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A Metals Retrospective (Part 1)

· 9 min read


At the end of 2020 the Metals team sent out a survey to gather input from our users in hopes to get a better picture of who you are, what you want out of Metals, and any other useful feedback you may have wanted to provide. With just under 400 responses we got a ton of great data, some interesting insights, and a nice picture of what is currently hindering users, and what common functionality continually comes up as feature requests. In order to best use this data, and also to share some results, we thought it'd be a good idea to go over some of the sections, address some of the points that came up, and also clear up any misconceptions that may have appeared in the survey results. The idea is for this to be a 2 part series. You can expect the following:

  • Part 1 - Where we discuss some of the initial results and address some common misconceptions and questions.
  • Part 2 - Where we go deeper into the desired features, the biggest pain points, and our plans for this next year.

Editor Support


Surprising no one, VS Code came out on top for editors with the most desire for Metals support. Our VS Code extension has over 100k downloads and it is safe to say that it offers the best support for overall Metals usage. The next most popular of our extensions is probably coc-metals which had just over 20k downloads in 2020. There are certain features that do only work in VS Code mainly due to the robustness of the LSP support and other extra features. Here are a few examples of features that we added this past year that work extremely well with VS Code with no hardly no extra effort on the users part:

  • Debugging support - Early on in 2020 Metals v0.8.0 added debugging support. Now with the click of a button you can run, test, and debug your code right from inside VS Code.
  • Preview renames - in Metals v0.8.1 functionality was added so that you can now preview the changes after triggering a rename for up to 300 files.
  • Analyze stacktrace functionality - As of Metals v0.9.4 Metals gained the ability to take a stack trace and give you a nice view of the entire stack with clickable links to go to that part of your code. This is all found in the very useful web view of VS Code.
  • Show implicits and type decorations - As of Metals v0.9.5 Metals gained the ability to show implicits and type decorations as decorations directly inline of your code.
  • Show implicits conversion and classes - As of Metals v0.9.6 Metals gained the ability to show implicits conversion and classes as decorations directly inline of your code.
  • Navigativing stacktrace while debugging - Also in Metals v0.9.6 the ability to navigate stacktraces during a deubugging sesions was added, which re-used the functionality introduced in v0.9.4 to analyze stacktraces.

Now at this point you may be starting to assume that we heavily favor VS Code and that Metals is geared towards it. We got a few comments related to this throughout the survey. However, I want to make a specific point that since the inception of Metals, the early maintainers did a fantastic job of ensuring that everything would work in clients that offered the necessary LSP support, and also extra features to clients that offered support for the Metals specific LSP extensions that we use. This has remained core for us a we continue to provide new features. Pretty much any new feature that is added is added in a way that can also be utilized for editors that may not have the same level of support as VS Code. Here are a few examples:

  • Debugging support - Metals actually offers deubugging support for any client that can serve as a DAP client. So for example using coc-metals you can also run, test, and debug your code while utilizing vimspector. The same is true for emacs clients that are utilizing lsp-mode.
  • Analyze stacktrace functionality - For clients that don't have a web view, this feature is still supported by producing a file with code lens' in it to allow you to navigate to the relevant parts of the stacktrace.
  • Implicits, type decorations, implicits conversions and classes - VS Code isn't the only extension that actually implements this. There is also metals-sublime that has inline decorations. For other editors that may not support inline decorations, this feature is still re-usable and the information is actually displayed in hover as another section.

So again, while VS Code is an incredible editor, that offers incredible support for the various Metals features, we work hard to ensure that these features are also usable in our other extensions, even if they look a bit different. While there are varying levels of support in the various editor extensions, much of this is due to the those editors being the editors the current maintainers use. We are always open for more help in any of the current editor extensions and this is actually a great way to get involved. We are also open to help you create a new extension to maybe support an editor that is yet to have a Metals-specific extension! Here are links to the various Metals clients:

Will you support IntelliJ?

When asked about what editor people wished had Metals support, here were the results:

Gnome Builder2
Eclipse Theia1

Some of these editors will already actually work with Metals, especially if they support VS Code extensions like Eclipse Theia does. However, one question we often get is: "Will you support IntelliJ?" The simple answer to this question is No, but not for the reason people may think. IntelliJ is a fantastic project that is the most widely used editor in Scala. Metals aims to be a language server for clients that implement LSP. Since IntelliJ has no official support for LSP, we have no intention on adding support for IntelliJ. Many times the target audience is different as well.

Why do people start using Metals

ReasonVery ImportantSomewhat importantNot important
I wanted a lighter alternative to other IDEs.2457427
I could use my favorite editor.2236256
I wanted more accurate compiler errors.2208636
I wanted a fully open source solution.13313869
Metals had features other IDEs didn't56112160

Information and Help with Metals

Over this past year we've done our best to make sure everyone is aware of all the great stuff that is happening in Metals. We have multiple channels of communication open with pretty impressive response times if you ever get stuck. Here are the results about where people go for question about Metals and also where they get their news about Metals.

metals info metals help

Apart from the places that we had listed in the survey, the place mentioned the most for where people hear about Metals related news was Scala Times!

As a reminder, don't ever hesitate to reach out, and if anything is missing in the docs, please lend a helping hand or point it out to us.

I wish Metals had... but it does!

Below are some things that appeared in the survey as wishes, but that Metals already supports, or has added support for since the survey! Hopefully these will help highlight some lesser known features of Metals or serve as a reminder of some of the features we have.

Renaming symbolsAvailable since v0.8.0 and all supported editors support this.
Better info about Ammonite scripts failing.Actually because of this comment, there was some work done to improve the error messages about why Ammonite may not be starting. You can see this here in this pr.
A check telling me if everything is setup correctly.We recently did some work or the Metals Doctor to help you see what issues are going on. You can trigger Doctor by the run-doctor command. It may differ a bit per client. You can see the recent changes made here in this pr.
Seamless install in VimThere are two Metals-specific Vim and Neovim extensions, both which offer an automated install feature. coc-metals and nvim-metals.
Navigating stacktrace feature in emacs.This actually should work, since it just needs code lenses to work for clients that don't have a web view. Part of this is just documentation, so if you're an emacs user, please help us with docs!
Use a specific version of AmmoniteYou can currently do this by setting the version in a comment on the top of a file like illustrated here. Also the next release of Metals will have better support for a fallback version of the compiler that is used for standalone scripts. This will give you more control over what version is used in situations like Ammonite scripts.

What's next?

We want to thank you again for taking the time and filling out our year-end survey. Keep on the lookout for Part 2 of this, and we'll be discussing the biggest pain points and some of the most desired features that we plan to tackle this next year. We'll also do a further look into build server and build tool support finishing off with an update on our current Scala 3 support and the efforts that are going into it.


The Metals team