Don't fetch range if the object has no length (#1453)

Author: elliette

dwds/CHANGELOG.md

@@ -13,6 +13,7 @@
 
 - Fix chrome detection in iPhone emulation mode in chrome or edge browsers.
 - Reliably find unused port for extension backend http service.
+- Ignore offset / count parameters in getObject if the object has no length
 
 ## 11.4.0
 

dwds/lib/src/debugging/debugger.dart

@@ -362,6 +362,8 @@ class Debugger extends Domain {
   /// List/Map and [offset] and [count] should indicate the desired range.
   Future<RemoteObject> _subrange(
       String id, int offset, int count, int length) async {
+    assert(offset != null);
+    assert(length != null);
     // TODO(#809): Sometimes we already know the type of the object, and
     // we could take advantage of that to short-circuit.
     var receiver = remoteObjectFor(id);
@@ -395,12 +397,11 @@ class Debugger extends Domain {
   /// Note that the property names are JS names, e.g.
   /// Symbol(DartClass.actualName) and will need to be converted. For a system
   /// List or Map, [offset] and/or [count] can be provided to indicate a desired
-  /// range of entries. If those are provided, then [length] should also be
-  /// provided to indicate the total length of the List/Map.
+  /// range of entries. They will be ignored if there is no [length].
   Future<List<Property>> getProperties(String objectId,
       {int offset, int count, int length}) async {
     var rangeId = objectId;
-    if (offset != null || count != null) {
+    if (length != null && (offset != null || count != null)) {
       var range = await _subrange(objectId, offset ?? 0, count, length);
       rangeId = range.objectId;
     }

dwds/test/chrome_proxy_service_test.dart

@@ -492,28 +492,6 @@ void main() {
         expect(world.valueAsString, 'world');
       });
 
-      test('Strings with offset', () async {
-        var worldRef = await service.evaluate(
-            isolate.id, bootstrap.id, "helloString('world')") as InstanceRef;
-        var world = await service.getObject(isolate.id, worldRef.id,
-            count: 2, offset: 1) as Instance;
-        expect(world.valueAsString, 'or');
-        expect(world.count, 2);
-        expect(world.length, 5);
-        expect(world.offset, 1);
-      });
-
-      test('Strings with offset off the end', () async {
-        var worldRef = await service.evaluate(
-            isolate.id, bootstrap.id, "helloString('world')") as InstanceRef;
-        var world = await service.getObject(isolate.id, worldRef.id,
-            count: 5, offset: 3) as Instance;
-        expect(world.valueAsString, 'ld');
-        expect(world.count, 2);
-        expect(world.length, 5);
-        expect(world.offset, 3);
-      });
-
       test('Large strings not truncated', () async {
         var largeString = await service.evaluate(
                 isolate.id, bootstrap.id, "helloString('${'abcde' * 250}')")
@@ -564,30 +542,6 @@ void main() {
         expect(sixth.valueAsString, '5');
       });
 
-      test('Lists with count/offset', () async {
-        var list = await createList();
-        var inst = await service.getObject(isolate.id, list.objectId,
-            count: 7, offset: 4) as Instance;
-        expect(inst.length, 1001);
-        expect(inst.offset, 4);
-        expect(inst.count, 7);
-        var fifth = inst.elements[0] as InstanceRef;
-        expect(fifth.valueAsString, '100');
-        var sixth = inst.elements[1] as InstanceRef;
-        expect(sixth.valueAsString, '5');
-      });
-
-      test('Lists running off the end', () async {
-        var list = await createList();
-        var inst = await service.getObject(isolate.id, list.objectId,
-            count: 5, offset: 1000) as Instance;
-        expect(inst.length, 1001);
-        expect(inst.offset, 1000);
-        expect(inst.count, 1);
-        var only = inst.elements[0] as InstanceRef;
-        expect(only.valueAsString, '5');
-      });
-
       test('Maps', () async {
         var map = await createMap();
         var inst =
@@ -603,33 +557,6 @@ void main() {
         expect(sixth.value.valueAsString, '995');
       });
 
-      test('Maps with count/offset', () async {
-        var map = await createMap();
-        var inst = await service.getObject(isolate.id, map.objectId,
-            count: 7, offset: 4) as Instance;
-        expect(inst.length, 1001);
-        expect(inst.offset, 4);
-        expect(inst.count, 7);
-        var fifth = inst.associations[0];
-        expect(fifth.key.valueAsString, '4');
-        expect(fifth.value.valueAsString, '996');
-        var sixth = inst.associations[1];
-        expect(sixth.key.valueAsString, '5');
-        expect(sixth.value.valueAsString, '995');
-      });
-
-      test('Maps running off the end', () async {
-        var map = await createMap();
-        var inst = await service.getObject(isolate.id, map.objectId,
-            count: 5, offset: 1000) as Instance;
-        expect(inst.length, 1001);
-        expect(inst.offset, 1000);
-        expect(inst.count, 1);
-        var only = inst.associations[0];
-        expect(only.key.valueAsString, '1000');
-        expect(only.value.valueAsString, '0');
-      });
-
       test('bool', () async {
         var ref = await service.evaluate(
             isolate.id, bootstrap.id, 'helloBool(true)') as InstanceRef;
@@ -671,6 +598,190 @@ void main() {
           expect(script.tokenPosTable, isNotEmpty);
         }
       });
+
+      group('getObject called with offset/count parameters', () {
+        test('Lists with offset/count are truncated', () async {
+          var list = await createList();
+          var inst = await service.getObject(
+            isolate.id,
+            list.objectId,
+            count: 7,
+            offset: 4,
+          ) as Instance;
+          expect(inst.length, 1001);
+          expect(inst.offset, 4);
+          expect(inst.count, 7);
+          var fifth = inst.elements[0] as InstanceRef;
+          expect(fifth.valueAsString, '100');
+          var sixth = inst.elements[1] as InstanceRef;
+          expect(sixth.valueAsString, '5');
+        });
+
+        test('Lists are truncated to the end if offset/count runs off the end',
+            () async {
+          var list = await createList();
+          var inst = await service.getObject(
+            isolate.id,
+            list.objectId,
+            count: 5,
+            offset: 1000,
+          ) as Instance;
+          expect(inst.length, 1001);
+          expect(inst.offset, 1000);
+          expect(inst.count, 1);
+          var only = inst.elements[0] as InstanceRef;
+          expect(only.valueAsString, '5');
+        });
+
+        test('Maps with offset/count are truncated', () async {
+          var map = await createMap();
+          var inst = await service.getObject(
+            isolate.id,
+            map.objectId,
+            count: 7,
+            offset: 4,
+          ) as Instance;
+          expect(inst.length, 1001);
+          expect(inst.offset, 4);
+          expect(inst.count, 7);
+          var fifth = inst.associations[0];
+          expect(fifth.key.valueAsString, '4');
+          expect(fifth.value.valueAsString, '996');
+          var sixth = inst.associations[1];
+          expect(sixth.key.valueAsString, '5');
+          expect(sixth.value.valueAsString, '995');
+        });
+
+        test('Maps are truncated to the end if offset/count runs off the end',
+            () async {
+          var map = await createMap();
+          var inst = await service.getObject(
+            isolate.id,
+            map.objectId,
+            count: 5,
+            offset: 1000,
+          ) as Instance;
+          expect(inst.length, 1001);
+          expect(inst.offset, 1000);
+          expect(inst.count, 1);
+          var only = inst.associations[0];
+          expect(only.key.valueAsString, '1000');
+          expect(only.value.valueAsString, '0');
+        });
+
+        test('Strings with offset/count are truncated', () async {
+          var worldRef = await service.evaluate(
+              isolate.id, bootstrap.id, "helloString('world')") as InstanceRef;
+          var world = await service.getObject(
+            isolate.id,
+            worldRef.id,
+            count: 2,
+            offset: 1,
+          ) as Instance;
+          expect(world.valueAsString, 'or');
+          expect(world.count, 2);
+          expect(world.length, 5);
+          expect(world.offset, 1);
+        });
+
+        test(
+            'Strings are truncated to the end if offset/count runs off the end',
+            () async {
+          var worldRef = await service.evaluate(
+              isolate.id, bootstrap.id, "helloString('world')") as InstanceRef;
+          var world = await service.getObject(
+            isolate.id,
+            worldRef.id,
+            count: 5,
+            offset: 3,
+          ) as Instance;
+          expect(world.valueAsString, 'ld');
+          expect(world.count, 2);
+          expect(world.length, 5);
+          expect(world.offset, 3);
+        });
+
+        test('offset/count parameters are ignored for Classes', () async {
+          var testClass = await service.getObject(
+            isolate.id,
+            rootLibrary.classes.first.id,
+            offset: 100,
+            count: 100,
+          ) as Class;
+          expect(
+              testClass.functions,
+              unorderedEquals([
+                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),
+              ]));
+        });
+
+        test('offset/count parameters are ignored for bools', () async {
+          var ref = await service.evaluate(
+              isolate.id, bootstrap.id, 'helloBool(true)') as InstanceRef;
+          var obj = await service.getObject(
+            isolate.id,
+            ref.id,
+            offset: 100,
+            count: 100,
+          ) as Instance;
+          expect(obj.kind, InstanceKind.kBool);
+          expect(obj.classRef.name, 'Bool');
+          expect(obj.valueAsString, 'true');
+        });
+
+        test('offset/count parameters are ignored for nums', () async {
+          var ref = await service.evaluate(
+              isolate.id, bootstrap.id, 'helloNum(42)') as InstanceRef;
+          var obj = await service.getObject(
+            isolate.id,
+            ref.id,
+            offset: 100,
+            count: 100,
+          ) as Instance;
+          expect(obj.kind, InstanceKind.kDouble);
+          expect(obj.classRef.name, 'Double');
+          expect(obj.valueAsString, '42');
+        });
+
+        test('offset/count parameters are ignored for null', () async {
+          var ref = await service.evaluate(
+              isolate.id, bootstrap.id, 'helloNum(null)') as InstanceRef;
+          var obj = await service.getObject(
+            isolate.id,
+            ref.id,
+            offset: 100,
+            count: 100,
+          ) as Instance;
+          expect(obj.kind, InstanceKind.kNull);
+          expect(obj.classRef.name, 'Null');
+          expect(obj.valueAsString, 'null');
+        });
+      });
     });
 
     test('getScripts', () async {