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Contributing guide

This page documents tips and tricks for contributing to the sourcegraph/lsif-java codebase.

System dependencies

• java: any version should work
• git: any version should work
• gradle: brew install gradle, or see general installation guide.
• mvn: brew install maven, or see general installation guide.

Project structure

These are the main components of the project.

• semanticdb-javac/src/main/java: the Java compiler plugin that creates SemanticDB files.
• tests/minimized: minimized Java source files that reproduce interesting test cases.
• tests/unit: fast running unit tests that are helpful for local edit-and-test workflows.
• tests/snapshots: slow running "snapshot tests" that index a corpus of published Java libraries.
• cli/src/main/scala: implementation of the lsif-java command-line interface.
• build.sbt: the sbt build definition.
• project/plugins.sbt: plugins for the sbt build.

Helpful commands

Command	Where	Description
./sbt	terminal	Start interactive sbt shell with Java 11. Takes a while to load on the first run.
unit/test	sbt	Run fast unit tests.
~unit/test	sbt	Start watch mode to run tests on file save, good for local edit-and-test workflows.
buildTools/test	sbt	Run slow build tool tests (Gradle, Maven).
snapshots/testOnly tests.MinimizedSnapshotSuite	sbt	Runs fast snapshot tests. Indexes a small set of files under tests/minimized.
snapshots/testOnly tests.MinimizedSnapshotSuite -- *InnerClasses*	sbt	Runs only individual tests cases matching the name "InnerClasses".
snapshots/testOnly tests.LibrarySnapshotSuite	sbt	Runs slow snapshot tests. Indexes a corpus of external Java libraries.
snapshots/test	sbt	Runs all snapshot tests.
snapshots/run	sbt	Update snapshot tests. Use this command after you have fixed a bug.
cli/run --cwd DIRECTORY	sbt	Run lsif-java command-line tool against a given Gradle/Maven build.
cd website && yarn install && yarn start	terminal	Start live-reload preview of the website at http://localhost:3000/lsif-java.
docs/mdoc --watch	sbt	Re-generate markdown files in the docs/ directory.
fixAll	sbt	Run Scalafmt, Scalafix and Javafmt on all sources. Run this before opening a PR.

Import the project into IntelliJ

It's recommended to use IntelliJ when editing code in this codebase.

First, install the IntelliJ Community Edition. The community edition is open source and free to use.

Next, install the following IntelliJ plugins:

• IntelliJ Scala plugin.
• Google Java Format

Next, follow these instructions here to configure the Google Java formatter.

Finally, run "File > Project From Existing Sources" to import the sbt build into IntelliJ. Select the "sbt" option if it asks you to choose between sbt/BSP/Bloop.

It's best to run tests from the sbt shell, not from the IntelliJ UI.

Don't use VS Code/Vim/Sublime Text/Emacs

If you want to use completions and precise code navigation, it's not recommended to use other editors than IntelliJ. IntelliJ is the only IDE that properly supports hybrid Java/Scala codebases at the moment, although that may change soon thanks to lsif-java :)

Tests are written in Scala

This codebases uses the Scala library MUnit to write tests because:

• MUnit has built-in assertions that print readable multiline diffs in color.
• MUnit makes it easy to implement snapshot testing, which is a testing technique that's heavily used in this codebase.
• Multiline literal strings in Scala make it easy to write unit tests for source code (which is always multiline). Modern versions of Java support multiline string literals, but they're not supported in Java 8, which is supported by lsif-java.