Collapse skipped frames

metals/src/main/scala/scala/meta/internal/metals/debug/ClientConfigurationAdapter.scala

@@ -2,10 +2,14 @@ package scala.meta.internal.metals.debug
 
 import java.nio.file.Paths
 
+import scala.util.control.NonFatal
+
 import scala.meta.internal.metals.MetalsEnrichments._
 import scala.meta.internal.metals.SourceMapper
 import scala.meta.io.AbsolutePath
 
+import com.google.gson.JsonObject
+import com.google.gson.JsonPrimitive
 import org.eclipse.lsp4j.Position
 import org.eclipse.lsp4j.debug.InitializeRequestArguments
 import org.eclipse.lsp4j.debug.InitializeRequestArgumentsPathFormat
@@ -19,6 +23,7 @@ import org.eclipse.lsp4j.debug.SourceBreakpoint
  * @param linesStartAt1  true if client line numbers start at 1
  */
 private[debug] final case class ClientConfigurationAdapter(
+    clientId: Option[String],
     pathFormat: String,
     val linesStartAt1: Boolean,
     sourceMapper: SourceMapper,
@@ -35,6 +40,38 @@ private[debug] final case class ClientConfigurationAdapter(
     sourceMapper.mappedLineForClient(path, adaptedLine)
   }
 
+  /**
+   * In the DAP specification, the presentationHint of a StackFrame can be
+   * 'normal', 'label' or 'subtle'. Most DAP implementations use 'subtle' to
+   * indicate that a frame is skipped by the debugger. The problem is that
+   * VSCode does not collapse 'subtle' frames, as other DAP clients do.
+   * Instead it collapses 'deemphasize' frames, even if it is not part of the
+   * spec.
+   *
+   * See https://github.com/microsoft/vscode/issues/206801
+   */
+  def adaptStackTraceResponse(result: JsonObject): JsonObject = {
+    if (clientId.contains("vscode")) {
+      try {
+        // For VSCode only, we hack the json result of the stack trace response
+        // to replace all occurrences of 'subtle' by 'deemphasize'.
+        val frames = result.get("stackFrames").getAsJsonArray()
+        for (i <- 0.until(frames.size)) {
+          val frame = frames.get(i).getAsJsonObject()
+          val presentationHint = Option(frame.get("presentationHint"))
+            .map(_.getAsJsonPrimitive.getAsString)
+          if (presentationHint.contains("subtle")) {
+            frame.add("presentationHint", new JsonPrimitive("deemphasize"))
+          }
+        }
+      } catch {
+        case NonFatal(t) =>
+          scribe.error("unexpected error when adapting stack trace response", t)
+      }
+    }
+    result
+  }
+
   def toLspPosition(breakpoint: SourceBreakpoint): Position = {
     val line = breakpoint.getLine
     // LSP Position is 0-based
@@ -79,6 +116,7 @@ private[debug] object ClientConfigurationAdapter {
 
   def default(sourceMapper: SourceMapper): ClientConfigurationAdapter = {
     ClientConfigurationAdapter(
+      None,
       defautlPathFormat,
       defaultLinesStartAt1,
       sourceMapper,
@@ -95,6 +133,7 @@ private[debug] object ClientConfigurationAdapter {
       .map(_.booleanValue)
       .getOrElse(defaultLinesStartAt1)
     ClientConfigurationAdapter(
+      Option(initRequest.getClientID),
       pathFormat,
       linesStartAt1,
       sourceMapper,

metals/src/main/scala/scala/meta/internal/metals/debug/DebugProtocol.scala

@@ -29,7 +29,7 @@ import org.eclipse.lsp4j.{debug => dap}
 import org.eclipse.{lsp4j => l}
 
 object DebugProtocol {
-  import scala.meta.internal.metals.debug.DapJsonParser._
+  import DapJsonParser._
   val FirstMessageId = 1
 
   val serverName = "dap-server"

metals/src/main/scala/scala/meta/internal/metals/debug/DebugProxy.scala

@@ -239,7 +239,7 @@ private[debug] final class DebugProxy(
     // output window gets refreshed resulting in stale messages being printed on top, before
     // any actual logs from the restarted process
     case response @ DebugProtocol.StackTraceResponse(args) =>
-      import scala.meta.internal.metals.JsonParser._
+      import DapJsonParser._
       for {
         stackFrame <- args.getStackFrames
         frameSource <- Option(stackFrame.getSource)
@@ -256,7 +256,8 @@ private[debug] final class DebugProxy(
           mappedSourcePath
         )
       } frameSource.setPath(clientAdapter.adaptPathForClient(metalsSource))
-      response.setResult(args.toJson)
+      val result = clientAdapter.adaptStackTraceResponse(args.toJsonObject)
+      response.setResult(result)
       for (frame <- args.getStackFrames()) {
         frameIdToFrame.put(frame.getId, frame)
       }