Fix the scala-library dependency for (generic) platform modules (#2739)

In Scala 3 modules, that also define a platform, the scala3-library is
not correctly resolved.
The current implementation exists merely as a convenience for JS and
Native modules. `ScalaNativeModule` already handles a correct scala
library by overriding `scalaLibraryIvyDeps`. This pull request overrides
the same in `ScalaJSModule` and removed the faulty platfrom dependency
from `ScalaModule`.

E.g. imagine, someone tries to build a Mill plugin with Scala 3 (which
is currently not supported) and sets the platform to `_mill0.11`, then
you would run into the following issue:

```scala
object root extends ScalaModule {
  override def scalaVersion = "3.3.0"
  override def platformSuffix = "_mill0.11"
  // ..
}
```

```
>> mill ivyDepsTree
1 targets failed
resolvedIvyDeps
Resolution failed for 1 modules:
--------------------------------------------
  org.scala-lang:scala3-library_mill0.11_3:3.3.0
	not found: /Users/me/ivy2/local/org.scala-lang/scala3-library_mill0.11_3/3.3.0/ivys/ivy.xml
	not found: https://repo1.maven.org/maven2/org/scala-lang/scala3-library_mill0.11_3/3.3.0/scala3-library_mill0.11_3-3.3.0.pom
```

Pull request: #2739

build.sc

@@ -364,14 +364,16 @@ trait MillPublishScalaModule extends MillScalaModule with MillPublishJavaModule
 /** Publishable module which contains strictly handled API. */
 trait MillStableScalaModule extends MillPublishScalaModule with Mima {
   import com.github.lolgab.mill.mima._
-  // MIMA doesn't properly ignore things which are nested inside other private things
-  // so we have to put explicit ignores here (https://github.com/lightbend/mima/issues/771)
   override def mimaBinaryIssueFilters: T[Seq[ProblemFilter]] = Seq(
+    // MIMA doesn't properly ignore things which are nested inside other private things
+    // so we have to put explicit ignores here (https://github.com/lightbend/mima/issues/771)
     ProblemFilter.exclude[Problem]("mill.eval.ProfileLogger*"),
     ProblemFilter.exclude[Problem]("mill.eval.GroupEvaluator*"),
     ProblemFilter.exclude[Problem]("mill.eval.Tarjans*"),
     ProblemFilter.exclude[Problem]("mill.define.Ctx#Impl*"),
-    ProblemFilter.exclude[Problem]("mill.resolve.ResolveNotFoundHandler*")
+    ProblemFilter.exclude[Problem]("mill.resolve.ResolveNotFoundHandler*"),
+    // See https://github.com/com-lihaoyi/mill/pull/2739
+    ProblemFilter.exclude[ReversedMissingMethodProblem]("mill.scalajslib.ScalaJSModule.mill$scalajslib$ScalaJSModule$$super$scalaLibraryIvyDeps")
   )
   def mimaPreviousVersions: T[Seq[String]] = Settings.mimaBaseVersions
 

scalajslib/src/mill/scalajslib/ScalaJSModule.scala

@@ -5,7 +5,7 @@ import mainargs.Flag
 import mill.api.{Loose, PathRef, Result, internal}
 import mill.scalalib.api.ZincWorkerUtil
 import mill.scalalib.Lib.resolveDependencies
-import mill.scalalib.{Dep, DepSyntax, Lib, TestModule}
+import mill.scalalib.{CrossVersion, Dep, DepSyntax, Lib, TestModule}
 import mill.testrunner.{TestResult, TestRunner, TestRunnerUtils}
 import mill.define.{Command, Target, Task}
 import mill.scalajslib.api._
@@ -34,6 +34,20 @@ trait ScalaJSModule extends scalalib.ScalaModule { outer =>
 
   def scalaJSWorkerVersion = T { ZincWorkerUtil.scalaJSWorkerVersion(scalaJSVersion()) }
 
+  override def scalaLibraryIvyDeps = T {
+    val deps = super.scalaLibraryIvyDeps()
+    if (ZincWorkerUtil.isScala3(scalaVersion())) {
+      // Since Dotty/Scala3, Scala.JS is published with a platform suffix
+      deps.map(dep =>
+        dep.copy(cross = dep.cross match {
+          case c: CrossVersion.Constant => c.copy(platformed = true)
+          case c: CrossVersion.Binary => c.copy(platformed = true)
+          case c: CrossVersion.Full => c.copy(platformed = true)
+        })
+      )
+    } else deps
+  }
+
   def scalaJSWorkerClasspath = T {
     mill.util.Util.millProjectModule(
       artifact = s"mill-scalajslib-worker-${scalaJSWorkerVersion()}",

scalalib/src/mill/scalalib/Dep.scala

@@ -181,7 +181,7 @@ object CrossVersion {
     implicit def rw: RW[Full] = macroRW
   }
 
-  def empty(platformed: Boolean) = Constant(value = "", platformed)
+  def empty(platformed: Boolean): Constant = Constant(value = "", platformed)
 
   implicit def rw: RW[CrossVersion] = RW.merge(Constant.rw, Binary.rw, Full.rw)
 }

scalalib/src/mill/scalalib/Lib.scala

@@ -114,13 +114,11 @@ object Lib {
   def scalaRuntimeIvyDeps(scalaOrganization: String, scalaVersion: String): Loose.Agg[Dep] =
     if (ZincWorkerUtil.isDotty(scalaVersion)) {
       Agg(
-        // note that dotty-library has a binary version suffix, hence the :: is necessary here
         ivy"$scalaOrganization::dotty-library:$scalaVersion".forceVersion()
       )
     } else if (ZincWorkerUtil.isScala3(scalaVersion))
       Agg(
-        // note that dotty-library has a binary version suffix, hence the :: is necessary here
-        ivy"$scalaOrganization::scala3-library::$scalaVersion".forceVersion()
+        ivy"$scalaOrganization::scala3-library:$scalaVersion".forceVersion()
       )
     else
       Agg(