improve error messages when no main classes can be found

scalameta · Mar 7, 2025 · d687486 · d687486
1 parent 29a72b6
commit d687486
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Showing 2 changed files with 15 additions and 5 deletions.
diff --git a/metals/src/main/scala/scala/meta/internal/metals/WorkspaceLspService.scala b/metals/src/main/scala/scala/meta/internal/metals/WorkspaceLspService.scala
@@ -882,10 +882,20 @@ class WorkspaceLspService(
                   }
               }(_ => true)
               .flatMap { mains =>
-                mains.headOption.fold(
+                mains.fold(
                   Future.failed[DebugSessionParams](
-                    DiscoveryFailures
-                      .NoMainClassFoundException(unresolvedParams.mainClass)
+                    Option(unresolvedParams.buildTarget)
+                      .map(buildTarget =>
+                        DiscoveryFailures
+                          .ClassNotFoundInBuildTargetException(
+                            unresolvedParams.mainClass,
+                            buildTarget,
+                          )
+                      )
+                      .getOrElse(
+                        DiscoveryFailures
+                          .NoMainClassFoundException(unresolvedParams.mainClass)
+                      )
                   )
                 )(Future.successful(_))
               }

diff --git a/metals/src/main/scala/scala/meta/internal/metals/debug/DiscoveryFailures.scala b/metals/src/main/scala/scala/meta/internal/metals/debug/DiscoveryFailures.scala
@@ -21,13 +21,13 @@ object DiscoveryFailures {
       className: String,
       buildTarget: String,
   ) extends Exception(
-        s"Class '$className' not found in build target '${buildTarget}'"
+        s"Main class '$className' not found in build target '${buildTarget}' (not considering dependencies)"
       )
 
   case class NoMainClassFoundException(
       className: String
   ) extends Exception(
-        s"Class '$className' not found in any build target"
+        s"Main class '$className' not found in any build target (not considering dependencies)"
       )
 
   case class BuildTargetNotFoundForPathException(path: AbsolutePath)