[dds] Add support for DAP sourceRequest to download source from the VM

Change-Id: Icb639c7008d51d6ffbecb95e362cc07c81993424
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/209103
Reviewed-by: Ben Konyi <bkonyi@google.com>
Commit-Queue: Ben Konyi <bkonyi@google.com>

pkg/dds/lib/src/dap/adapters/dart.dart

@@ -21,6 +21,14 @@ import '../protocol_converter.dart';
 import '../protocol_generated.dart';
 import '../protocol_stream.dart';
 
+/// The mime type to send with source responses to the client.
+///
+/// This is used so if the source name does not end with ".dart" the client can
+/// still tell which language to use (for syntax highlighting, etc.).
+///
+/// https://github.com/microsoft/vscode/issues/8182#issuecomment-231151640
+const dartMimeType = 'text/x-dart';
+
 /// Maximum number of toString()s to be called when responding to variables
 /// requests from the client.
 ///
@@ -723,6 +731,44 @@ abstract class DartDebugAdapter<T extends DartLaunchRequestArguments>
     await _dds?.shutdown();
   }
 
+  /// [sourceRequest] is called by the client to request source code for a given
+  /// source.
+  ///
+  /// The client may provide a whole source or just an int sourceReference (the
+  /// spec originally had only sourceReference but now supports whole sources).
+  ///
+  /// The supplied sourceReference should correspond to a ScriptRef instance
+  /// that was stored to generate the sourceReference when sent to the client.
+  @override
+  Future<void> sourceRequest(
+    Request request,
+    SourceArguments args,
+    void Function(SourceResponseBody) sendResponse,
+  ) async {
+    final storedData = _isolateManager.getStoredData(
+      args.source?.sourceReference ?? args.sourceReference,
+    );
+    if (storedData == null) {
+      throw StateError('source reference is no longer valid');
+    }
+    final thread = storedData.thread;
+    final data = storedData.data;
+    final scriptRef = data is vm.ScriptRef ? data : null;
+    if (scriptRef == null) {
+      throw StateError('source reference was not a valid script');
+    }
+
+    final script = await thread.getScript(scriptRef);
+    final scriptSource = script.source;
+    if (scriptSource == null) {
+      throw DebugAdapterException('<source not available>');
+    }
+
+    sendResponse(
+      SourceResponseBody(content: scriptSource, mimeType: dartMimeType),
+    );
+  }
+
   /// Handles a request from the client for the call stack for [args.threadId].
   ///
   /// This is usually called after we sent a [StoppedEvent] to the client

pkg/dds/lib/src/dap/base_debug_adapter.dart

@@ -204,6 +204,12 @@ abstract class BaseDebugAdapter<TLaunchArgs extends LaunchRequestArguments> {
     void Function(SetExceptionBreakpointsResponseBody) sendResponse,
   );
 
+  Future<void> sourceRequest(
+    Request request,
+    SourceArguments args,
+    void Function(SourceResponseBody) sendResponse,
+  );
+
   Future<void> stackTraceRequest(
     Request request,
     StackTraceArguments args,
@@ -312,6 +318,8 @@ abstract class BaseDebugAdapter<TLaunchArgs extends LaunchRequestArguments> {
       handle(request, threadsRequest, _voidArgs);
     } else if (request.command == 'stackTrace') {
       handle(request, stackTraceRequest, StackTraceArguments.fromJson);
+    } else if (request.command == 'source') {
+      handle(request, sourceRequest, SourceArguments.fromJson);
     } else if (request.command == 'scopes') {
       handle(request, scopesRequest, ScopesArguments.fromJson);
     } else if (request.command == 'variables') {

pkg/dds/test/dap/integration/debug_test.dart

@@ -129,6 +129,45 @@ void main(List<String> args) async {
       final vmServiceUri = _extractVmServiceUri(outputEvents.first);
       expect(vmServiceUri.path, matches(vmServiceAuthCodePathPattern));
     });
+
+    test('can download source code from the VM', () async {
+      final client = dap.client;
+      final testFile = dap.createTestFile(simpleBreakpointProgram);
+      final breakpointLine = lineWith(testFile, '// BREAKPOINT');
+
+      // Hit the initial breakpoint.
+      final stop = await dap.client.hitBreakpoint(
+        testFile,
+        breakpointLine,
+        launch: () => client.launch(
+          testFile.path,
+          debugSdkLibraries: true,
+        ),
+      );
+
+      // Step in to go into print.
+      final responses = await Future.wait([
+        client.expectStop('step', sourceName: 'dart:core/print.dart'),
+        client.stepIn(stop.threadId!),
+      ], eagerError: true);
+      final stopResponse = responses.first as StoppedEventBody;
+
+      // Fetch the top stack frame (which should be inside print).
+      final stack = await client.getValidStack(
+        stopResponse.threadId!,
+        startFrame: 0,
+        numFrames: 1,
+      );
+      final topFrame = stack.stackFrames.first;
+
+      // SDK sources should have a sourceReference and no path.
+      expect(topFrame.source!.path, isNull);
+      expect(topFrame.source!.sourceReference, greaterThan(0));
+
+      // Source code should contain the implementation/signature of print().
+      final source = await client.getValidSource(topFrame.source!);
+      expect(source.content, contains('void print(Object? object) {'));
+    });
     // These tests can be slow due to starting up the external server process.
   }, timeout: Timeout.none);
 

pkg/dds/test/dap/integration/test_client.dart

@@ -217,6 +217,18 @@ class DapTestClient {
     _channel.sendResponse(response);
   }
 
+  /// Sends a source request to the server to request source code for a [source]
+  /// reference that may have come from a stack frame or similar.
+  ///
+  /// Returns a Future that completes when the server returns a corresponding
+  /// response.
+  Future<Response> source(Source source) => sendRequest(
+        SourceArguments(
+          source: source,
+          sourceReference: source.sourceReference!,
+        ),
+      );
+
   /// Sends a stackTrace request to the server to request the call stack for a
   /// given thread.
   ///
@@ -475,6 +487,14 @@ extension DapTestClientExtension on DapTestClient {
         response.body as Map<String, Object?>);
   }
 
+  /// Fetches source for a sourceReference and asserts it was a valid response.
+  Future<SourceResponseBody> getValidSource(Source source) async {
+    final response = await this.source(source);
+    expect(response.success, isTrue);
+    expect(response.command, equals('source'));
+    return SourceResponseBody.fromJson(response.body as Map<String, Object?>);
+  }
+
   /// Fetches threads and asserts a valid response.
   Future<ThreadsResponseBody> getValidThreads() async {
     final response = await threads();