Fix launchIDE in the Dotty build after the full bootstrap

- Make sure that when the `excludeFromIDE` sbt-dotty plugin setting is
  on in a project, we don't try to run any non-trivial task in that
  project.

- Add all non-bootstrapped projects to `excludeFromIDE`, we always want
  to run the IDE with a bootstrapped compiler in the Dotty build. We did
  not need to do this before the full bootstrap because the
  non-bootstrapped projects were automatically excluded since they were
  Scala 2 projects.

Author: smarter

project/Build.scala

@@ -189,7 +189,8 @@ object Build {
     // Do not append Scala versions to the generated artifacts
     crossPaths := false,
     // Do not depend on the Scala library
-    autoScalaLibrary := false
+    autoScalaLibrary := false,
+    excludeFromIDE := true
   )
 
   // Settings used when compiling dotty (both non-boostrapped and bootstrapped)
@@ -203,7 +204,8 @@ object Build {
     version := dottyNonBootstrappedVersion,
     scalaVersion := referenceVersion,
     // To be removed once we stop cross-compiling with Scala 2
-    crossScalaVersions := Seq(referenceVersion, scalacVersion)
+    crossScalaVersions := Seq(referenceVersion, scalacVersion),
+    excludeFromIDE := true
   )
 
   // Settings used when compiling dotty with a non-bootstrapped dotty

sbt-dotty/src/dotty/tools/sbtplugin/DottyIDEPlugin.scala

@@ -82,16 +82,20 @@ object DottyIDEPlugin extends AutoPlugin {
 
     val (dottyVersions, dottyProjRefs) =
       structure.allProjectRefs.flatMap { projRef =>
-        val version = scalaVersion.in(projRef).get(settings).get
-        if (isDottyVersion(version))
-          Some((version, projRef))
-        else
-          crossScalaVersions.in(projRef).get(settings).get.filter(isDottyVersion).sorted.lastOption match {
-            case Some(v) =>
-              Some((v, projRef))
-            case _ =>
-              None
-          }
+        if (excludeFromIDE.in(projRef).get(settings) == Some(true))
+          None
+        else {
+          val version = scalaVersion.in(projRef).get(settings).get
+          if (isDottyVersion(version))
+            Some((version, projRef))
+          else
+            crossScalaVersions.in(projRef).get(settings).get.filter(isDottyVersion).sorted.lastOption match {
+              case Some(v) =>
+                Some((v, projRef))
+              case _ =>
+                None
+            }
+        }
       }.unzip
 
     if (dottyVersions.isEmpty)