Remove unnecessary .Sources (#4120)

Lots of these can just be normal `Task`s, since they simply rely on
upstream `Task.Sources` but do not add any source paths themselves. And
since 0.11.x they're all the same type anyway so changing back and forth
doesn't break compatibility

This speeds up `selective.prepare` on the com-lihaoyi/mill codebase
considerably, since we need to evaluate all sources (and their
transitive upstream tasks) up-front to decide what sources changed and
determine the downstream tasks to run. Before this PR this ended up
compiling a bunch of Scala code, after this PR it no longer does so

build.mill

@@ -606,7 +606,7 @@ trait BridgeModule extends MillPublishJavaModule with CrossScalaModule {
     ivy"org.scala-lang:scala-compiler:${crossScalaVersion}"
   )
 
-  def resources = Task.Sources {
+  def resources = Task {
     os.copy(generatedSources().head.path / "META-INF", Task.dest / "META-INF")
     Seq(PathRef(Task.dest))
   }

contrib/playlib/src/mill/playlib/Layout.scala

@@ -8,6 +8,6 @@ private[playlib] trait Layout extends JavaModule {
   def conf = Task.Sources { millSourcePath / "conf" }
   def app = Task.Sources { millSourcePath / "app" }
 
-  override def sources = Task.Sources { app() }
-  override def resources = Task.Sources { conf() }
+  override def sources = Task { app() }
+  override def resources = Task { conf() }
 }

contrib/playlib/src/mill/playlib/Twirl.scala

@@ -5,7 +5,7 @@ import mill.twirllib._
 
 trait Twirl extends TwirlModule with Layout {
 
-  override def twirlSources = Task.Sources { app() }
+  override def twirlSources = Task { app() }
 
   override def twirlImports = Task {
     super.twirlImports() ++ Seq(

contrib/playlib/test/src/mill/playlib/PlayModuleTests.scala

@@ -40,7 +40,7 @@ object PlayModuleTests extends TestSuite with PlayTestSuite {
               app.value.map(_.path.relativeTo(playmulti.millSourcePath).toString()) == Seq(
                 "core/app"
               ),
-              sources == app,
+              sources.value == app.value,
               resources.value.map(_.path.relativeTo(playmulti.millSourcePath).toString()).contains(
                 "core/conf"
               ),

contrib/playlib/test/src/mill/playlib/PlaySingleApiModuleTests.scala

@@ -38,8 +38,8 @@ object PlaySingleApiModuleTests extends TestSuite with PlayTestSuite {
             "conf"
           ),
           app.value.map(_.path.relativeTo(playsingleapi.millSourcePath).toString()) == Seq("app"),
-          sources == app,
-          resources == conf,
+          sources.value == app.value,
+          resources.value == conf.value,
           testSources.value.map(
             _.path.relativeTo(playsingleapi.millSourcePath).toString()
           ) == Seq(

contrib/playlib/test/src/mill/playlib/PlaySingleModuleTests.scala

@@ -27,7 +27,7 @@ object PlaySingleModuleTests extends TestSuite with PlayTestSuite {
         assert(
           conf.value.map(_.path.relativeTo(playsingle.millSourcePath).toString()) == Seq("conf"),
           app.value.map(_.path.relativeTo(playsingle.millSourcePath).toString()) == Seq("app"),
-          sources == app,
+          sources.value == app.value,
           resources.value.map(_.path.relativeTo(playsingle.millSourcePath).toString()).contains(
             "conf"
           ),

contrib/scoverage/src/mill/contrib/scoverage/ScoverageModule.scala

@@ -156,8 +156,8 @@ trait ScoverageModule extends ScalaModule { outer: ScalaModule =>
     override def allSources: T[Seq[PathRef]] = Task { outer.allSources() }
     override def moduleDeps: Seq[JavaModule] = outer.moduleDeps
     override def compileModuleDeps: Seq[JavaModule] = outer.compileModuleDeps
-    override def sources: T[Seq[PathRef]] = Task.Sources { outer.sources() }
-    override def resources: T[Seq[PathRef]] = Task.Sources { outer.resources() }
+    override def sources: T[Seq[PathRef]] = Task { outer.sources() }
+    override def resources: T[Seq[PathRef]] = Task { outer.resources() }
     override def scalaVersion = Task { outer.scalaVersion() }
     override def repositoriesTask: Task[Seq[Repository]] = Task.Anon { outer.repositoriesTask() }
     override def compileIvyDeps: T[Agg[Dep]] = Task { outer.compileIvyDeps() }

example/extending/metabuild/4-meta-build/build.mill

@@ -11,7 +11,7 @@ object `package` extends RootModule with ScalaModule {
   )
 
   def htmlSnippet = Task { h1("hello").toString }
-  def resources = Task.Sources {
+  def resources = Task {
     os.write(Task.dest / "snippet.txt", htmlSnippet())
     super.resources() ++ Seq(PathRef(Task.dest))
   }

example/pythonlib/module/3-override-tasks/build.mill

@@ -2,7 +2,7 @@ package build
 import mill._, pythonlib._
 
 object foo extends PythonModule {
-  def sources = Task.Sources {
+  def sources = Task {
     val destPath = Task.dest / "src"
     os.makeDir.all(destPath)
 
@@ -20,7 +20,7 @@ object foo extends PythonModule {
     Seq(PathRef(destPath))
   }
 
-  def mainScript = Task.Source { sources().head.path / "foo.py" }
+  def mainScript = Task { PathRef(sources().head.path / "foo.py") }
 
   def typeCheck = Task {
     println("Type Checking...")
@@ -53,7 +53,7 @@ object foo2 extends PythonModule {
     Seq(PathRef(destPath))
   }
 
-  def mainScript = Task.Source { generatedSources().head.path / "foo.py" }
+  def mainScript = Task { PathRef(generatedSources().head.path / "foo.py") }
 
 }
 
@@ -64,7 +64,7 @@ object foo3 extends PythonModule {
     os.write(destPath / "foo.py", """...""")
     super.sources() ++ Seq(PathRef(destPath))
   }
-  def mainScript = Task.Source { sources().head.path / "foo.py" }
+  def mainScript = Task { PathRef(sources().head.path / "foo.py") }
 
 }
 

scalalib/src/mill/scalalib/JavaModule.scala

@@ -919,7 +919,7 @@ trait JavaModule
    * Typically, includes the source files to generate documentation from.
    * @see [[docResources]]
    */
-  def docSources: T[Seq[PathRef]] = Task.Sources(allSources())
+  def docSources: T[Seq[PathRef]] = Task { allSources() }
 
   /**
    * Extra directories to be copied into the documentation.

scalalib/src/mill/scalalib/ScalaModule.scala

@@ -308,7 +308,7 @@ trait ScalaModule extends JavaModule with TestModule.ScalaModuleBase { outer =>
       }
     }
 
-  override def docSources: T[Seq[PathRef]] = Task.Sources {
+  override def docSources: T[Seq[PathRef]] = Task {
     if (
       ZincWorkerUtil.isScala3(scalaVersion()) && !ZincWorkerUtil.isScala3Milestone(scalaVersion())
     ) Seq(compile().classes)