[dds/dap] Improve display of Sets in debug views

- Show "Set (x items)" to match lists and maps
- Compute an evaluation name as "x.elementAt(y)" since "x[y]" isn't valid for sets

Fixes #60488

Change-Id: Ifb9df6e1d7cf91e2e25a421565d4c5fbb75ca0fc
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/420704
Reviewed-by: Derek Xu <[email protected]>
Reviewed-by: Ben Konyi <[email protected]>
Commit-Queue: Ben Konyi <[email protected]>

Author: DanTup

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

@@ -102,10 +102,12 @@ class ProtocolConverter {
         }
       }
       return stringValue;
-    } else if (_isList(ref)) {
+    } else if (ref.isList) {
       return '${ref.kind} (${ref.length} ${ref.length == 1 ? "item" : "items"})';
-    } else if (_isMap(ref)) {
+    } else if (ref.isMap) {
       return 'Map (${ref.length} ${ref.length == 1 ? "item" : "items"})';
+    } else if (ref.isSet) {
+      return 'Set (${ref.length} ${ref.length == 1 ? "item" : "items"})';
     } else if (ref.kind == 'Type') {
       return 'Type (${ref.name})';
     } else {
@@ -145,14 +147,17 @@ class ProtocolConverter {
         )
       ];
     } else if (elements != null) {
-      // For lists, map each item (in the requested subset) to a variable.
+      // For lists and sets, map each item (in the requested subset) to a
+      // variable.
       // Elements can contain nulls!
       final start = startItem ?? 0;
       return Future.wait(elements.cast<vm.Response?>().mapIndexed(
         (index, response) {
           final name = '[${start + index}]';
+          final nameForEvaluation =
+              instance.isSet ? '.elementAt(${start + index})' : name;
           final itemEvaluateName =
-              _adapter.combineEvaluateName(evaluateName, name);
+              _adapter.combineEvaluateName(evaluateName, nameForEvaluation);
           if (response is vm.InstanceRef) {
             _adapter.storeEvaluateName(response, itemEvaluateName);
           }
@@ -209,7 +214,7 @@ class ProtocolConverter {
           variablesReference: thread.storeData(VariableData(mapEntry, format)),
         );
       }));
-    } else if (_isList(instance) &&
+    } else if (instance.isList &&
         instance.length != null &&
         instance.bytes != null) {
       final formatter = format ?? const VariableFormat();
@@ -518,7 +523,8 @@ class ProtocolConverter {
           allowCallingToString: allowCallingToString,
           format: format,
         ),
-        indexedVariables: _isList(response) ? response.length : null,
+        indexedVariables:
+            response.isList || response.isSet ? response.length : null,
         variablesReference: variablesReference,
       );
     } else if (response is vm.Sentinel) {
@@ -550,15 +556,6 @@ class ProtocolConverter {
     }
   }
 
-  /// Returns whether [ref] is a List kind.
-  ///
-  /// This includes standard Dart [List], as well as lists from
-  /// `dart:typed_data` such as `Uint8List`.
-  bool _isList(vm.InstanceRef ref) => ref.kind?.endsWith('List') ?? false;
-
-  /// Returns whether [ref] is a Map kind.
-  bool _isMap(vm.InstanceRef ref) => ref.kind == 'Map';
-
   /// Converts a VM Service stack frame to a DAP stack frame.
   Future<dap.StackFrame> convertVmToDapStackFrame(
     ThreadInfo thread,
@@ -820,3 +817,17 @@ class ProtocolConverter {
     return null;
   }
 }
+
+extension on vm.InstanceRef {
+  /// Whether this instance is a List kind.
+  ///
+  /// This includes standard Dart [List], as well as lists from
+  /// `dart:typed_data` such as `Uint8List`.
+  bool get isList => kind?.endsWith('List') ?? false;
+
+  /// Whether this instance is a Map kind.
+  bool get isMap => kind == 'Map';
+
+  /// Whether this instance is a Set kind.
+  bool get isSet => kind == 'Set';
+}

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

@@ -405,6 +405,55 @@ void main(List<String> args) {
       );
     });
 
+    test('renders a simple set', () async {
+      final client = dap.client;
+      final testFile = dap.createTestFile('''
+void main(List<String> args) {
+  final myVariable = {"first", "second", "third", null};
+  print('Hello!'); $breakpointMarker
+}
+    ''');
+      final breakpointLine = lineWith(testFile, breakpointMarker);
+
+      final stop = await client.hitBreakpoint(testFile, breakpointLine);
+      await client.expectLocalVariable(
+        stop.threadId!,
+        expectedName: 'myVariable',
+        expectedDisplayString: 'Set (4 items)',
+        expectedIndexedItems: 4,
+        expectedVariables: '''
+            [0]: "first", eval: myVariable.elementAt(0)
+            [1]: "second", eval: myVariable.elementAt(1)
+            [2]: "third", eval: myVariable.elementAt(2)
+            [3]: null
+        ''',
+      );
+    });
+
+    test('renders a simple set subset', () async {
+      final client = dap.client;
+      final testFile = dap.createTestFile('''
+void main(List<String> args) {
+  final myVariable = {"first", "second", "third"};
+  print('Hello!'); $breakpointMarker
+}
+    ''');
+      final breakpointLine = lineWith(testFile, breakpointMarker);
+
+      final stop = await client.hitBreakpoint(testFile, breakpointLine);
+      await client.expectLocalVariable(
+        stop.threadId!,
+        expectedName: 'myVariable',
+        expectedDisplayString: 'Set (3 items)',
+        expectedIndexedItems: 3,
+        expectedVariables: '''
+            [1]: "second", eval: myVariable.elementAt(1)
+        ''',
+        start: 1,
+        count: 1,
+      );
+    });
+
     test('only calls toString() for 100 items in a list', () async {
       final client = dap.client;
       // Generate a file that assigns a list of 150 items