Remove Agg in favor of Seq (#4525)

Fixes #3587 * In most scenarios `Seq` is fine. * `Loose.Agg.Mutable` can be safely replaced by `collection.mutable.LinkedHashSet`, which behaves the same * `Strict.Agg` can be safely replaced by `Seq`, since any divergence from `Seq` behavior would throw an exception today. There is a slight loss in safety (e.g. if future bugs cause duplicates to occur) and with a slight gain in performance (since we no longer maintain two duplicate `Set`/`Seq` data structures * We leave a `type Agg[+T] = Seq[T]; val Agg = Seq` alias in the `package.scala` file to ease in the migration. This lets downstream users continue to use the name `Agg` in an _almost_ source compatible way (exception: `Agg.when` doesn't have a `Seq.when` equivalent), and also means we don't need to update `ci/mill-bootstrap.patch` due to source compatibility
com-lihaoyi · Feb 11, 2025 · 15f55d8 · 15f55d8
1 parent 147e0f1
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diff --git a/bsp/src/mill/bsp/BSP.scala b/bsp/src/mill/bsp/BSP.scala
@@ -1,7 +1,7 @@
 package mill.bsp
 
 import mill.api.{Ctx, PathRef}
-import mill.{Agg, T, Task, given}
+import mill.{T, Task, given}
 import mill.define.{Command, Discover, ExternalModule}
 import mill.main.BuildInfo
 import mill.eval.Evaluator
@@ -12,7 +12,7 @@ object BSP extends ExternalModule with CoursierModule {
 
   lazy val millDiscover = Discover[this.type]
 
-  private def bspWorkerLibs: T[Agg[PathRef]] = Task {
+  private def bspWorkerLibs: T[Seq[PathRef]] = Task {
     millProjectModule("mill-bsp-worker", repositoriesTask())
   }
 

diff --git a/bsp/worker/src/mill/bsp/worker/MillBuildServer.scala b/bsp/worker/src/mill/bsp/worker/MillBuildServer.scala
@@ -3,15 +3,8 @@ package mill.bsp.worker
 import ch.epfl.scala.bsp4j
 import ch.epfl.scala.bsp4j._
 import com.google.gson.JsonObject
-import mill.api.Loose.Agg
-import mill.api.{
-  ColorLogger,
-  CompileProblemReporter,
-  DummyTestReporter,
-  Result,
-  Strict,
-  TestReporter
-}
+
+import mill.api.{ColorLogger, CompileProblemReporter, DummyTestReporter, Result, TestReporter}
 import mill.bsp.{BspServerResult, Constants}
 import mill.bsp.worker.Utils.{makeBuildTarget, outputPaths, sanitizeUri}
 import mill.define.Segment.Label
@@ -479,7 +472,7 @@ private class MillBuildServer(
       val runTask = module.run(Task.Anon(Args(args)))
       val runResult = evaluate(
         ev,
-        Strict.Agg(runTask),
+        Seq(runTask),
         Utils.getBspLoggedReporterPool(runParams.getOriginId, state.bspIdByModule, client),
         logger = new MillBspLogger(client, runTask.hashCode(), ev.baseLogger)
       )
@@ -544,7 +537,7 @@ private class MillBuildServer(
 
               val results = evaluate(
                 ev,
-                Strict.Agg(testTask),
+                Seq(testTask),
                 Utils.getBspLoggedReporterPool(
                   testParams.getOriginId,
                   state.bspIdByModule,
@@ -605,7 +598,7 @@ private class MillBuildServer(
             val cleanTask = mainModule.clean(ev, Seq(compileTargetName)*)
             val cleanResult = evaluate(
               ev,
-              Strict.Agg(cleanTask),
+              Seq(cleanTask),
               logger = new MillBspLogger(client, cleanTask.hashCode, ev.baseLogger)
             )
             if (cleanResult.failing.size > 0) (
@@ -807,7 +800,7 @@ private class MillBuildServer(
 
   private def evaluate(
       evaluator: Evaluator,
-      goals: Agg[Task[?]],
+      goals: Seq[Task[?]],
       reporter: Int => Option[CompileProblemReporter] = _ => Option.empty[CompileProblemReporter],
       testReporter: TestReporter = DummyTestReporter,
       logger: ColorLogger = null

diff --git a/bsp/worker/src/mill/bsp/worker/MillScalaBuildServer.scala b/bsp/worker/src/mill/bsp/worker/MillScalaBuildServer.scala
@@ -13,7 +13,7 @@ import ch.epfl.scala.bsp4j.{
   ScalacOptionsParams,
   ScalacOptionsResult
 }
-import mill.{Agg, Task}
+import mill.Task
 import mill.bsp.worker.Utils.sanitizeUri
 import mill.util.Jvm
 import mill.scalalib.{JavaModule, ScalaModule, TestModule, UnresolvedPath}
@@ -41,7 +41,7 @@ private trait MillScalaBuildServer extends ScalaBuildServer { this: MillBuildSer
           val compileClasspathTask =
             if (enableJvmCompileClasspathProvider) {
               // We have a dedicated request for it
-              Task.Anon { Agg.empty[UnresolvedPath] }
+              Task.Anon { Seq.empty[UnresolvedPath] }
             } else {
               m.bspCompileClasspath
             }
@@ -119,7 +119,7 @@ private trait MillScalaBuildServer extends ScalaBuildServer { this: MillBuildSer
       }
     ) {
       case (ev, state, id, m: TestModule, Some((classpath, testFramework, testClasspath))) =>
-        val (frameworkName, classFingerprint): (String, Agg[(Class[?], Fingerprint)]) =
+        val (frameworkName, classFingerprint): (String, Seq[(Class[?], Fingerprint)]) =
           Jvm.withClassLoader(
             classPath = classpath.map(_.path).toVector,
             sharedPrefixes = Seq("sbt.testing.")
@@ -128,7 +128,7 @@ private trait MillScalaBuildServer extends ScalaBuildServer { this: MillBuildSer
             val discoveredTests = TestRunnerUtils.discoverTests(
               classLoader,
               framework,
-              Agg.from(testClasspath.map(_.path))
+              Seq.from(testClasspath.map(_.path))
             )
             (framework.name(), discoveredTests)
           }: @unchecked

diff --git a/ci/mill-bootstrap.patch b/ci/mill-bootstrap.patch
@@ -1,5 +1,5 @@
 diff --git a/build.mill b/build.mill
-index 7a8ea3a31a5..5b77aa31591 100644
+index 019adfc8cb9..c9df11158ef 100644
 --- a/build.mill
 +++ b/build.mill
 @@ -1,16 +1,16 @@
@@ -65,7 +65,25 @@ index 7a8ea3a31a5..5b77aa31591 100644
    def scalaVersion = Deps.scalaVersion
    def scalapVersion: T[String] = Deps.scala2Version
    def scalafixScalaBinaryVersion = T {
-@@ -535,7 +535,7 @@ trait MillScalaModule extends ScalaModule with MillJavaModule with ScalafixModul
+@@ -520,8 +520,8 @@ trait MillScalaModule extends ScalaModule with MillJavaModule with ScalafixModul
+     val binaryVersion = ZincWorkerUtil.scalaBinaryVersion(sv)
+     val hasModuleDefs = binaryVersion == "2.13" || binaryVersion == "3"
+     super.scalacPluginIvyDeps() ++
+-      Agg.when(binaryVersion != "3")(Deps.acyclic) ++
+-      Agg.when(hasModuleDefs)(Deps.millModuledefsPlugin)
++      Option.when(binaryVersion != "3")(Deps.acyclic) ++
++      Option.when(hasModuleDefs)(Deps.millModuledefsPlugin)
+   }
+
+   def mandatoryIvyDeps = T {
+@@ -529,13 +529,13 @@ trait MillScalaModule extends ScalaModule with MillJavaModule with ScalafixModul
+     val binaryVersion = ZincWorkerUtil.scalaBinaryVersion(sv)
+     val hasModuleDefs = binaryVersion == "2.13" || binaryVersion == "3"
+     super.mandatoryIvyDeps() ++
+-      Agg.when(hasModuleDefs)(Deps.millModuledefs)
++      Option.when(hasModuleDefs)(Deps.millModuledefs)
+   }
+
    /** Default tests module. */
    lazy val test: MillScalaTests = new MillScalaTests {}
    trait MillScalaTests extends ScalaTests with MillJavaModule with MillBaseTestsModule
@@ -94,7 +112,7 @@ index 7a8ea3a31a5..5b77aa31591 100644
 
  object bridge extends Cross[BridgeModule](compilerBridgeScalaVersions)
 diff --git a/contrib/package.mill b/contrib/package.mill
-index 421b2955955..7277bba90ff 100644
+index 421b2955955..30c453234b9 100644
 --- a/contrib/package.mill
 +++ b/contrib/package.mill
 @@ -3,13 +3,12 @@ package build.contrib
@@ -141,6 +159,15 @@ index 421b2955955..7277bba90ff 100644
        }
 
        def scalaVersion = build.Deps.play(playBinary).scalaVersion
+@@ -139,7 +138,7 @@ object `package` extends RootModule {
+           build.Deps.scalacScoverage2Reporter,
+           build.Deps.scalacScoverage2Domain,
+           build.Deps.scalacScoverage2Serializer
+-        ) ++ Agg.when(!ZincWorkerUtil.isScala3(scalaVersion()))(build.Deps.scalacScoverage2Plugin)
++        ) ++ Option.when(!ZincWorkerUtil.isScala3(scalaVersion()))(build.Deps.scalacScoverage2Plugin)
+       }
+       def mandatoryIvyDeps = Agg.empty[Dep]
+     }
 diff --git a/core/codesig/package.mill b/core/codesig/package.mill
 index e49f218f4be..9d03aa073f3 100644
 --- a/core/codesig/package.mill

diff --git a/contrib/bloop/src/mill/contrib/bloop/BloopImpl.scala b/contrib/bloop/src/mill/contrib/bloop/BloopImpl.scala
@@ -191,7 +191,7 @@ class BloopImpl(evs: () => Seq[Evaluator], wd: os.Path) extends ExternalModule {
 
     val classpath = Task.Anon {
       val transitiveCompileClasspath = Task.traverse(module.transitiveModuleCompileModuleDeps)(m =>
-        Task.Anon { m.localCompileClasspath().map(_.path) ++ Agg(classes(m)) }
+        Task.Anon { m.localCompileClasspath().map(_.path) ++ Seq(classes(m)) }
       )().flatten
 
       module.resolvedIvyDeps().map(_.path) ++

diff --git a/contrib/bloop/test/src/mill/contrib/bloop/BloopTests.scala b/contrib/bloop/test/src/mill/contrib/bloop/BloopTests.scala
@@ -27,18 +27,18 @@ object BloopTests extends TestSuite {
       val bloopVersion = mill.contrib.bloop.Versions.bloop
       override def mainClass = Some("foo.bar.Main")
 
-      override def ivyDeps = Agg(
+      override def ivyDeps = Seq(
         ivy"ch.epfl.scala::bloop-config:$bloopVersion"
       )
       override def scalacOptions = Seq(
         "-language:higherKinds"
       )
 
-      override def compileIvyDeps = Agg(
+      override def compileIvyDeps = Seq(
         ivy"org.reactivestreams:reactive-streams:1.0.3"
       )
 
-      override def runIvyDeps = Agg(
+      override def runIvyDeps = Seq(
         ivy"org.postgresql:postgresql:42.3.3"
       )
 

diff --git a/contrib/flyway/readme.adoc b/contrib/flyway/readme.adoc
@@ -20,7 +20,7 @@ object foo extends ScalaModule with FlywayModule {
 
   //region flyway
   def flywayUrl = "jdbc:postgresql:myDb" // required
-  def flywayDriverDeps = Agg(ivy"org.postgresql:postgresql:42.2.5") // required
+  def flywayDriverDeps = Seq(ivy"org.postgresql:postgresql:42.2.5") // required
   def flywayUser = "postgres" // optional
   // def flywayPassword = "" // optional
   //endregion

diff --git a/contrib/flyway/src/mill/contrib/flyway/FlywayModule.scala b/contrib/flyway/src/mill/contrib/flyway/FlywayModule.scala
@@ -10,7 +10,7 @@ import org.flywaydb.core.internal.configuration.{ConfigUtils => flyway}
 import org.flywaydb.core.internal.info.MigrationInfoDumper
 import scala.jdk.CollectionConverters._
 
-import mill.{Agg, T, Task}
+import mill.{T, Task}
 import mill.api.PathRef
 import mill.define.Command
 import mill.scalalib.{Dep, JavaModule}
@@ -26,7 +26,7 @@ trait FlywayModule extends JavaModule {
     resources().map(pr => PathRef(pr.path / "db/migration", pr.quick))
   }
 
-  def flywayDriverDeps: T[Agg[Dep]]
+  def flywayDriverDeps: T[Seq[Dep]]
 
   def jdbcClasspath = Task {
     defaultResolver().resolveDeps(flywayDriverDeps())

diff --git a/contrib/flyway/test/src/mill/contrib/flyway/BuildTest.scala b/contrib/flyway/test/src/mill/contrib/flyway/BuildTest.scala
@@ -18,7 +18,7 @@ object BuildTest extends TestSuite {
       def h2 = ivy"com.h2database:h2:2.1.214"
 
       def flywayUrl = "jdbc:h2:mem:test_db;DB_CLOSE_DELAY=-1"
-      def flywayDriverDeps = Agg(h2)
+      def flywayDriverDeps = Seq(h2)
     }
 
     val millDiscover: Discover = Discover[this.type]

diff --git a/contrib/jmh/src/mill/contrib/jmh/JmhModule.scala b/contrib/jmh/src/mill/contrib/jmh/JmhModule.scala
@@ -33,7 +33,7 @@ trait JmhModule extends JavaModule {
   def jmhCoreVersion: T[String]
   def jmhGeneratorByteCodeVersion: T[String] = jmhCoreVersion
 
-  def ivyDeps = super.ivyDeps() ++ Agg(ivy"org.openjdk.jmh:jmh-core:${jmhCoreVersion()}")
+  def ivyDeps = super.ivyDeps() ++ Seq(ivy"org.openjdk.jmh:jmh-core:${jmhCoreVersion()}")
 
   def runJmh(args: String*) =
     Task.Command {
@@ -105,7 +105,7 @@ trait JmhModule extends JavaModule {
 
   def generatorDeps = Task {
     defaultResolver().resolveDeps(
-      Agg(ivy"org.openjdk.jmh:jmh-generator-bytecode:${jmhGeneratorByteCodeVersion()}")
+      Seq(ivy"org.openjdk.jmh:jmh-generator-bytecode:${jmhGeneratorByteCodeVersion()}")
     )
   }
 }
diff --git a/contrib/playlib/readme.adoc b/contrib/playlib/readme.adoc
@@ -78,7 +78,7 @@ The following compile dependencies will automatically be added to your build:
 
 [source,scala]
 ----
-Agg(
+Seq(
   ivy"com.typesafe.play::play:${playVersion()}",
   ivy"com.typesafe.play::play-guice:${playVersion()}",
   ivy"com.typesafe.play::play-server:${playVersion()}",
@@ -162,7 +162,7 @@ object core extends PlayApiModule {
 
     object test extends PlayTests
 
-    override def ivyDeps = Task { super.ivyDeps() ++ Agg(ws(), filters()) }
+    override def ivyDeps = Task { super.ivyDeps() ++ Seq(ws(), filters()) }
 }
 ----
 

diff --git a/contrib/playlib/src/mill/playlib/Dependencies.scala b/contrib/playlib/src/mill/playlib/Dependencies.scala
@@ -1,6 +1,6 @@
 package mill.playlib
 
-import mill.{Agg, Task}
+import mill.Task
 import mill.scalalib._
 
 private[playlib] trait Dependencies extends ScalaModule with Version {
@@ -15,7 +15,7 @@ private[playlib] trait Dependencies extends ScalaModule with Version {
   def caffeine = Task { component("play-caffeine-cache")() }
 
   override def ivyDeps = Task {
-    super.ivyDeps() ++ Agg(
+    super.ivyDeps() ++ Seq(
       core(),
       guice(),
       server(),

diff --git a/contrib/playlib/src/mill/playlib/PlayModule.scala b/contrib/playlib/src/mill/playlib/PlayModule.scala
@@ -3,7 +3,7 @@ package mill.playlib
 import mill.define.Task
 import mill.playlib.api.Versions
 import mill.scalalib._
-import mill.{Agg, Args, T}
+import mill.{Args, T}
 import mill.api.PathRef
 import mill.define.Target
 
@@ -17,7 +17,7 @@ trait PlayApiModule extends Dependencies with Router with Server {
         case Versions.PLAY_2_9 => "6.0.0"
         case _ => "7.0.0"
       }
-      Agg(ivy"org.scalatestplus.play::scalatestplus-play::${scalatestPlusPlayVersion}")
+      Seq(ivy"org.scalatestplus.play::scalatestplus-play::${scalatestPlusPlayVersion}")
     }
     override def sources: Target[Seq[PathRef]] = Task.Sources { moduleDir }
   }

diff --git a/contrib/playlib/src/mill/playlib/RouteCompilerWorker.scala b/contrib/playlib/src/mill/playlib/RouteCompilerWorker.scala
@@ -3,14 +3,14 @@ package mill.playlib
 import mill.api.{Ctx, PathRef, Result}
 import mill.playlib.api.{RouteCompilerType, RouteCompilerWorkerApi}
 import mill.scalalib.api.CompilationResult
-import mill.{Agg, Task}
+import mill.Task
 
 private[playlib] class RouteCompilerWorker extends AutoCloseable {
 
   private var routeCompilerInstanceCache =
     Option.empty[(Long, mill.playlib.api.RouteCompilerWorkerApi)]
 
-  protected def bridge(toolsClasspath: Agg[PathRef])(
+  protected def bridge(toolsClasspath: Seq[PathRef])(
       implicit ctx: Ctx
   ): RouteCompilerWorkerApi = {
     val classloaderSig = toolsClasspath.hashCode
@@ -35,7 +35,7 @@ private[playlib] class RouteCompilerWorker extends AutoCloseable {
   }
 
   def compile(
-      routerClasspath: Agg[PathRef],
+      routerClasspath: Seq[PathRef],
       files: Seq[os.Path],
       additionalImports: Seq[String],
       forwardsRouter: Boolean,

diff --git a/contrib/playlib/src/mill/playlib/RouterModule.scala b/contrib/playlib/src/mill/playlib/RouterModule.scala
@@ -5,7 +5,7 @@ import mill.util.MillModuleUtil.millProjectModule
 import mill.playlib.api.RouteCompilerType
 import mill.scalalib._
 import mill.scalalib.api._
-import mill.{Agg, T, Task}
+import mill.{T, Task}
 
 trait RouterModule extends ScalaModule with Version {
 
@@ -45,15 +45,15 @@ trait RouterModule extends ScalaModule with Version {
    */
   def generatorType: RouteCompilerType = RouteCompilerType.InjectedGenerator
 
-  def routerClasspath: T[Agg[PathRef]] = Task {
+  def routerClasspath: T[Seq[PathRef]] = Task {
     defaultResolver().resolveDeps(
       playMinorVersion() match {
         case "2.6" | "2.7" | "2.8" =>
-          Agg(ivy"com.typesafe.play::routes-compiler:${playVersion()}")
+          Seq(ivy"com.typesafe.play::routes-compiler:${playVersion()}")
         case "2.9" =>
-          Agg(ivy"com.typesafe.play::play-routes-compiler:${playVersion()}")
+          Seq(ivy"com.typesafe.play::play-routes-compiler:${playVersion()}")
         case _ =>
-          Agg(ivy"org.playframework::play-routes-compiler:${playVersion()}")
+          Seq(ivy"org.playframework::play-routes-compiler:${playVersion()}")
       }
     )
   }

diff --git a/contrib/playlib/src/mill/playlib/Server.scala b/contrib/playlib/src/mill/playlib/Server.scala
@@ -1,7 +1,7 @@
 package mill.playlib
 
 import mill.scalalib._
-import mill.{Agg, Task}
+import mill.Task
 
 private[playlib] trait Server extends ScalaModule with Version {
 
@@ -19,7 +19,7 @@ private[playlib] trait Server extends ScalaModule with Version {
   }
 
   override def runIvyDeps = Task {
-    super.runIvyDeps() ++ Agg(playServerProvider())
+    super.runIvyDeps() ++ Seq(playServerProvider())
   }
 
   override def mainClass = Task { Some("play.core.server.ProdServerStart") }

diff --git a/contrib/playlib/test/src/mill/playlib/PlayModuleTests.scala b/contrib/playlib/test/src/mill/playlib/PlayModuleTests.scala
@@ -15,7 +15,7 @@ object PlayModuleTests extends TestSuite with PlayTestSuite {
       override def playVersion = crossPlayVersion
       override def scalaVersion = crossScalaVersion
       object test extends PlayTests
-      override def ivyDeps = Task { super.ivyDeps() ++ Agg(ws()) }
+      override def ivyDeps = Task { super.ivyDeps() ++ Seq(ws()) }
     }
 
     lazy val millDiscover = Discover[this.type]