Metals extension for Visual Studio Code

The following table shows the status of various features.

Feature	Status	Notes
Import build	✅	Works with sbt, Gradle, Maven, Mill and Bloop.
Compile errors	✅	Syntax errors as you type and type errors on file save.
Completions	✅
Hover (type at point)	✅
Goto definition	✅	Works for project sources and Java/Scala library dependencies.
Document symbols	✅
Formatting	✅	Uses Scalafmt.
Find references	✅
Find implementations	✅
Workspace symbol	✅	Searches workspace sources and library dependencies. All-lowercase queries are case-insensitive.
Highlight	✅
Folding	✅
Rename symbol	✅
Run/Debug	✅

Requirements

Java 8 or 11 provided by OpenJDK or Oracle. Eclipse OpenJ9 is not supported, please make sure the JAVA_HOME environment variable points to a valid Java 8 or 11 installation.

macOS, Linux or Windows. Metals is developed on macOS and every PR is tested on Ubuntu+Windows.

Scala 2.13, 2.12 and 2.11. Metals supports these Scala versions 2.13.0, 2.13.1, 2.12.10, 2.12.8, 2.12.9 and 2.11.12. 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

Installation

Install the Metals extension from the Marketplace.

Make sure to disable the extensions Scala Language Server and Scala (sbt) if they are installed. The Dotty Language Server does not need to be disabled because the Metals and Dotty extensions don't conflict with each other.

Next, open a directory containing a build.sbt file. The extension activates when a *.scala or *.sbt file is opened.

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.log to 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 "Sbt Script" 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 your build.sbt or sources under project/, you will be prompted to re-import the build.

Manually trigger build import

To manually trigger a build import, execute the "Import build" command through the command palette (Cmd + Shift + P).

Run doctor

Execute the "Run Doctor" through the command palette to troubleshoot potential configuration problems in your workspace.

Configure Java version

The VS Code plugin uses by default the JAVA_HOME environment variable (via find-java-home) to locate the java executable. To override the default Java home location, update the "Java Home" variable in the settings menu.

If this setting is defined, the VS Code plugin uses the custom path instead of the JAVA_HOME environment variable.

macOS

To globally configure $JAVA_HOME for all GUI applications, see this Stackoverflow answer.

If you prefer to manually configure Java home through VS Code, run the following command to copy the Java 8 home path.

/usr/libexec/java_home -v 1.8 | pbcopy

Custom artifact repositories (Maven or Ivy resolvers)

Use the 'Custom Repositories' setting for the Metals VS Code extension to tell Coursier to try to download Metals artifacts from your private artifact repository.

Use .jvmopts to set sbt options (https://www.scala-sbt.org/1.0/docs/Proxy-Repositories.html) for sbt bloopInstall which resolves library dependencies. You can also provide a custom sbt script (see 'Custom sbt launcher').

HTTP proxy

Metals uses Coursier to download artifacts from Maven Central. To use Metals behind an HTTP proxy, configure the system properties -Dhttps.proxyHost=… -Dhttps.proxyPort=… in one of the following locations:

.jvmopts file in the workspace directory.
JAVA_OPTS environment variable, make sure to start code from your terminal when using this option since environment variables don't always propagate correctly when opening VS Code as a GUI application outside a terminal.
"Server Properties" setting for the Metals VS Code extension, which can be configured per-workspace or per-user.

Using latest Metals SNAPSHOT

Update the "Server Version" setting to try out the latest pending Metals features.

See https://scalameta.org/metals/docs/editors/vscode.html#using-latest-metals-snapshot to find the latest SNAPSHOT version.

Run the "Reload Window" command after updating the setting for the new version to take effect.

Gitignore `project/metals.sbt` `.metals/` and `.bloop/`

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. Bloop plugin that generates Bloop configuration is added in the project/metals.sbt file. It's recommended to ignore these directories and file from version control systems like git.

# ~/.gitignore
.metals/
.bloop/
project/metals.sbt

Show document symbols

Run the "Explorer: Focus on Outline View" command to open the symbol outline for the current file in the sidebar.

Run the "Open Symbol in File" command to search for a symbol in the current file without opening the sidebar.

As you type, the symbol outline is also visible at the top of the file.

Enable on type formatting for multiline string formatting

To properly support adding | in multiline strings we are using the onTypeFormatting method. To enable the functionality you need to enable onTypeFormatting inside Visual Studio Code.

This needs to be done in settings by checking Editor: Format On Type:

Enable formatting on paste for multiline strings

Whenever text is paste into a multiline string with | it will be properly formatted by Metals:

To enable this feature you need to enable formatting on paste in Visual Studio Code by checking Editor: Format On PAste:

Coming from IntelliJ

Install the IntelliJ IDEA Keybindings extension to use default IntelliJ shortcuts with VS Code.

IntelliJ	VS Code
Go to class	Go to symbol in workspace
Parameter info	Trigger parameter hints
Basic completion	Trigger suggest
Type info	Show hover
Expand	Fold
Extend Selection	Expand selection

alekseiAlefirov / metals-vscode

Metals extension for Visual Studio Code

Requirements

Installation