Add Mill build (bare minimum changes check)

.github/scripts/setup-dev-mill.sh

@@ -0,0 +1,21 @@
+#!/usr/bin/env bash
+set -e
+
+if [ ! -e "$HOME/.ivy2/local/mill-proguard.jar" ]; then
+  MILL_COMMIT="de17c958012"
+
+  # Adding an extra directory "thing", to work around some Mill issue with scripts
+  mkdir thing
+  cd thing
+  git clone https://github.com/alexarchambault/mill.git -b scala3-new mill-scala3
+  cd mill-scala3
+  git switch --detach "$MILL_COMMIT"
+  ./mill -i dist.installLocal
+  mv mill-proguard.jar "$HOME/.ivy2/local/"
+  cd ..
+  cd ..
+  rm -rf thing
+fi
+
+ln -sf "$HOME/.ivy2/local/mill-proguard.jar" mill
+chmod +x mill

.github/workflows/ci.yml

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+name: CI
+on:
+  push:
+    branches:
+    - mill-build
+  pull_request:
+
+jobs:
+  compile-all:
+    runs-on: ubuntu-latest
+    timeout-minutes: 120
+    steps:
+    - uses: actions/checkout@v5
+      with:
+        fetch-depth: 0
+        # submodules: true
+    - uses: coursier/setup-action@v2
+    - name: Setup Mill
+      run: .github/scripts/setup-dev-mill.sh
+    - name: No modules with empty sources
+      run: ./mill -i ci.noEmptySources --tasks __.allSourceFiles
+    - name: No orphan sources
+      run: ./mill -i ci.noOrphanSources --sourceTasks '__.{allSourceFiles,compileResources}'
+    - name: Compile everything
+      run: ./mill -i __.compile
+    - name: Pre-upload artifact
+      run: |
+        mv ~/.cache/coursier/v1 coursier-cache
+        mv ~/.cache/mill mill-cache
+        if test -d ~/.cache/mill/download; then
+          chmod +x ~/.cache/mill/download/*
+        fi
+        mkdir -p ~/.ivy2/local
+        mv ~/.ivy2/local ivy2-local
+    - name: Upload build output
+      uses: actions/upload-artifact@v4
+      with:
+        name: out
+        path: out
+        if-no-files-found: error
+        retention-days: 3
+    - name: Upload coursier cache
+      uses: actions/upload-artifact@v4
+      with:
+        name: coursier-cache
+        path: coursier-cache
+        if-no-files-found: error
+        retention-days: 3
+    - name: Upload Mill cache
+      uses: actions/upload-artifact@v4
+      with:
+        name: mill-cache
+        path: mill-cache
+        if-no-files-found: error
+        retention-days: 3
+    - name: Upload ivy2 local
+      uses: actions/upload-artifact@v4
+      with:
+        name: ivy2-local
+        path: ivy2-local
+        if-no-files-found: error
+        retention-days: 3
+
+  repl-test:
+    runs-on: ubuntu-latest
+    needs: compile-all
+    timeout-minutes: 15
+    steps:
+    - uses: actions/checkout@v5
+      with:
+        fetch-depth: 0
+    - uses: actions/download-artifact@v4
+      with:
+        name: out
+        path: out
+    - uses: actions/download-artifact@v4
+      with:
+        name: coursier-cache
+        path: coursier-cache
+    - uses: actions/download-artifact@v4
+      with:
+        name: mill-cache
+        path: mill-cache
+    - uses: actions/download-artifact@v4
+      with:
+        name: ivy2-local
+        path: ivy2-local
+    - name: Post-download artifacts
+      run: |
+        mkdir -p ~/.cache/coursier
+        mv coursier-cache ~/.cache/coursier/v1
+        mv mill-cache ~/.cache/mill
+        if test -d ~/.cache/mill/download; then
+          chmod +x ~/.cache/mill/download/*
+        fi
+        mkdir -p ~/.ivy2
+        mv ivy2-local ~/.ivy2/local
+    - uses: coursier/setup-action@v2
+    - name: Install expect
+      run: |
+        sudo apt-get update
+        sudo apt-get install -y expect
+        expect -v
+    - name: Setup Mill
+      run: .github/scripts/setup-dev-mill.sh
+    - name: Prepare for REPL test
+      run: ./mill -i 'repl[final].compile'
+    - name: Run REPL test
+      env:
+        TERM: dumb
+      run: project/scripts/mill-repl-test.expect
+
+  tests:
+    runs-on: ubuntu-latest
+    needs: compile-all
+    name: ${{ matrix.BUILD_TYPE }}
+    strategy:
+      fail-fast: false
+      matrix:
+        BUILD_TYPE: ["bootstrapping", "final"]
+        TEST: ["test", "full-test"]
+    timeout-minutes: 120
+    steps:
+    - uses: actions/checkout@v5
+      with:
+        fetch-depth: 0
+        # submodules: true
+    - uses: actions/download-artifact@v4
+      with:
+        name: out
+        path: out
+    - uses: actions/download-artifact@v4
+      with:
+        name: coursier-cache
+        path: coursier-cache
+    - uses: actions/download-artifact@v4
+      with:
+        name: mill-cache
+        path: mill-cache
+    - uses: actions/download-artifact@v4
+      with:
+        name: ivy2-local
+        path: ivy2-local
+    - name: Post-download artifacts
+      run: |
+        mkdir -p ~/.cache/coursier
+        mv coursier-cache ~/.cache/coursier/v1
+        mv mill-cache ~/.cache/mill
+        if test -d ~/.cache/mill/download; then
+          chmod +x ~/.cache/mill/download/*
+        fi
+        mkdir -p ~/.ivy2
+        mv ivy2-local ~/.ivy2/local
+    - uses: coursier/setup-action@v2
+    - name: Setup Mill
+      run: .github/scripts/setup-dev-mill.sh
+    - name: Test
+      run: ./mill -i '__[${{ matrix.BUILD_TYPE }}].${{ matrix.TEST }}'
+      env:
+        DOTTY_CI_RUN: true

build.mill

@@ -0,0 +1,105 @@
+//| mill-version: 1.1.2
+//| bspScriptIgnore:
+//| - ".plasmon/"
+//| - "bench/"
+//| - "bin/"
+//| - "community-build/"
+//| - "compiler/test/"
+//| - "compiler/test-resources/"
+//| - "language-server/"
+//| - "project/"
+//| - "repl/test/"
+//| - "repl/test-resources/"
+//| - "sandbox/"
+//| - "sbt-test/"
+//| - "scaladoc/"
+//| - "scaladoc-js/"
+//| - "sjs-compiler-tests/"
+//| - "tests/"
+
+package build
+
+import mill.*
+import mill.util.Tasks
+import mill.api.BuildCtx
+import mill.constants.OutFiles
+
+object ci extends Module {
+
+  val allowEmptySources = Set(
+    "sjs-compiler-tests.bootstrapping",
+    "sjs-compiler-tests.final"
+  )
+
+  def noEmptySources(tasks: mill.util.Tasks[Seq[PathRef]]) = Task.Command[Unit] {
+    val values = tasks.value.zip(Task.sequence(tasks.value)())
+    val invalid = values
+      .filter(_._2.isEmpty)
+      .filter {
+        case (m, _) =>
+          val moduleName = m.toString.stripSuffix(".allSourceFiles")
+          !allowEmptySources.contains(moduleName)
+      }
+
+    if (invalid.nonEmpty) {
+      System.err.println("Found modules with no sources:")
+      for ((m, _) <- invalid)
+        System.err.println(s"  $m")
+      sys.error(s"Found modules with no sources: ${invalid.map(_._1).mkString(", ")}")
+    }
+  }
+
+  def noOrphanSources(sourceTasks: Tasks[Seq[PathRef]]) = Task.Command[Unit] {
+    val allSources = Task.sequence(sourceTasks.value)()
+      .flatten
+      .map(_.path)
+      .filter(_.startsWith(BuildCtx.workspaceRoot))
+      .flatMap { path =>
+        if (os.isDir(path)) os.walk(path)
+        else Seq(path)
+      }
+      .map(_.subRelativeTo(BuildCtx.workspaceRoot))
+      .toSet
+
+    val ignore = Seq[os.SubPath](
+      "bench",
+      "bench-micro",
+      "bench-run",
+      "bin",
+      "library-aux", // Unused directory?
+      // See comment in library-js/package.mill about these two
+      "library-js/src/scala/math/ScalaNumber.scala",
+      "library-js/src/scala/runtime/BoxesRunTime.scala",
+      "mill-build",
+      "project",
+      "sbt-test",
+      "tests"
+    )
+
+    val outDir = BuildCtx.workspaceRoot / OutFiles.OutFiles.out
+    val foundFiles = os.walk(
+      BuildCtx.workspaceRoot,
+      skip = p =>
+        p.startsWith(outDir) || {
+          val subPath = p.subRelativeTo(BuildCtx.workspaceRoot)
+          (subPath.segments.length == 1 && subPath.segments.head.startsWith(".")) ||
+            ignore.exists(subPath.startsWith)
+        }
+    )
+    val foundSources = foundFiles
+      .filter(_.last.endsWith(".scala"))
+      .filter(os.isFile)
+      .map(_.subRelativeTo(BuildCtx.workspaceRoot))
+
+    pprint.err.log(foundSources.length)
+
+    val orphanSources = foundSources.filter(!allSources.contains(_))
+
+    if (orphanSources.nonEmpty) {
+      System.err.println(" Found orphan sources:")
+      for (f <- orphanSources)
+        System.err.println(s"  $f")
+      sys.error("Found orphan sources")
+    }
+  }
+}

community-build/package.mill

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+package build.`community-build`
+
+import scala3build.*
+
+import mill.*
+import mill.scalalib.*
+
+object `package` extends Scala3Module {
+  def moduleDeps = super.moduleDeps ++ Seq(
+    build.library(buildType)
+  )
+  def buildType = BuildType.Bootstrapping
+
+  def testSrc = Task.Source("test")
+
+  object test extends Scala3Tests {
+    def testSources = Task {
+      Seq(testSrc())
+    }
+
+    def testArgsDefault = super.testArgsDefault() ++ Seq(
+      "--include-categories=dotty.communitybuild.TestCategory",
+      "--run-listener=dotty.communitybuild.FailureSummarizer"
+    )
+  }
+}