Vim
Metals works with most LSP clients for Vim, but we recommend using one of the Metals-specific extensions to get the best experience since they offer Metals-specific commands and implement the Metals LSP extensions.
- coc-metals An extension for
coc.nvimIf you're already using other coc.nvim plugins or you are using Vim instead of Neovim, then this is probably the best option for you. Most of the documentation below refers to coc-metals. - nvim-metals A Lua extension for the built-in LSP support in Neovim. Note that this requires at least the 0.5.0 release of Neovim. You can find the full documentation for nvim-metals here.
Requirements#
Java 8, 11, 17 provided by OpenJDK or Oracle. Eclipse OpenJ9 is not
supported, please make sure the JAVA_HOME environment variable
points to a valid Java 8, 11 or 17 installation.
macOS, Linux or Windows. Metals is developed on many operating systems and every PR is tested on Ubuntu, Windows and MacOS.
Scala 2.13, 2.12, 2.11 and Scala 3. Metals supports these Scala versions:
Scala 2.13: 2.13.6, 2.13.5, 2.13.4, 2.13.3, 2.13.2, 2.13.1, 2.13.0
Scala 2.12: 2.12.15, 2.12.14, 2.12.13, 2.12.12, 2.12.11, 2.12.10, 2.12.9, 2.12.8
Scala 2.11: 2.11.12
Scala 3: 3.1.0-RC2, 3.0.2, 3.0.1, 3.0.0
Note that 2.11.x support is deprecated and it will be removed in future releases. It's recommended to upgrade to Scala 2.12 or Scala 2.13
Installing Vim#
The coc.nvim plugin requires either Vim >= 8.1 or Neovim >= 0.3.1. Make sure you have the correct version installed. While it works with both Vim and Neovim, we recommend using Neovim since it provides a smoother experience with some of the features.
Installing Node#
coc.nvim requires Node.js in order to work.
It also uses Yarn to manage
extensions but you could opt-out of it and use vim-plug instead.
For convenience we recommend installing both via your favorite package manager or manually:
Installing coc.nvim#
Once the requirements are satisfied, we can now proceed to install
neoclide/coc.nvim, which provides
Language Server Protocol support to Vim/Nvim to communicate with the Metals
language server.
Assuming vim-plug is used (another
plugin manager like vundle works too), update your ~/.vimrc to include the
following settings.
Run :PlugInstall to install the plugin. If you already have coc.nvim
installed, be sure to update to the latest version with :PlugUpdate.
coc.nvim uses jsonc as a
configuration file format. It's basically json with comment support.
In order to get comment highlighting, please add:
Recommended coc.nvim mappings#
coc.nvim doesn't come with a default key mapping for LSP commands, so you need
to configure it yourself. You can see an example of default mappings
here. Below
you'll find examples of additional coc-metals specific mappings that you'll
also want to ensure you have:
Installing coc-metals#
Once you have coc.nvim installed, you can then install Metals a few different
ways. The easiest is by running:
If you are using the latest stable release of coc.nvim, then this will automatically check for updates each day. However, if you're on the master branch of coc.nvim, this will no longer happen by default. You can read more about this here.
If you'd like to use the latest changes on master, you can also just build from
source by using your vim plugin manager. Here is an example using vim-plug:
Then, issue a :PlugInstall to install the extension, and regularly a
:PlugUpdate to update it and pull in the latest changes.
NOTE* Make sure you don't have the extension installed both ways. So if you have installed it with the built-in extension management of coc.nvim first and are not switching, make sure to uninstall the old version first.
Importing a build#
The first time you open Metals in a new workspace it prompts you to import the build. Click "Import build" to start the installation step.
- "Not now" disables this prompt for 2 minutes.
- "Don't show again" disables this prompt forever, use
rm -rf .metals/to re-enable the prompt. - Use
tail -f .metals/metals.logto watch the build import progress. - Behind the scenes, Metals uses Bloop to import sbt builds, but you don't need Bloop installed on your machine to run this step.
Once the import step completes, compilation starts for your open *.scala
files.
Once the sources have compiled successfully, you can navigate the codebase with goto definition.
Custom sbt launcher#
By default, Metals runs an embedded sbt-launch.jar launcher that respects .sbtopts and .jvmopts.
However, the environment variables SBT_OPTS and JAVA_OPTS are not respected.
Update the metals.sbtScript setting to use a custom sbt script instead of the
default Metals launcher if you need further customizations like reading environment
variables.
Speeding up import#
The "Import build" step can take a long time, especially the first time you run it in a new build. The exact time depends on the complexity of the build and if library dependencies need to be downloaded. For example, this step can take everything from 10 seconds in small cached builds up to 10-15 minutes in large uncached builds.
Consult the Bloop documentation to learn how to speed up build import.
Importing changes#
When you change build.sbt or sources under project/, you will be prompted to
re-import the build.
Configure Java version#
The coc-metals extension uses by default the JAVA_HOME environment variable
(via find-java-home) to locate
the java executable.
If no JAVA_HOME is detected you can then Open Settings by following the
instructions or do it at a later time by using :CocConfig or :CocConfigLocal
which will open up your configuration where you can manually enter your
JAVA_HOME location.
Using latest Metals SNAPSHOT#
Update the "Server Version" setting to try out the latest pending Metals features.
| Version | Published |
|---|---|
| 0.10.7 | 16 Sep 2021 16:28 |
| 0.10.7+17-f589e8b6-SNAPSHOT | 18 Sep 2021 10:35 |
List all workspace compile errors#
To list all compilation errors and warnings in the workspace, run the following command.
Or use the default recommended mapping <space> a.
This is helpful to see compilation errors in different files from your current open buffer.
Worksheets#
Worksheets are a great way to explore an api, try out an idea, or code up an example and quickly see the evaluated expression or result. Behind the scenes worksheets are powered by the great work done in mdoc.
Getting started with Worksheets#
To get started with a worksheet you can either use the metals.new-scala-file
command and select Worksheet or create a file called *.worksheet.sc.
This format is important since this is what tells Metals that it's meant to be
treated as a worksheet and not just a Scala script. Where you create the
script also matters. If you'd like to use classes and values from your
project, you need to make sure the worksheet is created inside of your src
directory. You can still create a worksheet in other places, but you will
only have access to the standard library and your dependencies.
Evaluations#
After saving you'll see the result of the expression differently depending on whether you are using Neovim or Vim. If
using Vim, you will see them appear as comments at the end of
the line. If you're using Nvim you will see this as virtual text.
Keep in mind that if you're using coc-metals with Nvim you'll need
to make sure codeLens.enable is set to true.
You may not see the full result for example if it's too long, so you are also
able to hover on the comment if you're in Vim or expand the virtual text by
using the coc-metals-expand-decoration command. The default for this
is:
Keep in mind that you don't need to wrap your code in an object. In worksheets
everything can be evaluated at the top level.
Using dependencies in worksheets#
You are able to include an external dependency in your worksheet by including it in one of the following two ways.
:: is the same as %% in sbt, which will append the current Scala binary version
to the artifact name.
You can also import scalac options in a special $scalac import like below:
Tree View Protocol#
coc-metals has a built-in implementation of the Tree View
Protocol.
If you have the recommended mappings copied, you'll notice
that in the bottom you'll have some TVP related settings. You can start by
opening the TVP panel by using the default <space> t. Once open, you'll see
there are three parts to the panel. The first being the MetalsCompile window
where you can see ongoing compilations, the second is the MetalsPackages
window where you are able to see a tree view of all your packages, and finally
the metalsBuild window where you have build related commands.
You are able to trigger the commands while being on top of the option you are
attempting to trigger and pressing r. You can change this default in the
settings. You can find all the relevant TVP settings below in the Available
Configuration Options.
Tree View Protocol configuration options#
| Configuration Option | Description |
|---|---|
metals.treeviews.toggleNode | Expand / Collapse tree node (default <CR>) |
metals.treeviews.initialWidth | Initial Tree Views panels (default 40) |
metals.treeviews.initialViews | Initial views that the Tree View Panel displays. Don't mess with this unless you know what you're doing. |
metals.treeviews.gotoLastChild | Go to the last child Node (default J) |
metals.treeviews.gotoParentNode | Go to parent Node (default p) |
metals.treeviews.gotoFirstChild | Go to first child Node (default K) |
metals.treeviews.executeCommand | Execute command for node (default r) |
metals.treeviews.gotoPrevSibling | Go to prev sibling (default <C-k>) |
metals.treeviews.gotoNextSibling | Go to next sibling (default <C-j>) |
metals.treeviews.forceChildrenReload | Force the reloading of the children of this node. May be useful when the wrong result is cached and tree contains invalid data. (default f) |
metals.treeviews.executeCommandAndOpenTab | Execute command and open node under cursor in tab (if node is class, trait and so on) (default t) |
metals.treeviews.executeCommandAndOpenSplit | Execute command and open node under cursor in horizontal split (if node is class, trait and so on) (default s) |
metals.treeviews.executeCommandAndOpenVSplit | Execute command and open node under cursor in vertical split (if node is class, trait and so on) (default v) |
Goto Super Method#
Depending on whether you're using Vim or Neovim, you'll have a slightly
different behavior with this feature. If you're using Neovim, you'll want to
ensure that you have codeLens.enable set to true in your :CocConfig since
you'll be able to quickly see via code lenses which members are overridden.
Then, you'll be able to simply trigger a code lens action on the line of the
member that is overridden. The default mapping for this is <leader> cl.
If you're using Vim, you'll still have access to this functionality, but you'll
have to infer which members are overridden and utilize the
metals.go-to-super-method command.
There is also a metals.super-method-hierarchy command which will show you the
entire hierarchy of the overridden method.
If you don't utilize this feature you can disable it by setting
metals.superMethodLensesEnabled to false.
Run doctor#
To troubleshoot problems with your build workspace, open your coc commands by either
using :CocCommand or the recommend mapping <space> c. This will open your command
window allowing you to search for metals.doctor-run command.
This command opens an embedded doctor in your preview window. If you're not familiar with
having multiple windows, you can use <C-w> + w to jump into it.
Other Available Commands#
You can see a full list of the Metals server commands here.
Show document symbols#
Run :CocList outline to show a symbol outline for the current file or use the
default mapping <space> o.
Available Configuration Options#
The following configuration options are currently available. The easiest way to
set these configurations is to enter :CocConfig or :CocLocalConfig to set
your global or local configuration settings respectively.
If you'd like to get autocompletion help for the configuration values you can
install coc-json.
Java Home directory#
The Java Home directory used for indexing JDK sources and locating the java binary.
Default: JAVA_HOME environment variable with fallback to user.home system property.
Example:
sbt script#
Optional absolute path to an sbt executable to use for running sbt bloopInstall.
By default, Metals uses java -jar sbt-launch.jar with an embedded launcher while respecting
.jvmopts and .sbtopts. Update this setting if your sbt script requires more customizations
like using environment variables.
Default: empty string "".
Example:
Gradle script#
Optional absolute path to a gradle executable to use for running gradle bloopInstall.
By default, Metals uses gradlew with 5.3.1 gradle version. Update this setting if your gradle script requires more customizations
like using environment variables.
Default: empty string "".
Example:
Maven script#
Optional absolute path to a maven executable to use for generating bloop config.
By default, Metals uses mvnw maven wrapper with 3.6.1 maven version. Update this setting if your maven script requires more customizations
Default: empty string "".
Example:
Mill script#
Optional absolute path to a mill executable to use for running mill mill.contrib.Bloop/install.
By default, Metals uses mill wrapper script with 0.5.0 mill version. Update this setting if your mill script requires more customizations
like using environment variables.
Default: empty string "".
Example:
Scalafmt config path#
Optional custom path to the .scalafmt.conf file.
Should be an absolute path and use forward slashes / for file separators (even on Windows).
Default: empty string "".
Example:
Scalafix config path#
Optional custom path to the .scalafix.conf file.
Should be an absolute path and use forward slashes / for file separators (even on Windows).
Default: empty string "".
Example:
Ammonite JVM Properties#
Optional list of JVM properties to pass along to the Ammonite server.
Each property needs to be a separate item.\n\nExample: -Xmx1G or -Xms100M"
Default: [].
Example:
Excluded Packages#
Packages that will be excluded from completions, imports, and symbol searches.
Note that this is in addition to some default packages that are already excluded. The default excluded packages are listed below:
If there is a need to remove one of the defaults, you are able to do so by including the
package in your list and prepending -- to it.
Example:
Default: [].
Example:
Don't generate Bloop plugin file for sbt#
If true, Metals will not generate metals.sbt files under the assumption that sbt-bloop is already manually installed in the sbt build. Build import will fail with a 'not valid command bloopInstall' error in case Bloop is not manually installed in the build when using this option.
Default: false
Example:
Version of Bloop#
This version will be used for the Bloop build tool plugin, for any supported build tool, while importing in Metals as well as for running the embedded server
Default: 1.4.9
Example:
Should display lenses with links to super methods#
Super method lenses are visible above methods definition that override another methods. Clicking on a lens jumps to super method definition. Disabled lenses are not calculated for opened documents which might speed up document processing.
Default: false
Example:
Should display type annotations for inferred types#
When this option is enabled, each method that can have inferred types has them displayed either as additional decorations if they are supported by the editor or shown in the hover.
Default: false
Example:
Should display implicit parameter at usage sites#
When this option is enabled, each method that has implicit arguments has them displayed either as additional decorations if they are supported by the editor or shown in the hover.
Default: false
Example:
Should display implicit conversion at usage sites#
When this option is enabled, each place where an implicit method or class is used has it displayed either as additional decorations if they are supported by the editor or shown in the hover.
Default: false
Example:
Should try adjust indentation on range formatting.#
When this option is enabled, when user pastes any snippet into a Scala file, Metals will try to adjust the indentation to that of the current cursor.
Default: false
Example:
Remote language server#
A URL pointing to an endpoint that implements a remote language server.
See https://scalameta.org/metals/docs/contributors/remote-language-server.html for documentation on remote language servers.
Default: empty string "".
Example:
Default fallback Scala version#
The Scala compiler version that is used as the default or fallback in case a file doesn't belong to any build target or the specified Scala version isn't supported by Metals. This applies to standalone Scala files, worksheets, and Ammonite scripts.
Default: 2.12.15
Example:
Create new project from template#
It is possible using Metals to easily setup a new project using the exiting giter8 templates.
This is an equivalent to the sbt new command, which uses the same mechanism.
There is a great number of templates already available and it should be easy to find something for yourself.
To start the setup you can use the new-scala-project command, which works as following:
- Choose the template and then:
- Use the proposed templates.
- Choose "Discover more" and then choose from the list downloaded from the Giter8 wiki page.
- Input a custom Github repository following the
organization/reposchema.
- Navigate to the parent directory that you want to create your new project in.
- Choose the name or accept the default one.
If you feel like a template should be included in the default displayed ones do not hesitate to create a PR or file an issue.
Enable on type formatting for multiline string formatting#
To properly support some of the multiline string options like adding | in
the multiline string, we are using the onTypeFormatting method. To enable the
functionality you need to enable coc.preferences.formatOnType setting.
Close buffer without exiting#
To close a buffer and return to the previous buffer, run the following command.
This command is helpful when navigating in library dependency sources in the .metals/readonly directory.
Shut down the language server#
The Metals server is shutdown when you exit vim as usual.
Statusline integration#
It's recommended to use a statusline integration with coc-metals in order to
allow messages to be displayed in your status line rather than as a message.
This will allow for a better experience as you can continue to get status
information while entering a command or responding to a prompt. However, we
realize that not everyone by default will have this setup, and since the user
needs to see messages about the status of their build, the following is
defaulted to false.
Again, it's recommended to make this active, and use a statusline plugin, or
manually add the coc status information into your statusline. coc.nvim has
multiple ways to integrate with various statusline plugins. You can find
instructions for each of them located
here. If
you're unsure of what to use,
vim-airline is a great minimal
choice that will work out of the box.
With vim-airline you'll notice two noteworthy things. The first will be that you'll have diagnostic information on the far right of your screen.
You'll also have metals status information in your status bar.
Without a statusline integration, you'll get messages like you see below.
If you don't use a statusline plugin, but would still like to see this
information, the easiest way is to make sure you have the following in your
.vimrc.
Formatting on save#
Add the following configuration to :CocConfig if you'd like to have :w format using Metals and
Scalafmt.
This step cleans up resources that are used by the server.
Files and Directories to include in your Gitignore#
The Metals server places logs and other files in the .metals directory. The
Bloop compile server places logs and compilation artifacts in the .bloop
directory. The Bloop plugin that generates Bloop configuration is added in the
metals.sbt file, which is added at project/metals.sbt as well as further
project directories depending on how deep *.sbt files need to be supported.
To support each *.sbt file Metals needs to create an additional file at
./project/project/metals.sbt relative to the sbt file.
Working with Ammonite scripts will place compiled scripts into the .ammonite directory.
It's recommended to exclude these directories and files
from version control systems like git.
Using an alternative LSP Client#
While we recommend using the coc-metals extension with coc.nvim, or
nvim-metals with Neovim, Metals will work with these alternative LSP clients.
Keep in mind that they have varying levels of LSP support, and you need to
bootstrap Metals yourself.
vim-lsc: simple installation and written in Vimscript.LanguageClient-neovim: client written in Rust.vim-lsp: simple installation and written in Vimscript.
Generating metals binary#
If you only want to use the latest stable version of Metals, the easiest way to
install Metals is using coursier. Once installed you
can simply do a cs install metals to install the latest stable version of
Metals. You can then also do a cs update metals to update it.
If you'd like to bootstrap your own Metals for a specific version, you're also able to do so like this:
Next, build a metals-vim binary for the latest Metals release using the
Coursier command-line interface.
| Version | Published | Resolver |
|---|---|---|
| 0.10.7 | 16 Sep 2021 16:28 | -r sonatype:releases |
| 0.10.7+17-f589e8b6-SNAPSHOT | 18 Sep 2021 10:35 | -r sonatype:snapshots |
Make sure the generated metals-vim binary is available on your $PATH.
You can check version of your binary by executing metals-vim -version.
Configure the system properties -Dhttps.proxyHost=… -Dhttps.proxyPort=…
if you are behind an HTTP proxy.
The -Dmetals.client=vim-lsc flag is there just as a helper to match your
potential client. So make sure it matches your client name. This line isn't
mandatory though as your client can fully be configured via
InitializationOptions, which should be easily configurable by your client. You
can read more about his
here.