Ignore offset / count if an instance has no length (#1972)

Author: elliette

dwds/lib/src/debugging/debugger.dart

@@ -403,15 +403,21 @@ class Debugger extends Domain {
     return null;
   }
 
-  static bool _isEmptyRange({int? offset, int? count, int? length}) {
+  static bool _isEmptyRange({
+    required int length,
+    int? offset,
+    int? count,
+  }) {
     if (count == 0) return true;
-    if (length == null) return false;
     if (offset == null) return false;
     return offset >= length;
   }
 
-  static bool _isSubRange({int? offset, int? count, int? length}) {
-    if (length == null) return false;
+  static bool _isSubRange({
+    required int length,
+    int? offset,
+    int? count,
+  }) {
     if (offset == 0 && count == null) return false;
     return offset != null || count != null;
   }
@@ -502,13 +508,16 @@ class Debugger extends Domain {
     int? length,
   }) async {
     String rangeId = objectId;
-    if (_isEmptyRange(offset: offset, count: count, length: length)) {
-      return [];
-    }
-    if (_isSubRange(offset: offset, count: count, length: length)) {
-      final range = await _subRange(objectId,
-          offset: offset ?? 0, count: count, length: length!);
-      rangeId = range.objectId ?? rangeId;
+    // Ignore offset/count if there is no length:
+    if (length != null) {
+      if (_isEmptyRange(offset: offset, count: count, length: length)) {
+        return [];
+      }
+      if (_isSubRange(offset: offset, count: count, length: length)) {
+        final range = await _subRange(objectId,
+            offset: offset ?? 0, count: count, length: length);
+        rangeId = range.objectId ?? rangeId;
+      }
     }
     final jsProperties = await sendCommandAndValidateResult<List>(
       _remoteDebugger,

dwds/test/chrome_proxy_service_test.dart

@@ -921,7 +921,9 @@ void main() {
           expect(world.offset, 3);
         });
 
-        test('offset/count parameters are ignored for Classes', () async {
+        test(
+            'offset/count parameters greater than zero are ignored for Classes',
+            () async {
           final testClass = await service.getObject(
             isolate.id!,
             rootLibrary!.classes!.first.id!,
@@ -968,6 +970,54 @@ void main() {
               ]));
         });
 
+        test('offset/count parameters equal to zero are ignored for Classes',
+            () async {
+          final testClass = await service.getObject(
+            isolate.id!,
+            rootLibrary!.classes!.first.id!,
+            offset: 0,
+            count: 0,
+          ) as Class;
+          expect(
+              testClass.functions,
+              unorderedEquals([
+                predicate(
+                    (FuncRef f) => f.name == 'staticHello' && f.isStatic!),
+                predicate((FuncRef f) => f.name == 'message' && !f.isStatic!),
+                predicate((FuncRef f) => f.name == 'notFinal' && !f.isStatic!),
+                predicate((FuncRef f) => f.name == 'hello' && !f.isStatic!),
+                predicate((FuncRef f) => f.name == '_equals' && !f.isStatic!),
+                predicate((FuncRef f) => f.name == 'hashCode' && !f.isStatic!),
+                predicate((FuncRef f) => f.name == 'toString' && !f.isStatic!),
+                predicate(
+                    (FuncRef f) => f.name == 'noSuchMethod' && !f.isStatic!),
+                predicate(
+                    (FuncRef f) => f.name == 'runtimeType' && !f.isStatic!),
+              ]));
+          expect(
+              testClass.fields,
+              unorderedEquals([
+                predicate((FieldRef f) =>
+                    f.name == 'message' &&
+                    f.declaredType != null &&
+                    !f.isStatic! &&
+                    !f.isConst! &&
+                    f.isFinal!),
+                predicate((FieldRef f) =>
+                    f.name == 'notFinal' &&
+                    f.declaredType != null &&
+                    !f.isStatic! &&
+                    !f.isConst! &&
+                    !f.isFinal!),
+                predicate((FieldRef f) =>
+                    f.name == 'staticMessage' &&
+                    f.declaredType != null &&
+                    f.isStatic! &&
+                    !f.isConst! &&
+                    !f.isFinal!),
+              ]));
+        });
+
         test('offset/count parameters are ignored for bools', () async {
           final ref = await service.evaluate(
               isolate.id!, bootstrap!.id!, 'helloBool(true)') as InstanceRef;