Support mill init from an existing sbt project, and improve related Maven and Gradle support

.github/actions/post-build-setup/action.yml

@@ -34,4 +34,5 @@ runs:
         name: ${{ inputs.os }}-selective-execution-artifact
 
     - run: mv out/mill-selective-execution/mill-selective-execution.json out/mill-selective-execution.json
-      shell: bash
+      shell: bash
+

.github/actions/pre-build-setup/action.yml

@@ -65,4 +65,4 @@ runs:
     - uses: actions/checkout@v4
 
     - run: echo temurin:${{ inputs.java-version }} > .mill-jvm-version
-      shell: bash
+      shell: bash

.github/workflows/autofix.yml

@@ -7,6 +7,8 @@ jobs:
     steps:
       - uses: actions/checkout@v4
 
+      - uses: sbt/setup-sbt@v1
+
       - run: |
           ./mill __.fix + mill.javalib.palantirformat.PalantirFormatModule/ + mill.scalalib.scalafmt.ScalafmtModule/ + mill.kotlinlib.ktlint.KtlintModule/
           ./mill --meta-level 1 mill.scalalib.scalafmt.ScalafmtModule/

.github/workflows/post-build-selective.yml

@@ -26,6 +26,9 @@ on:
       install-android-sdk:
         default: false
         type: boolean
+      install-sbt:
+        default: false
+        type: boolean
 
 jobs:
   run:
@@ -48,6 +51,9 @@ jobs:
       - uses: ./.github/actions/setup-android
         if: ${{ inputs.install-android-sdk }}
 
+      - uses: sbt/setup-sbt@v1
+        if: ${{ inputs.install-sbt }}
+
       - uses: ./.github/actions/post-build-selective
 
         with:

.github/workflows/run-tests.yml

@@ -133,57 +133,75 @@ jobs:
           - java-version: 17
             millargs: "'{core,main,scalalib,testrunner,bsp,testkit}.__.test'"
             install-android-sdk: false
+            install-sbt: true
 
           - java-version: 11
             millargs: "'{scalajslib,scalanativelib,kotlinlib,pythonlib,javascriptlib}.__.test'"
             install-android-sdk: false
+            install-sbt: false
 
           - java-version: 17
             millargs: "contrib.__.test"
             install-android-sdk: false
+            install-sbt: false
 
           - java-version: 17
             millargs: "example.javalib.__.local.server.test"
             install-android-sdk: false
+            install-sbt: false
 
           - java-version: 17
             millargs: "example.kotlinlib.__.local.server.test"
             install-android-sdk: false
+            install-sbt: false
 
           # Run this one using `.native` as a smoketest. Also make sure the java-version
           # is the same as that used in the `build-linux` job to avoid diverging code
           # hashes (https://github.com/com-lihaoyi/mill/pull/4410)
           - java-version: 11
             millargs: "example.scalalib.__.native.server.test"
             install-android-sdk: false
+            install-sbt: false
 
           - java-version: 17
             millargs: "'example.android.__.local.server.test'"
             install-android-sdk: true
+            install-sbt: false
+
+          - java-version: 11
+            millargs: "'{example,integration}.migrating.__.local.server.test'"
+            install-android-sdk: false
+            install-sbt: true
 
           - java-version: 17
             millargs: "'example.{pythonlib,javascriptlib}.__.local.server.test'"
             install-android-sdk: false
+            install-sbt: false
 
           - java-version: 11
             millargs: "'example.thirdparty[{mockito,commons-io}].local.server.test'"
             install-android-sdk: false
+            install-sbt: false
 
           - java-version: 17
             millargs: "'example.thirdparty[{netty,gatling}].local.server.test'"
             install-android-sdk: false
+            install-sbt: false
 
           - java-version: '17'
             millargs: "'example.thirdparty[arrow].local.server.test'"
             install-android-sdk: false
+            install-sbt: false
 
           - java-version: 11
             millargs: "'example.{cli,fundamentals,depth,extending}.__.local.server.test'"
             install-android-sdk: false
+            install-sbt: false
 
           - java-version: 11
             millargs: "'integration.{failure,feature,ide}.__.packaged.server.test'"
             install-android-sdk: false
+            install-sbt: false
 
             # run this specifically in `native` mode to make sure our non-JVM native image
             # launcher is able to bootstrap everything necessary without a JVM installed
@@ -196,14 +214,17 @@ jobs:
           - java-version: 17
             millargs: "'integration.invalidation.__.packaged.fork.test'"
             install-android-sdk: false
+            install-sbt: false
 
           - java-version: 17
             millargs: "'integration.invalidation.__.packaged.server.test'"
             install-android-sdk: false
+            install-sbt: false
 
     uses: ./.github/workflows/post-build-selective.yml
     with:
       install-android-sdk: ${{ matrix.install-android-sdk }}
+      install-sbt: ${{ matrix.install-sbt }}
       java-version: ${{ matrix.java-version }}
       millargs: ${{ matrix.millargs }}
       shell: bash
@@ -222,15 +243,23 @@ jobs:
           # * At least one job for each of fork/server tests, and example/integration tests
           - java-version: 11
             millargs: '"{main,scalalib,bsp}.__.test"'
+            install-sbt: false
 
           - java-version: 11
             millargs: '"example.scalalib.{basic,publishing}.__.local.fork.test"'
+            install-sbt: false
+
+          - java-version: 11
+            millargs: '"example.migrating.{scalalib,javalib}.__.local.fork.test"'
+            install-sbt: true
 
           - java-version: 17
             millargs: "'integration.{feature,failure}.__.packaged.fork.test'"
+            install-sbt: false
 
           - java-version: 11 # Run this with Mill native launcher as a smoketest
             millargs: "'integration.invalidation.__.native.server.test'"
+            install-sbt: false
 
           - java-version: 17
             millargs: "'integration.bootstrap[no-java-bootstrap].native.server.test'"
@@ -244,6 +273,7 @@ jobs:
       # running the graal native image binary on windows
       coursierarchive: "C:/coursier-arc"
       shell: powershell
+      install-sbt: ${{ matrix.install-sbt }}
 
   itest:
     needs: build-linux

build.mill

@@ -55,6 +55,7 @@ object Deps {
   val scala2Version = "2.13.15"
   // The Scala 2.12.x version to use for some workers
   val workerScalaVersion212 = "2.12.20"
+  val sbtScalaVersion212 = workerScalaVersion212
 
   val testScala213Version = "2.13.15"
   // Scala Native 4.2 will not get releases for new Scala version
@@ -220,6 +221,7 @@ object Deps {
     ivy"org.apache.maven.resolver:maven-resolver-transport-wagon:$mavenResolverVersion"
   val coursierJvmIndexVersion = "0.0.4-84-f852c6"
   val gradleApi = ivy"dev.gradleplugins:gradle-api:8.11.1"
+  val sbt = ivy"org.scala-sbt:sbt:1.10.10"
 
   object RuntimeDeps {
     val dokkaVersion = "2.0.0"
@@ -568,7 +570,8 @@ trait MillBaseTestsModule extends TestModule {
       s"-DTEST_TEST_INTERFACE_VERSION=${Deps.sbtTestInterface.version}",
       s"-DTEST_ZIOTEST_VERSION=${Deps.TestDeps.zioTest.version}",
       s"-DTEST_ZINC_VERSION=${Deps.zinc.version}",
-      s"-DTEST_KOTLIN_VERSION=${Deps.kotlinCompiler.version}"
+      s"-DTEST_KOTLIN_VERSION=${Deps.kotlinCompiler.version}",
+      s"-DTEST_SBT_VERSION=${Deps.sbt.version}"
     )
   }
 
@@ -713,8 +716,10 @@ trait MillStableScalaModule extends MillPublishScalaModule with Mima {
   }
 }
 
+trait MillPublishCrossScalaModule extends MillPublishJavaModule with CrossScalaModule
+
 object bridge extends Cross[BridgeModule](compilerBridgeScalaVersions)
-trait BridgeModule extends MillPublishJavaModule with CrossScalaModule {
+trait BridgeModule extends MillPublishCrossScalaModule {
   def scalaVersion = crossScalaVersion
   def publishVersion = bridgeVersion
   def artifactName = "mill-scala-compiler-bridge"