scala 3 support?

[name-snrl]

When I try to run mezel with the scala 3 example, it complains about the lack of semanticdb:

### //src:lib
  - target type: Scala 3.1.0
  - goto functionality: metalsDecode:file%3A%2F%2F%2Ftest%2F%2F%2Fsrc%3Alib.metals-buildtarget
  - compilation: ✅ 
  - diagnostics: ✅ 
  - interactive: ✅ 
  - semanticdb: ❌
  - debugging: ❌
  - java: ⚠️ 
  - recommendation: Run 'Import build' to enable code navigation.

I haven't read the code much, but it looks like it uses scala 2 options to generate semanticdb, I guess this is a problem for me?

https://github.com/ValdemarGr/mezel/blob/89ab108cdff0773458b647dea884521b0627119e/src/main/scala/mezel/BSPServer.scala#L523-L527

[ValdemarGr]

Thanks for the report. I'll look into it.

[ValdemarGr]

I got semanticdb working for Scala 3 by adding the correct flags. You can take a look at the ./example project

### //example/src/main/scala/example:example
  - target type: Scala 3.3.0
  - goto functionality: metalsDecode:file%3A%2F%2F%2Fmezel%2F%2F%2Fexample%2Fsrc%2Fmain%2Fscala%2Fexample%3Aexample.metals-buildtarget
  - compilation: ✅ 
  - diagnostics: ✅ 
  - interactive: ✅ 
  - semanticdb: ✅ 
  - debugging: ❌
  - java: ⚠️ 

However I noticed that rules_scala don't seem to generate diagnosticsproto files for Scala 3, so I cannot provide editor diagnostics (errors and warnings).

It is marked as a output of the Scalac action, and is in fact generated if there are no errors, but if errors occur in a target the diagnostics file is not emitted, if warnings but no errors occur the file will be present but it will be empty.

bazel aquery 'mnemonic("Scalac", //example/src/main/scala/example)' | grep "Outputs:.*diagnostics.*"
#   Outputs: [bazel-out/k8-fastbuild/bin/example/src/main/scala/example/_semanticdb/example/META-INF/semanticdb/example/src/main/scala/example/Main.scala.semanticdb, bazel-out/k8-fastbuild/bin/example/src/main/scala/example/example.diagnosticsproto, bazel-out/k8-fastbuild/bin/example /src/main/scala/example/example.jar, bazel-out/k8-fastbuild/bin/example/src/main/scala/example/example.sdeps, bazel-out/k8-fastbuild/bin/example/src/main/scala/example/example.statsfile]

I think this might be a bug (or missing feature) that needs to be addressed in rules_scala, I'll look into it. For now, I'll publish a version that won't expect diagnosticsproto to exist on the filesystem, so navigation and type hits should work for Scala 3.

[ValdemarGr]

After some quick investigation it seems that Scala 3 diagnostics are a missing feature.

• https://github.com/bazelbuild/rules_scala/blob/master/src/java/io/bazel/rulesscala/scalac/reporter/PlaceholderForEmptyScala3Lib.java
• https://github.com/scoquelin/rules_scala/blob/feebb1d117d115b753a3df364a5bca49a5dfac64/src/java/io/bazel/rulesscala/scalac/reporter/BUILD

[name-snrl]

by adding the correct flags

Thanks for the tests, glad to hear it's working. I haven't had a chance to test it since yesterday.

rules_scala don't seem to generate diagnosticsproto

This is not a problem for us, because we are using our own forked https://github.com/higherkindness/rules_scala rules and diagnosticproto is not yet implemented.

[name-snrl]

at the ./example project

At first I tried the example, but could not succeed. Then I thought "ok, I'll try with scala 2, from the beginning" and created this repo with two branches, bazel and sbt versions.

https://github.com/name-snrl/mezel_example

The main feature I expect is code navigation, but goto-definition only works on the sbt branch. For example, if I try to navigate to IOApp, it doesn't work on the bazel branch. Any ideas?

Cold start logs, after something like:

bazel clean --expunge &&
    pkill java &&
    rm -rf .metals/ .bloop/ project/ target/ ~/.cache/{bazel/,coursier/,bloop/,bazelisk/} &&
    git restore .

bazel.log sbt.log

[ValdemarGr]

The aspect does not catch rules of kind scala_binary. I'll add that to the aspect c06d9d88568f4ad09c4fca072b57839374f83720 fixes it.

If you use scala_library it should also work.

load("@io_bazel_rules_scala//scala:scala.bzl", "scala_library")

scala_library(
    name = "example",
    srcs = ["Main.scala"],
    # main_class = "example.Main",
    visibility = ["//visibility:public"],
    deps = [
      "@maven//:org_typelevel_cats_effect_2_13",
    ],
)

[name-snrl]

If you use scala_library it should also work.

Hm... But as I see, goto definition still doesn't work.

I thought the main problem with bazel-bsp was semanticdb, that after providing semanticdb to metals, all code navigation like goto definition would start working. Am I still doing something wrong? Or do we need to add something else to make it work?

p.s. I have autocomplete like in your screenshot

[ValdemarGr]

Sorry for the inconvenience, the issue you hit was twofold:

• You must fetch sources when fetching external jar dependencies such that there are sources to jump to, this is documented now.
• After doing so I found a bug in the path construction for external sources which is now fixed. I need to publish a new version of the binary (jar) have published a new version that fixes this issue.

https://github.com/ValdemarGr/mezel/assets/22582195/ceaa1256-8bc8-45d6-9f39-6404878ba8b0