[dds/dap] Handle sentinel values in Scopes and Variables requests

Fixes #51916.

Change-Id: I72f02c640084059af5e2b761554ee6ec706f5f6a
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/292540
Commit-Queue: Ben Konyi <[email protected]>
Reviewed-by: Ben Konyi <[email protected]>

Author: DanTup

pkg/dds/CHANGELOG.md

@@ -1,3 +1,6 @@
+# 2.7.8
+- [DAP] Sentinel values (such as uninitialized fields/locals) will no longer cause `scopesRequest`/`variablesRequest` to fail, instead showing appropriate text (like "<not initialized>") against the variable.
+
 # 2.7.7
 - [DAP] Debug adapters now only call `setLibraryDebuggable` when the debuggable flag changes from the default/current values, reducing the amount of VM Service traffic for new isolates/reloads.
 - [DAP] `breakpoint` events are no longer sometimes sent prior to the response to the `setBreakpointsRequest` that created them.

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

@@ -1749,7 +1749,10 @@ abstract class DartDebugAdapter<TL extends LaunchRequestArguments,
         Future<Variable> convert(int index, vm.BoundVariable variable) {
           // Store the expression that gets this object as we may need it to
           // compute evaluateNames for child objects later.
-          storeEvaluateName(variable.value, variable.name);
+          final value = variable.value;
+          if (value is vm.InstanceRef) {
+            storeEvaluateName(value, variable.name);
+          }
           return _converter.convertVmResponseToVariable(
             thread,
             variable.value,

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

@@ -239,8 +239,9 @@ class ProtocolConverter {
           final fieldEvaluateName = name != null
               ? _adapter.combineEvaluateName(evaluateName, '.$name')
               : null;
-          if (fieldEvaluateName != null) {
-            _adapter.storeEvaluateName(field.value, fieldEvaluateName);
+          final value = field.value;
+          if (fieldEvaluateName != null && value is vm.InstanceRef) {
+            _adapter.storeEvaluateName(value, fieldEvaluateName);
           }
           return convertVmResponseToVariable(
             thread,

pkg/dds/pubspec.yaml

@@ -1,5 +1,5 @@
 name: dds
-version: 2.7.7
+version: 2.7.8
 description: >-
   A library used to spawn the Dart Developer Service, used to communicate with
   a Dart VM Service instance.

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

@@ -710,6 +710,48 @@ void main() {
       );
     });
 
+    test('handles sentinel fields', () async {
+      final client = dap.client;
+      final testFile = dap.createTestFile('''
+class Foo {
+  late String foo;
+}
+
+void main() {
+  final myVariable = Foo();
+  print('Hello!'); $breakpointMarker
+}
+    ''');
+
+      final breakpointLine = lineWith(testFile, breakpointMarker);
+      final stop = await client.hitBreakpoint(testFile, breakpointLine);
+
+      await client.expectLocalVariable(
+        stop.threadId!,
+        expectedName: 'myVariable',
+        expectedDisplayString: 'Foo',
+        expectedVariables: 'foo: <not initialized>',
+      );
+    });
+
+    test('handles sentinel locals', () async {
+      final client = dap.client;
+      final testFile = dap.createTestFile('''
+void main() {
+  late String foo;
+  print('Hello!'); $breakpointMarker
+}
+    ''');
+      final breakpointLine = lineWith(testFile, breakpointMarker);
+      final stop = await client.hitBreakpoint(testFile, breakpointLine);
+
+      await client.expectScopeVariables(
+        stop.threadId!,
+        'Locals',
+        'foo: <not initialized>',
+      );
+    });
+
     group('inspect()', () {
       /// Helper to test `inspect()` with varying expressions.
       void checkInspect(