Add SemanticDB support - cont.

[crt-31]

Description

Adds Semanticdb output capability

This PR extends the PR drafts #1467 and #1329, and as such builds on the great work so far by @olafurpg and @ricochet1k, and @aishfenton. In particular, this PR moves the semanticddb handling into a phase instead of the scalacworker, as well as some other improvements.

Features

• Semanticdb output can be enabled on a toolchain by settting scala_toolchain.enable_semanticdb. Default is False for performance reasons (generating semanticdb adds considerable overhead to a build).
  • Works with setup_scala_toolchain() too
• Scala 2 & 3 is supported.
• By default, Semanticdb files are output to a semanticdb folder. Also supports bundling of semanticdb files inside the output jar if desired.
• 3rd party tooling can obtain Semanticdb information (i.e. directory containing the semanticdb files) through a SemanticdbInfo Provider (i.e. using an aspect). Example included.

Motivation

Semanticdb is needed by many tools and IDEs (i.e. Metals, Scalafix, etc). This will hopefully support integration of more tools with rules_scala and help accelerate its usage in the community.

[johnynek]

I hope we can merge this soon. It's been a long-missing capability.

[liucijus]

@crt-31 sorry for the delay with a review. I'm currently on my PTO, I'll do a proper review after two weeks if this can wait.

I quickly went over changes - implementation looks good. I want to do some testing and a bit of naming nit-picking when I'll be back for a proper review.

[crt-31]

@liucijus, are you able to rerun the CI tests for this PR? It seems to have hung for some reason.

[liucijus]

@liucijus, are you able to rerun the CI tests for this PR? It seems to have hung for some reason.

Unfortunately, no, but let's ignore it as it's flaky