  0, 1, 1, 1, 0, 0, 1, 0, 0, 1, 0, 0, 0,
  1, 0, 0, 0, 1, 0, 1)

val secret: List[Bit] = List(0, 0, 1, 1, 1, 0, 1, 0, 1, 1, 1, 0, 0, 1, 1, 0, 1,
  0, 1, 1, 1, 0, 0, 1, 0, 0, 1, 0, 0, 0, 1, 0, 0, 0, 1, 0, 1)

Config for this example:

binPack.literalArgumentLists = true

val secret: List[Bit] = List(
  0,
  0,
  1,
  1,
  1,
  1,
  1,
  0,
  0,
  1,
  1,
  0,
  1
)

val secret: List[Bit] = List(0, 0, 1, 1, 1, 1, 1, 0, 0, 1, 1, 0, 1)

Config for this example:

binPack.literalArgumentLists = false

val secret: List[Bit] = List(
  0, 0, 1, 1, 1, 0, 1, 0, 1, 1, 1, 0, 0, 1, 1, 0, 1, 0, 1, 1, 1, 0, 0, 1, 0, 0, 1, 0, 0, 0, 1, 0, 0, 0, 1, 0, 1)

val secret: List[Bit] = List(0, 0, 1, 1, 1, 0, 1, 0, 1, 1, 1, 0, 0, 1, 1, 0, 1,
  0, 1, 1, 1, 0, 0, 1, 0, 0, 1, 0, 0, 0, 1, 0, 0, 0, 1, 0, 1)

Config for this example:

binPack.literalArgumentLists = true
binPack.literalsSingleLine = true

See also:

• binPack.literalsIncludeSimpleExpr (to allow a few select methods followed by a few nested single-argument apply calls, with literals as arguments); added in v2.5.0
• all other binPack.literalXXX parameters (see list at the bottom) are self-explanatory.

binPack.parentConstructors

Parent constructors are C and D in class A extends B with C and D. Changed from a boolean to a wider set of options in v2.6.0.

Default: binPack.parentConstructors = "source"

The behaviour of binPack.parentConstructors = source depends on the value of newlines.source; keep maps to keep and attempts to preserve the space if there's no line break in the source, fold maps to Oneline, rest to Never.

object A {
  trait Foo
      extends Bar with Baz
}

object A {
  trait Foo
  extends Bar
  with Baz
}

Config for this example:

binPack.parentConstructors = Always
maxColumn = 30

object A {
  trait Foo
      extends Bar
      with Baz
}

object A {
  trait Foo extends Bar with Baz
}

Config for this example:

binPack.parentConstructors = Never
maxColumn = 30

object A {
  class Foo(a: Int)
      extends Bar with Baz

  class Foo(
      a: Int
  ) extends Bar with Baz
}

object A {
  class Foo(a: Int)
  extends Bar
  with Baz

  class Foo(
    a: Int
  )
  extends Bar
  with Baz
}

Config for this example:

binPack.parentConstructors = Oneline
maxColumn = 30

object A {
  class Foo(a: Int, b: Int)
      extends Bar with Baz

  class Foo(
      a: Int,
      b: Int
  ) extends Bar
      with Baz
}

object A {
  class Foo(a: Int, b: Int)
  extends Bar
  with Baz

  class Foo(
    a: Int,
    b: Int
  ) extends Bar with Baz
}

Config for this example:

binPack.parentConstructors = OnelineIfPrimaryOneline
maxColumn = 30

object A {
  class Foo(a: Int, b: Int) extends Bar(
        a,
        b
      ) with Baz
      with Qux
}

object A {
  class Foo(a: Int, b: Int) extends Bar(
    a,
    b
  ) with Baz
  with Qux
}

Config for this example:

binPack.parentConstructors = keep

binPack.unsafeXxxSite

Controls binpacking around defn or call sites. The following parameter values are supported since v3.0.0:

• Never disables the functionality (also takes false)
• Always enables the functionality (also takes true)
• Oneline ensures multiline arguments are not binpacked

binPack.bracketXxxSite

Since v3.0.4.

If set explicitly, will be used for type arguments or parameters, instead of the respective binPack.unsafeXxxSite.

Classic select chains

The parameters below control formatting of select chains when newlines.source = classic, and specifically which select expressions are included in a chain.

Generally, a chain can either be formatted on one line up to the last select, or will have a break on the first select.

includeCurlyBraceInSelectChains

Controls if select followed by curly braces can start a chain.

Default: includeCurlyBraceInSelectChains = true

List(1)
  .map { x =>
    x + 2
  }
  .filter(_ > 2)

List(1).map { x =>
    x + 2
  }
  .filter(_ > 2)

Config for this example:

includeCurlyBraceInSelectChains = true

List(1).map { x =>
  x + 2
}
  .filter(_ > 2)

List(1)
  .map { x =>
    x + 2
  }
  .filter(_ > 2)

Config for this example:

includeCurlyBraceInSelectChains = false

includeNoParensInSelectChains

Controls if select not followed by an apply can start a chain.

Default: includeNoParensInSelectChains = false

List(1)
  .toIterator
  .buffered
  .map(_ + 2)
  .filter(_ > 2)

List(1).toIterator.buffered
  .map(_ + 2)
  .filter(_ > 2)

Config for this example:

includeNoParensInSelectChains = true

List(1).toIterator.buffered
  .map(_ + 2)
  .filter(_ > 2)

List(1).toIterator.buffered.map(_ + 2).filter(_ > 2)

Config for this example:

includeNoParensInSelectChains = false

optIn.breakChainOnFirstMethodDot

Keeps the break on the first select of the chain if the source contained one. Has no effect if there was no newline in the source.

Default: optIn.breakChainOnFirstMethodDot = true

// collapse into a single line
foo.map(_ + 1).filter(_ > 2)

// collapse into a single line
foo
  .map(_ + 1)
  .filter(_ > 2)

Config for this example:

optIn.breakChainOnFirstMethodDot = false

// preserve break on first dot and break on subsequent dots
foo
  .map(_ + 1)
  .filter(_ > 2)

// preserve break on first dot and break on subsequent dots
foo
  .map(_ + 1).filter(_ > 2)

Config for this example:

optIn.breakChainOnFirstMethodDot = true

optIn.breaksInsideChains

Controls whether to preserve a newline before each subsequent select when the very first one used a line break; that is, this parameter doesn't prohibit single-line formatting even if there are source breaks down the chain.

If false, each subsequent select within the chain will behave exactly like the first, that is, either the entire chain will be formatted on one line, or will contain a break on every select.

If true, preserves existence or lack of breaks on subsequent selects if the first select was formatted with a newline.

Default: optIn.breaksInsideChains = false

foo
  .bar(_ + 1)
  .baz(_ > 2).qux
foo.bar(_ + 1).baz(_ > 2).qux
foo
  .bar(_ + 1).baz(_ > 2).qux(
    _ * 12
  )
foo.bar(_ + 1).baz(_ > 2).qux {
  _ * 12
}
foo
  .bar(_ + 1)
  .baz(_ > 2).qux(_ * 12)

foo.bar(_ + 1)
  .baz(_ > 2).qux
foo.bar(_ + 1).baz(_ > 2).qux
foo.bar(_ + 1).baz(_ > 2).qux(_ * 12)
foo.bar(_ + 1).baz(_ > 2).qux { _ * 12 }
foo.bar(_ + 1)
  .baz(_ > 2).qux(_ * 12)

Config for this example:

optIn.breaksInsideChains = true
maxColumn = 35

foo
  .bar(_ + 1)
  .baz(_ > 2)
  .qux
foo.bar(_ + 1).baz(_ > 2).qux
foo
  .bar(_ + 1)
  .baz(_ > 2)
  .qux(_ * 12)
foo.bar(_ + 1).baz(_ > 2).qux {
  _ * 12
}
foo
  .bar(_ + 1)
  .baz(_ > 2)
  .qux(_ * 12)

foo.bar(_ + 1)
  .baz(_ > 2).qux
foo.bar(_ + 1).baz(_ > 2).qux
foo.bar(_ + 1).baz(_ > 2).qux(_ * 12)
foo.bar(_ + 1).baz(_ > 2).qux { _ * 12 }
foo.bar(_ + 1)
  .baz(_ > 2).qux(_ * 12)

Config for this example:

optIn.breaksInsideChains = false
maxColumn = 35

optIn.encloseClassicChains

Controls what happens if a chain enclosed in parentheses is followed by additional selects. Those additional selects will be considered part of the enclosed chain if and only if this flag is false.

Since v2.6.2.

Default: optIn.encloseClassicChains = false

(foo.map(_ + 1).map(_ + 1))
  .filter(_ > 2)

(foo.map(_ + 1).map(_ + 1))
  .filter(_ > 2)

Config for this example:

optIn.encloseClassicChains = true
maxColumn = 30

(foo
  .map(_ + 1)
  .map(_ + 1))
  .filter(_ > 2)

(foo.map(_ + 1).map(_ + 1))
  .filter(_ > 2)

Config for this example:

optIn.encloseClassicChains = false
maxColumn = 30

Miscellaneous

optIn.forceBlankLineBeforeDocstring

If true, always insert a blank line before docstrings;
If false, preserves blank line only if one exists before.

Default: optIn.forceBlankLineBeforeDocstring = true

object Stuff {

  /** Some function */
  def hello = ()
}

object Stuff {
  /** Some function */
  def hello = ()
}

Config for this example:

optIn.forceBlankLineBeforeDocstring = true

object Stuff {
  /** Some function */
  def hello = ()
}

object Stuff {
  /** Some function */
  def hello = ()
}

Config for this example:

optIn.forceBlankLineBeforeDocstring = false

rewriteTokens

Map of tokens to rewrite. For example, Map("⇒" -> "=>") will rewrite unicode arrows to regular ascii arrows.

Default: rewriteTokens = {}

val tuple = "a" -> 1
val lambda = (x: Int) => x + 1
for {
  a <- Option(1)
  b <- Option(2)
} yield a + b

val tuple = "a" → 1
val lambda = (x: Int) ⇒ x + 1
for {
  a ← Option(1)
  b ← Option(2)
} yield a + b

Config for this example:

rewriteTokens = {
  "⇒": "=>"
  "→": "->"
  "←": "<-"
}

importSelectors

This parameter controls formatting of imports.

Default: importSelectors = "noBinPack"

import a.b.{
  c,
  d,
  e,
  f,
  g
}

import a.b.{c, d, e, f, g}

Config for this example:

maxColumn = 10
importSelectors = noBinPack

import a.b.{
  c, d, e,
  f, g
}

import a.b.{c, d, e, f, g}

Config for this example:

maxColumn = 10
importSelectors = binPack

import a.b.{c, d, e, f, g}

import a.b.{c, d, e, f, g}

Config for this example:

maxColumn = 10
importSelectors = singleLine

Markdown Formatting

Since v3.0.0.

Will format all scala mdoc fences inside Markdown files.

# Format default filetypes + Markdown files
project.includePaths."+" = ["glob:**.md"]

# *Only* format Markdown files
project.includePaths = [ "glob:**.md" ]

Before:

Markdown prose beginning.

```scala mdoc
val x  =       3
```

Markdown prose end.

After:

Markdown prose beginning.

```scala mdoc
val x = 3
```

Markdown prose end.

Edition

Removed in 2.7.0

Editions are no longer used. They were kept for backwards compatibility with old configuration files but new changes to the default Scalafmt formatting behavior will not respect the edition setting.

Other

To find all available configuration options, it's best to browse the source code of Scalafmt. A good place to start is ScalafmtConfig. Observe that this listing below is the top-level, there are more configuration options if you visited nested fields like spaces and newlines.

The values for parameters below are purely for informational purposes. They use pseudo-formatting similar to but incompatible with scalafmt.conf. Some of them show values which can't be explicitly specified.

version = "3.0.4"
maxColumn = 80
docstrings.oneline = keep
docstrings.removeEmpty = false
docstrings.wrap = yes
docstrings.wrapMaxColumn = null
docstrings.blankFirstLine = no
docstrings.style = SpaceAsterisk
comments.wrap = no
comments.wrapStandaloneSlcAsSlc = false
optIn.configStyleArguments = true
optIn.breaksInsideChains = false
optIn.breakChainOnFirstMethodDot = true
optIn.encloseClassicChains = false
optIn.selfAnnotationNewline = true
optIn.annotationNewlines = true
optIn.forceBlankLineBeforeDocstring = true
optIn.blankLineBeforeDocstring = false
binPack.unsafeCallSite = Never
binPack.unsafeDefnSite = Never
binPack.bracketCallSite = null
binPack.bracketDefnSite = null
binPack.indentCallSiteOnce = false
binPack.parentConstructors = source
binPack.literalArgumentLists = true
binPack.literalsIncludeSimpleExpr = false
binPack.literalsSingleLine = false
binPack.literalsMinArgCount = 5
binPack.literalsInclude = [
  ".*"
]
binPack.literalsExclude = [
  String
  "Term.Name"
]
indent.main = 2
indent.significant = null
indent.callSite = 2
indent.ctrlSite = null
indent.defnSite = 4
indent.caseSite = 4
indent.ctorSite = null
indent.extraBeforeOpenParenDefnSite = 0
indent.extendSite = 4
indent.withSiteRelativeToExtends = 0
indent.commaSiteRelativeToExtends = 2
align.allowOverflow = false
align.multiline = false
align.stripMargin = true
align.closeParenSite = false
align.openBracketCallSite = null
align.openParenCallSite = false
align.openParenCtrlSite = false
align.openBracketDefnSite = null
align.openParenDefnSite = false
align.openParenTupleSite = null
align.tokens = [
  {
    code = "=>"
    owner = Case
    owners = []
  }
]
align.arrowEnumeratorGenerator = false
align.treeCategory."Defn.Trait" = "class/object/trait/enum"
align.treeCategory."Defn.Object" = "class/object/trait/enum"
align.treeCategory."Defn.Val" = "given/val/var/def"
align.treeCategory."Defn.Enum" = "class/object/trait/enum"
align.treeCategory."Defn.Def" = "given/val/var/def"
align.treeCategory."Defn.GivenAlias" = "given/val/var/def"
align.treeCategory."Defn.Var" = "given/val/var/def"
align.treeCategory."Enumerator.Generator" = for
align.treeCategory."Enumerator.Val" = for
align.treeCategory."Defn.Class" = "class/object/trait/enum"
spaces.beforeContextBoundColon = Never
spaces.afterTripleEquals = false
spaces.inImportCurlyBraces = false
spaces.inInterpolatedStringCurlyBraces = false
spaces.inParentheses = false
spaces.neverAroundInfixTypes = []
spaces.afterKeywordBeforeParen = true
spaces.inByNameTypes = true
spaces.afterSymbolicDefs = false
literals.long = Upper
literals.float = Lower
literals.double = Lower
literals.hexDigits = Lower
literals.hexPrefix = Lower
literals.scientific = Lower
lineEndings = unix
rewrite.rules = []
rewrite.scala3.convertToNewSyntax = false
rewrite.scala3.removeOptionalBraces = no
rewrite.scala3.removeEndMarkerMaxLines = 0
rewrite.scala3.insertEndMarkerMinLines = 0
rewrite.redundantBraces.methodBodies = true
rewrite.redundantBraces.includeUnitMethods = true
rewrite.redundantBraces.maxLines = 100
rewrite.redundantBraces.stringInterpolation = false
rewrite.redundantBraces.parensForOneLineApply = null
rewrite.redundantBraces.generalExpressions = true
rewrite.redundantBraces.ifElseExpressions = false
rewrite.sortModifiers.order = [
  implicit
  final
  sealed
  abstract
  override
  private
  protected
  lazy
  open
  transparent
  inline
  infix
  opaque
]
rewrite.imports.sort = none
rewrite.imports.expand = false
rewrite.imports.contiguousGroups = only
rewrite.imports.groups = []
rewrite.preferCurlyFors.removeTrailingSemicolonsOnly = false
rewrite.neverInfix.includeFilters = [
  "[\w\d_]+"
]
rewrite.neverInfix.excludeFilters = [
  until
  to
  by
  eq
  ne
  "should.*"
  "contain.*"
  "must.*"
  in
  ignore
  be
  taggedAs
  thrownBy
  synchronized
  have
  when
  size
  only
  noneOf
  oneElementOf
  noElementsOf
  atLeastOneElementOf
  atMostOneElementOf
  allElementsOf
  inOrderElementsOf
  theSameElementsAs
]
indentOperator.topLevelOnly = true
indentOperator.include = ".*"
indentOperator.exclude = "^(&&|\|\|)$"
newlines.source = null
newlines.avoidInResultType = false
newlines.beforeTypeBounds = null
newlines.neverBeforeJsNative = false
newlines.sometimesBeforeColonInMethodReturnType = true
newlines.beforeOpenParenDefnSite = null
newlines.beforeOpenParenCallSite = null
newlines.penalizeSingleSelectMultiArgList = true
newlines.alwaysBeforeCurlyBraceLambdaParams = false
newlines.beforeCurlyLambdaParams = never
newlines.topLevelStatementBlankLines = []
newlines.topLevelStatementsMinBreaks = 1
newlines.topLevelStatements = []
newlines.beforeTemplateBodyIfBreakInParentCtors = false
newlines.topLevelBodyIfMinStatements = []
newlines.topLevelBodyMinStatements = 2
newlines.afterCurlyLambdaParams = never
newlines.implicitParamListModifierForce = []
newlines.implicitParamListModifierPrefer = null
newlines.alwaysBeforeElseAfterCurlyIf = false
newlines.forceBeforeMultilineAssign = null
newlines.alwaysBeforeMultilineDef = false
newlines.beforeMultiline = null
newlines.beforeMultilineDef = null
newlines.selectChains = null
newlines.afterInfix = null
newlines.afterInfixBreakOnNested = false
newlines.afterInfixMaxCountPerExprForSome = 10
newlines.afterInfixMaxCountPerFile = 500
newlines.avoidForSimpleOverflow = []
newlines.avoidAfterYield = true
runner.debug = false
runner.eventCallback = "<FormatEvent => Unit>"
runner.parser = Source
runner.optimizer.dequeueOnNewStatements = true
runner.optimizer.escapeInPathologicalCases = true
runner.optimizer.maxVisitsPerToken = 10000
runner.optimizer.maxEscapes = 16
runner.optimizer.maxDepth = 100
runner.optimizer.acceptOptimalAtHints = true
runner.optimizer.disableOptimizationsInsideSensitiveAreas = true
runner.optimizer.pruneSlowStates = true
runner.optimizer.recurseOnBlocks = true
runner.optimizer.forceConfigStyleOnOffset = 150
runner.optimizer.forceConfigStyleMinArgCount = 2
runner.maxStateVisits = 1000000
runner.dialect = default
runner.ignoreWarnings = false
runner.fatalWarnings = false
indentYieldKeyword = true
importSelectors = noBinPack
unindentTopLevelOperators = false
includeCurlyBraceInSelectChains = true
includeNoParensInSelectChains = false
assumeStandardLibraryStripMargin = false
danglingParentheses.callSite = true
danglingParentheses.defnSite = true
danglingParentheses.ctrlSite = true
danglingParentheses.tupleSite = null
danglingParentheses.exclude = []
poorMansTrailingCommasInConfigStyle = false
trailingCommas = never
verticalMultiline.atDefnSite = false
verticalMultiline.arityThreshold = 100
verticalMultiline.newlineBeforeImplicitKW = false
verticalMultiline.newlineAfterImplicitKW = false
verticalMultiline.newlineAfterOpenParen = false
verticalMultiline.excludeDanglingParens = [
  "`class`"
  "`trait`"
]
verticalAlignMultilineOperators = false
onTestFailure = ""
encoding = "UTF-8"
project.git = false
project.includePaths = [
  "glob:**.scala"
  "glob:**.sbt"
  "glob:**.sc"
]
project.excludePaths = []
project.includeFilters = []
project.excludeFilters = []
xmlLiterals.assumeFormatted = false