Merge pull request #3714 from Gedochao/maintenance/debug-negative-compilation-test

Fix flaky `build-macros[_].test.testNegativeCompilation`

Author: Gedochao

.github/workflows/ci.yml

@@ -39,6 +39,8 @@ jobs:
         retention-days: 2
     - name: Cross compile everything
       run: ./mill -i '__[_].compile'
+    - name: Build macros negative compilation tests
+      run: ./mill -i build-macros[_].test.testNegativeCompilation
     - name: Unit tests
       run: ./mill -i unitTests
     - name: Convert Mill test reports to JUnit XML format

build.mill.scala

@@ -309,19 +309,11 @@ trait BuildMacros extends ScalaCliCrossSbtModule
   }
 
   object test extends ScalaCliTests {
-
-    // Is there a better way to add task dependency to test?
-    def test(args: String*): Command[(String, Seq[TestResult])] = Task.Command {
-      val res = super.test(args: _*)()
-      testNegativeCompilation()()
-      res
-    }
-
     def scalacOptions: Target[Seq[String]] = Task {
       super.scalacOptions() ++ asyncScalacOptions(scalaVersion())
     }
 
-    def testNegativeCompilation(): Command[Unit] = Task.Command {
+    def testNegativeCompilation(): Command[Unit] = Task.Command(exclusive = true) {
       val base          = Task.workspace / "modules" / "build-macros" / "src"
       val negativeTests = Seq(
         "MismatchedLeft.scala" -> Seq(
@@ -331,8 +323,11 @@ trait BuildMacros extends ScalaCliCrossSbtModule
         )
       )
 
-      val cpsSource = base / "main" / "scala" / "scala" / "build" / "EitherCps.scala"
-      assert(os.exists(cpsSource))
+      val cpsSource       = base / "main" / "scala" / "scala" / "build" / "EitherCps.scala"
+      val cpsSourceExists = os.exists(cpsSource)
+      if (!cpsSourceExists) System.err.println(s"Expected source file $cpsSource does not exist")
+      else System.err.println(s"Found source file $cpsSource")
+      assert(cpsSourceExists)
 
       val sv                                             = scalaVersion()
       def compile(extraSources: os.Path*): CommandResult =
@@ -341,7 +336,14 @@ trait BuildMacros extends ScalaCliCrossSbtModule
           mergeErrIntoOut = true,
           cwd = Task.workspace
         )
-      assert(0 == compile().exitCode)
+      val compileResult = compile()
+      if (compileResult.exitCode != 0) {
+        System.err.println(s"Compilation failed: $cpsSource")
+        System.err.println(compileResult.out.text())
+      }
+      else
+        System.err.println(s"Compiled $cpsSource successfully")
+      assert(0 == compileResult.exitCode)
 
       val notPassed = negativeTests.filter { case (testName, expectedErrors) =>
         val testFile = base / "negative-tests" / testName