Metals extension for Visual Studio Code
Metals is still in early development so you may run into rough edges. The following table shows the status of various features.
|Import build||Works with sbt and Bloop.|
|Compile errors||Triggered on file save.|
|Goto definition||Works for both project sources and Java/Scala library dependencies.|
|Workspace symbol||Works for both project sources and Java/Scala library dependencies. All-lowercase queries are case-insensitive searches.|
Java 8. Metals does not work with Java 11 yet so make sure the JAVA_HOME environment variable points to Java 8.
macOS, Linux or Windows. Metals is developed on macOS and every PR is tested on Ubuntu+Windows.
Scala 2.12 and 2.11. Metals works only with Scala versions 2.12.8, 2.12.7, 2.12.6, 2.12.5, 2.12.4, 2.11.12, 2.11.11, 2.11.10 and 2.11.9. Note that 2.10.x and 2.13.0-M5 are not supported.
Install the Metals extension from the Marketplace, search for "Metals".
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
*.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.
- 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
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
.jvmopts. However, the environment variables
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
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.
When you change
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).
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. Metals only works with Java 8 so this executable cannot point
to another version such as Java 11.
To override the default Java home location, update the "Java Home" variable to in the settings menu.
If this setting is defined, the VS Code plugin uses the custom path instead of
JAVA_HOME environment variable.
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
The Metals server places logs and other files in the
.metals/ directory. The
Bloop compile server places logs and compilation artifacts in the
directory. It's recommended to ignore these directories from version control
systems like git.
# ~/.gitignore .metals/ .bloop/
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.