Setting up your IDE

You can use either Metals with your favorite editor or IntelliJ IDEA for Scala to work on the Scala 3 codebase. There are however a few additional considerations to take into account.

Bootstrapping Projects

The sbt build for dotty implements bootstrapping within the same build, so each component has two projects:

sbt:scala3> projects
...
[info] 	   scala3-compiler
[info] 	   scala3-compiler-bootstrapped
...

These duplicated projects can be confusing and cause issues in IDEs, so it's import to import the project in a specific way depending on your editor.

Metals

When using Metals, the -bootstrapped projects are not exported by default. Normally this is fine, but if you're working on certain modules like scaladoc you'll actually want these modules exported. In order to achieve this you'll want to make sure you do two things:

1. You'll want to find and change the following above commonBootstrappedSettings which is found in the Build.scala file.

-    val enableBspAllProjects = false,
+    val enableBspAllProjects = true,

2. Run in sbt shell sbt> scala3-bootstrapped/compile and then sbt> scala3-bootstrapped/publishLocalBin to get the required presentation compiler jars.

   If any step fails due to random errors, try removing ./out/ directory and running sbt> clean

   This step has to be repeated every time compiler version has been bumped.

By default Metals uses Bloop build server, however you can also use sbt directly. You can achieve this with the Metals: Switch Build Server command and then choosing sbt. In VSCode, this looks like this:

IntelliJ

In IntelliJ IDEA, we recommend importing the dotty codebase through BSP, then the -bootstrapped projects are not exported.