Drop support for indexing Scala code (#883)

- Remove SbtBuildTool, MillBuildTool, ScalaCompilerClassLoader, ScalaVersion
- Remove all Scala minimized fixtures and snapshot outputs (ujson, minimized-scala)
- Remove sbt and mill from auto-detected build tools
- Remove Scala/SBT/Mill versions and build info keys from build.sbt
- Remove Scala presentation compiler code from TestCompiler
- Remove Scala plugin support from semanticdb-gradle-plugin
- Drop -build-tool:mill flag from semanticdb-javac
- Remove Scala-specific synthetic-symbol handling from scip-semanticdb
- Update docs and README to reflect Java/Kotlin-only support
- Remove mill from flake.nix dev shell

Author: jupblb

CONTRIBUTING.md

@@ -85,15 +85,6 @@ sbt/BSP/Bloop.
 
 It's best to run tests from the sbt shell, not from the IntelliJ UI.
 
-## Importing the project with Metals
-
-While the cross-language support won't be as rich as it is in IntelliJ,
-[Metals](https://scalameta.org/metals/) does offer rich language support for
-Scala and basic Java navigation support (thanks to scip-java!). When using
-Metals and your editor of choice it's recommended to use sbt as your build
-server. This isn't the default with Metals, so you'll want to use the `Metals:
-Switch build server` command and choose `sbt`.
-
 ## Tests are written in Scala
 
 This codebases uses the Scala library [MUnit](https://scalameta.org/munit/) to

README.md

@@ -1,4 +1,4 @@
-# Java, Scala, and Kotlin indexer for [SCIP](https://github.com/sourcegraph/scip) ![](https://img.shields.io/badge/status-development-green?style=flat)
+# Java and Kotlin indexer for [SCIP](https://github.com/sourcegraph/scip) ![](https://img.shields.io/badge/status-development-green?style=flat)
 
 | Documentation        | Link                                                                   |
 | -------------------- | ---------------------------------------------------------------------- |

build.sbt

@@ -14,12 +14,8 @@ lazy val V =
     val moped = "0.2.0"
     val gradle = "7.0"
     val scala213 = "2.13.13"
-    val scala3 = "3.3.3"
-    val metals = "1.2.2"
     val scalameta = "4.9.3"
     val requests = "0.8.0"
-    val minimalMillVersion = "0.10.0"
-    val millScipVersion = "0.3.6"
     val kotlinVersion = "2.2.0"
     val kotest = "4.6.3"
     val kctfork = "0.7.1"
@@ -117,20 +113,8 @@ lazy val gradlePlugin = project
         sbtVersion,
         scalaVersion,
         "javacModuleOptions" -> javacModuleOptions,
-        "semanticdbScalacVersions" ->
-          com
-            .sourcegraph
-            .sbtsourcegraph
-            .Versions
-            .cachedSemanticdbVersionsByScalaVersion,
-        "sbtSourcegraphVersion" ->
-          com.sourcegraph.sbtsourcegraph.BuildInfo.version,
         "semanticdbVersion" -> V.scalameta,
-        "mtagsVersion" -> V.metals,
-        "scala213" -> V.scala213,
-        "scala3" -> V.scala3,
-        "minimalMillVersion" -> V.minimalMillVersion,
-        "millScipVersion" -> V.millScipVersion
+        "scala213" -> V.scala213
       )
   )
   .enablePlugins(BuildInfoPlugin)
@@ -241,31 +225,17 @@ lazy val cli = project
         sbtVersion,
         scalaVersion,
         "javacModuleOptions" -> javacModuleOptions,
-        "semanticdbScalacVersions" ->
-          com
-            .sourcegraph
-            .sbtsourcegraph
-            .Versions
-            .cachedSemanticdbVersionsByScalaVersion,
-        "sbtSourcegraphVersion" ->
-          com.sourcegraph.sbtsourcegraph.BuildInfo.version,
         "semanticdbVersion" -> V.scalameta,
-        "mtagsVersion" -> V.metals,
-        "scala213" -> V.scala213,
-        "scala3" -> V.scala3,
-        "minimalMillVersion" -> V.minimalMillVersion,
-        "millScipVersion" -> V.millScipVersion
+        "scala213" -> V.scala213
       ),
     buildInfoPackage := "com.sourcegraph.scip_java",
     libraryDependencies ++=
       List(
         "io.get-coursier" %% "coursier" % V.coursier,
         "io.get-coursier" %% "coursier-jvm" % V.coursier,
-        "org.scalameta" % "mtags-interfaces" % V.metals,
         "org.scala-lang.modules" %% "scala-xml" % V.scalaXml,
         "com.lihaoyi" %% "requests" % V.requests,
         "org.scalameta" %% "moped" % V.moped,
-        "org.scalameta" %% "ascii-graphs" % "0.1.2",
         "org.jetbrains.kotlin" % "kotlin-compiler-embeddable" % V.kotlinVersion,
         "org.jetbrains.kotlin" % "kotlin-scripting-common" % V.kotlinVersion,
         "org.jetbrains.kotlin" % "kotlin-scripting-jvm" % V.kotlinVersion,
@@ -627,15 +597,6 @@ lazy val minimized21 = project
   .dependsOn(agent, javacPlugin)
   .disablePlugins(JavaFormatterPlugin)
 
-lazy val minimizedScala = project
-  .in(file("tests/minimized-scala"))
-  .settings(
-    (publish / skip) := true,
-    semanticdbOptions ++=
-      List("-P:semanticdb:text:on", "-P:semanticdb:synthetics:on")
-  )
-  .dependsOn(minimized)
-
 lazy val unit = project
   .in(file("tests/unit"))
   .settings(
@@ -649,11 +610,7 @@ lazy val unit = project
         "sourceroot" -> (ThisBuild / baseDirectory).value,
         "minimizedJavaSourceDirectory" -> minimizedSourceDirectory,
         "minimizedJavaTargetroot" ->
-          (minimized / Compile / semanticdbTargetRoot).value,
-        "minimizedScalaSourceDirectory" ->
-          (minimizedScala / Compile / sourceDirectory).value / "scala",
-        "minimizedScalaTargetroot" ->
-          (minimizedScala / Compile / semanticdbTargetRoot).value
+          (minimized / Compile / semanticdbTargetRoot).value
       ),
     buildInfoPackage := "tests"
   )
@@ -694,7 +651,7 @@ lazy val snapshots = project
       ),
     buildInfoPackage := "tests.snapshots"
   )
-  .dependsOn(minimizedScala, unit)
+  .dependsOn(unit)
   .enablePlugins(BuildInfoPlugin)
 
 lazy val bench = project
@@ -730,7 +687,6 @@ val testSettings = List(
   libraryDependencies ++=
     List(
       "org.scalameta" %% "munit" % "0.7.29",
-      "org.scalameta" %% "mtags" % V.metals cross CrossVersion.full,
       "org.scalameta" %% "moped-testkit" % V.moped,
       "org.scalameta" %% "scalameta" % V.scalameta,
       "io.get-coursier" %% "coursier" % V.coursier,

docs/design.md

@@ -28,8 +28,8 @@ There are several benefits to implementing scip-java as a compiler plugin:
 ### Why SemanticDB?
 
 SemanticDB is Protobuf schema for information about symbols and types in Java
-programs, Scala programs and other languages. There are several benefits to
-using SemanticDB as an intermediary representation for SCIP:
+programs and other languages. There are several benefits to using SemanticDB as
+an intermediary representation for SCIP:
 
 - **Simplicity**: It's easy to translate a single Java source file into a single
   SemanticDB file inside a compiler plugin. It's more complicated to produce
@@ -39,14 +39,9 @@ using SemanticDB as an intermediary representation for SCIP:
 - **Performance**: SemanticDB is fast to write and read. Each compilation unit
   can be processed independently to keep memory usage low. The final conversion
   from SemanticDB to SCIP can be safely parallelized.
-- **Cross-language**: SemanticDB has a
-  [spec](https://scalameta.org/docs/semanticdb/specification.html) for Java and
-  Scala enabling cross-language navigation in hybrid Java/Scala codebases.
 - **Cross-repository**: Compiler plugins have access to both source code and the
   classpath (compiled bytecode of upstream dependencies). SemanticDB has been
   designed so that it's also possible to generate spec-compliant symbols from
   the classpath alone (no source code) and from the syntax tree of an individual
-  source file (no classpath). This flexibility allows the
-  [Metals](https://scalameta.org/metals/) language server to index codebases
-  from a variety of different inputs, and will be helpful for scip-java in the
-  future to unblock cross-repository navigation.
+  source file (no classpath). This flexibility will be helpful for scip-java in
+  the future to unblock cross-repository navigation.

docs/getting-started.md

@@ -5,7 +5,7 @@ title: Getting started
 
 By following the instructions on this page, you should be able to generate a
 [SCIP](https://github.com/sourcegraph/scip) index of your Java codebase using
-Gradle, Maven, sbt, or Bazel. See
+Gradle, Maven, or Bazel. See
 [Supported build tools](#supported-build-tools) for an overview of other build
 tools that we're planning to support in the future.
 
@@ -136,16 +136,9 @@ If you're using Maven.
 </dependency>
 ```
 
-If you're using sbt.
-
-```scala
-scalaVersion := "@SCALA_VERSION@" // Only Scala 2.13 is supported.
-libraryDependencies += "com.sourcegraph" %% "scip-java" % "@STABLE_VERSION@"
-```
-
 ## Run `scip-java index`
 
-> The `index` command is only supported for Gradle, Maven and sbt. See
+> The `index` command is only supported for Gradle and Maven. See
 > [Supported build tools](#supported-build-tools) for more details about other
 > build tools.
 
@@ -156,18 +149,16 @@ This command should automatically infer the structure of your codebase and
 configure your build tool to generate SCIP.
 
 ```sh
-# At the root of a Gradle, Maven or sbt codebase.
+# At the root of a Gradle or Maven codebase.
 $ scip-java index
 ...
 info: /path/to/index.scip
 ```
 
-| Build tool | Default command                                                                 |
-| ---------- | ------------------------------------------------------------------------------- |
-| Gradle     | `clean compileTestJava compileTestScala compileTestKotlin compileTestKotlinJvm` |
-| Maven      | `--batch-mode clean verify -DskipTests`                                         |
-| sbt        | `sourcegraphEnable sourcegraphScip` (via sbt-sourcegraph plugin)                |
-| Mill       | `io.kipp.mill.scip.Scip/generate` (via mill-scip plugin)                        |
+| Build tool | Default command                                            |
+| ---------- | ---------------------------------------------------------- |
+| Gradle     | `clean compileTestJava compileTestKotlin compileTestKotlinJvm` |
+| Maven      | `--batch-mode clean verify -DskipTests`                    |
 
 Customize the build command by passing additional arguments after
 `scip-java index --`.
@@ -208,11 +199,10 @@ com.sourcegraph.scip_java.ScipJava.printHelp(Console.out)
 
 ## Supported programming languages
 
-| Programming language | Gradle | Maven | sbt | Mill | Tracking issue                                              |
-| -------------------- | ------ | ----- | --- | ---- | ----------------------------------------------------------- |
-| Java                 | ✅     | ✅    | ✅  | ✅   |                                                             |
-| Scala                | ✅     | ❌    | ✅  | ✅   | [#302](https://github.com/sourcegraph/scip-java/issues/302) |
-| Kotlin               | ✅     | ❌    | n/a | n/a  |                                                             |
+| Programming language | Gradle | Maven | Tracking issue |
+| -------------------- | ------ | ----- | -------------- |
+| Java                 | ✅     | ✅    |                |
+| Kotlin               | ✅     | ❌    |                |
 
 ### Java
 
@@ -239,26 +229,11 @@ For Java 17 and newer versions, the following JVM options are required:
 --add-exports jdk.compiler/com.sun.tools.javac.code=ALL-UNNAMED
 ```
 
-### Scala
-
-Scala version support should always match the Scala versions that are supported
-by [Metals](https://scalameta.org/metals), the Scala language server.
-
-| Scala version | Goto definition | Find references | Hover |
-| ------------- | --------------- | --------------- | ----- |
-| Scala 2.11.x  | ❌              | ❌              | ❌    |
-| Scala 2.12.x  | ❌              | ❌              | ❌    |
-| Scala 2.13.x  | ✅              | ✅              | ✅    |
-| Scala 3.x     | ✅              | ✅              | ❌    |
-
-> Scala.js and Scala Native have equal support as Scala on the JVM.
-
 ### Kotlin
 
-The Kotlin support in scip-java is less mature compared to the Java and Scala
-support. Don't hesitate to report issues at
-https://github.com/sourcegraph/scip-java if you encounter issues using the
-Kotlin support.
+The Kotlin support in scip-java is less mature compared to the Java support.
+Don't hesitate to report issues at https://github.com/sourcegraph/scip-java if
+you encounter issues using the Kotlin support.
 
 ## Supported build tools
 
@@ -271,15 +246,13 @@ tools may require [manual configuration](manual-configuration.md).
 Please open an issue if your build tool is not listed in the table below. Feel
 free to subscribe to the tracking issues to receive updates on your build tool.
 
-| Build tool | Java | Scala | Kotlin | Tracking issue                                                                   |
-| ---------- | ---- | ----- | ------ | -------------------------------------------------------------------------------- |
-| Maven      | ✅   | ❌    | ❌     |                                                                                  |
-| Gradle     | ✅   | ✅    | ✅     |                                                                                  |
-| sbt        | ✅   | ✅    | n/a    |                                                                                  |
-| Ant        | ❌   | ❌    | ❌     | [sourcegraph/scip-java#305](https://github.com/sourcegraph/scip-java/issues/305) |
-| Bazel      | ✅   | ✅    | ❌     |                                                                                  |
-| Buck       | ❌   | ❌    | ❌     | [sourcegraph/scip-java#99](https://github.com/sourcegraph/scip-java/issues/99)   |
-| Mill       | ✅   | ✅    | ❌     |
+| Build tool | Java | Kotlin | Tracking issue                                                                   |
+| ---------- | ---- | ------ | -------------------------------------------------------------------------------- |
+| Maven      | ✅   | ❌     |                                                                                  |
+| Gradle     | ✅   | ✅     |                                                                                  |
+| Ant        | ❌   | ❌     | [sourcegraph/scip-java#305](https://github.com/sourcegraph/scip-java/issues/305) |
+| Bazel      | ✅   | ❌     |                                                                                  |
+| Buck       | ❌   | ❌     | [sourcegraph/scip-java#99](https://github.com/sourcegraph/scip-java/issues/99)   |
 
 **✅**: automatic indexing is fully supported. Please report a bug if the
 `scip-java index` command does not work on your codebase.
@@ -310,7 +283,6 @@ The following Gradle integrations are not yet supported:
 | ----------- | --------- | -------------------------------------------------------------------------------- |
 | Android     | ❌        | [sourcegraph/scip-java#177](https://github.com/sourcegraph/scip-java/issues/177) |
 | Kotlin      | ✅        |                                                                                  |
-| Scala       | ✅        |                                                                                  |
 
 ### Maven
 
@@ -322,29 +294,8 @@ The following Maven integrations are not yet supported:
 
 | Integration         | Supported | Tracking issue                                                                   |
 | ------------------- | --------- | -------------------------------------------------------------------------------- |
-| scala-maven-plugin  | ❌        | [sourcegraph/scip-java#301](https://github.com/sourcegraph/scip-java/issues/301) |
-| scalor-maven-plugin | ❌        | [sourcegraph/scip-java#301](https://github.com/sourcegraph/scip-java/issues/301) |
 | kotlin-maven-plugin | ❌        | [sourcegraph/scip-java#304](https://github.com/sourcegraph/scip-java/issues/304) |
 
-### sbt
-
-The `scip-java index` build should be able to automatically index most sbt
-projects, with the following caveats:
-
-| Integration   | Supported | Recommendation          |
-| ------------- | --------- | ----------------------- |
-| sbt <v0.13.17 | ❌        | Upgrade to sbt v0.13.17 |
-
-### Mill
-
-The `scip-java index` build should be able to automatically index most Mill
-projects, with the following caveats:
-
-| Integration   | Supported           | Recommendation                              |
-| ------------- | ------------------- | ------------------------------------------- |
-| Mill <v0.10.0 | ❌                  | Upgrade to Mill >= v0.10.0                  |
-| Mill <v0.10.6 | Only supports Scala | Upgrade to Mill >= v0.10.6 for Java support |
-
 ### Bazel
 
 There are two approaches to index Bazel/Java codebases: automatic and manual.

docs/manual-configuration.md

@@ -54,12 +54,6 @@ If you're using Maven.
 </dependency>
 ```
 
-If you're using sbt.
-
-```scala
-libraryDependencies += "com.sourcegraph" % "semanticdb-javac" % "@STABLE_VERSION@"
-```
-
 ## Step 2: Enable `-Xplugin:semanticdb` compiler option
 
 Add `-Xplugin:semanticdb` to your compiler options to enable the SemanticDB
@@ -108,17 +102,6 @@ If you're using Maven.
  </project>
 ```
 
-If you're using sbt.
-
-```scala
-javaHome := Some(...) // Must be configured to fork the compiler.
-Compile / javacOptions += {
-    val sourceroot = (ThisBuild / baseDirectory).value
-    val targetroot = sourceroot / "target" / "semanticdb-targetroot"
-    s"-Xplugin:semanticdb -sourceroot:$sourceroot -targetroot:$targetroot"
-}
-```
-
 ## Step 3: Compile the codebase
 
 Compile all source files in the codebase once the compiler setting has been
@@ -127,7 +110,6 @@ examples:
 
 - Gradle: `./gradlew clean compileJava compileTestJava`
 - Maven: `mvn clean verify -DskipTests`
-- sbt: `sbt clean test:compile`
 - Bazel: `bazel build //...`
 
 If everything went well, you should have a lot of `*.semanticdb` files in the

flake.nix

@@ -29,7 +29,6 @@
               jdk
               jq
               (maven.override ({ jdk_headless = jdk; }))
-              (mill.override ({ jre = jdk; }))
               nixfmt
               nodejs
               (sbt.override ({ jre = jdk; }))

project/plugins.sbt

@@ -5,7 +5,6 @@ addSbtPlugin("com.eed3si9n" % "sbt-buildinfo" % "0.10.0")
 addSbtPlugin("org.scalameta" % "sbt-scalafmt" % "2.5.5")
 addSbtPlugin("ch.epfl.scala" % "sbt-scalafix" % "0.14.3")
 addSbtPlugin("com.thesamet" % "sbt-protoc" % "1.0.6")
-addSbtPlugin("com.sourcegraph" % "sbt-sourcegraph" % "0.4.4")
 addSbtPlugin("com.lightbend.sbt" % "sbt-java-formatter" % "0.6.1")
 addSbtPlugin("pl.project13.scala" % "sbt-jmh" % "0.4.3")
 addSbtPlugin("com.eed3si9n" % "sbt-assembly" % "0.15.0")
@@ -15,8 +14,5 @@ addSbtPlugin("com.github.sbt.junit" % "sbt-jupiter-interface" % "0.15.1")
 // [error] (plugin / Compile / compileIncremental) java.lang.NoClassDefFoundError: com/sun/tools/javac/code/Symbol
 addSbtPlugin("org.scala-debugger" % "sbt-jdi-tools" % "1.1.1")
 
-libraryDependencies ++=
-  List("com.thesamet.scalapb" %% "compilerplugin" % "0.11.11")
-
 ThisBuild / libraryDependencySchemes ++=
   Seq("org.scala-lang.modules" %% "scala-xml" % VersionScheme.Always)