LibJS: Implement %IteratorHelperPrototype%.return

Userland/Libraries/LibJS/Runtime/IteratorHelperPrototype.cpp

@@ -44,16 +44,28 @@ JS_DEFINE_NATIVE_FUNCTION(IteratorHelperPrototype::return_)
 {
     // 1. Let O be this value.
     // 2. Perform ? RequireInternalSlot(O, [[UnderlyingIterator]]).
+    auto iterator = TRY(typed_this_object(vm));
+
     // 3. Assert: O has a [[GeneratorState]] slot.
     // 4. If O.[[GeneratorState]] is suspendedStart, then
+    if (iterator->generator_state() == GeneratorObject::GeneratorState::SuspendedStart) {
         // a. Set O.[[GeneratorState]] to completed.
+        iterator->set_generator_state(GeneratorObject::GeneratorState::Completed);
+
         // b. NOTE: Once a generator enters the completed state it never leaves it and its associated execution context is never resumed. Any execution state associated with O can be discarded at this point.
+
         // c. Perform ? IteratorClose(O.[[UnderlyingIterator]], NormalCompletion(unused)).
+        TRY(iterator_close(vm, iterator->underlying_iterator(), normal_completion({})));
+
         // d. Return CreateIterResultObject(undefined, true).
+        return create_iterator_result_object(vm, js_undefined(), true);
+    }
+
     // 5. Let C be Completion { [[Type]]: return, [[Value]]: undefined, [[Target]]: empty }.
+    Completion completion { Completion::Type::Return, js_undefined(), {} };
+
     // 6. Return ? GeneratorResumeAbrupt(O, C, "Iterator Helper").
-
+    return TRY(iterator->resume_abrupt(vm, move(completion), "Iterator Helper"sv));
-    return vm.throw_completion<InternalError>(ErrorType::NotImplemented, "IteratorHelper.prototype.return"sv);
 }
 
 }

Userland/Libraries/LibJS/Tests/builtins/Iterator/Iterator.prototype.drop.js

@@ -49,6 +49,28 @@ describe("errors", () => {
             iterator.next();
         }).toThrow(TestError);
     });
+
+    test("iterator's return method throws", () => {
+        function TestError() {}
+
+        class TestIterator extends Iterator {
+            next() {
+                return {
+                    done: false,
+                    value: 1,
+                };
+            }
+
+            return() {
+                throw new TestError();
+            }
+        }
+
+        expect(() => {
+            const iterator = new TestIterator().drop(1);
+            iterator.return();
+        }).toThrow(TestError);
+    });
 });
 
 describe("normal behavior", () => {
@@ -115,4 +137,31 @@ describe("normal behavior", () => {
         expect(value.value).toBeUndefined();
         expect(value.done).toBeTrue();
     });
+
+    test("return is forwarded to the underlying iterator's return method", () => {
+        let returnCount = 0;
+
+        class TestIterator extends Iterator {
+            next() {
+                return {
+                    done: false,
+                    value: 1,
+                };
+            }
+
+            return() {
+                ++returnCount;
+                return {};
+            }
+        }
+
+        const iterator = new TestIterator().drop(1);
+        expect(returnCount).toBe(0);
+
+        iterator.return();
+        expect(returnCount).toBe(1);
+
+        iterator.return();
+        expect(returnCount).toBe(1);
+    });
 });

Userland/Libraries/LibJS/Tests/builtins/Iterator/Iterator.prototype.filter.js

@@ -40,6 +40,28 @@ describe("errors", () => {
         }).toThrow(TestError);
     });
 
+    test("iterator's return method throws", () => {
+        function TestError() {}
+
+        class TestIterator extends Iterator {
+            next() {
+                return {
+                    done: false,
+                    value: 1,
+                };
+            }
+
+            return() {
+                throw new TestError();
+            }
+        }
+
+        expect(() => {
+            const iterator = new TestIterator().filter(() => true);
+            iterator.return();
+        }).toThrow(TestError);
+    });
+
     test("predicate function throws", () => {
         function TestError() {}
 
@@ -153,4 +175,31 @@ describe("normal behavior", () => {
         expect(firstFilterCount).toBe(4);
         expect(secondFilterCount).toBe(2);
     });
+
+    test("return is forwarded to the underlying iterator's return method", () => {
+        let returnCount = 0;
+
+        class TestIterator extends Iterator {
+            next() {
+                return {
+                    done: false,
+                    value: 1,
+                };
+            }
+
+            return() {
+                ++returnCount;
+                return {};
+            }
+        }
+
+        const iterator = new TestIterator().filter(() => true);
+        expect(returnCount).toBe(0);
+
+        iterator.return();
+        expect(returnCount).toBe(1);
+
+        iterator.return();
+        expect(returnCount).toBe(1);
+    });
 });

Userland/Libraries/LibJS/Tests/builtins/Iterator/Iterator.prototype.flatMap.js

@@ -40,6 +40,28 @@ describe("errors", () => {
         }).toThrow(TestError);
     });
 
+    test("iterator's return method throws", () => {
+        function TestError() {}
+
+        class TestIterator extends Iterator {
+            next() {
+                return {
+                    done: false,
+                    value: 1,
+                };
+            }
+
+            return() {
+                throw new TestError();
+            }
+        }
+
+        expect(() => {
+            const iterator = new TestIterator().flatMap(() => 0);
+            iterator.return();
+        }).toThrow(TestError);
+    });
+
     test("mapper function throws", () => {
         function TestError() {}
 
@@ -138,4 +160,31 @@ describe("normal behavior", () => {
         expect(value.value).toBeUndefined();
         expect(value.done).toBeTrue();
     });
+
+    test("return is forwarded to the underlying iterator's return method", () => {
+        let returnCount = 0;
+
+        class TestIterator extends Iterator {
+            next() {
+                return {
+                    done: false,
+                    value: 1,
+                };
+            }
+
+            return() {
+                ++returnCount;
+                return {};
+            }
+        }
+
+        const iterator = new TestIterator().flatMap(() => 0);
+        expect(returnCount).toBe(0);
+
+        iterator.return();
+        expect(returnCount).toBe(1);
+
+        iterator.return();
+        expect(returnCount).toBe(1);
+    });
 });

Userland/Libraries/LibJS/Tests/builtins/Iterator/Iterator.prototype.map.js

@@ -40,6 +40,28 @@ describe("errors", () => {
         }).toThrow(TestError);
     });
 
+    test("iterator's return method throws", () => {
+        function TestError() {}
+
+        class TestIterator extends Iterator {
+            next() {
+                return {
+                    done: false,
+                    value: 1,
+                };
+            }
+
+            return() {
+                throw new TestError();
+            }
+        }
+
+        expect(() => {
+            const iterator = new TestIterator().map(() => 0);
+            iterator.return();
+        }).toThrow(TestError);
+    });
+
     test("mapper function throws", () => {
         function TestError() {}
 
@@ -141,4 +163,31 @@ describe("normal behavior", () => {
         expect(value.value).toBeUndefined();
         expect(value.done).toBeTrue();
     });
+
+    test("return is forwarded to the underlying iterator's return method", () => {
+        let returnCount = 0;
+
+        class TestIterator extends Iterator {
+            next() {
+                return {
+                    done: false,
+                    value: 1,
+                };
+            }
+
+            return() {
+                ++returnCount;
+                return {};
+            }
+        }
+
+        const iterator = new TestIterator().map(() => 0);
+        expect(returnCount).toBe(0);
+
+        iterator.return();
+        expect(returnCount).toBe(1);
+
+        iterator.return();
+        expect(returnCount).toBe(1);
+    });
 });

Userland/Libraries/LibJS/Tests/builtins/Iterator/Iterator.prototype.take.js

@@ -49,6 +49,28 @@ describe("errors", () => {
             iterator.next();
         }).toThrow(TestError);
     });
+
+    test("iterator's return method throws", () => {
+        function TestError() {}
+
+        class TestIterator extends Iterator {
+            next() {
+                return {
+                    done: false,
+                    value: 1,
+                };
+            }
+
+            return() {
+                throw new TestError();
+            }
+        }
+
+        expect(() => {
+            const iterator = new TestIterator().take(1);
+            iterator.return();
+        }).toThrow(TestError);
+    });
 });
 
 describe("normal behavior", () => {
@@ -120,4 +142,31 @@ describe("normal behavior", () => {
         expect(value.value).toBeUndefined();
         expect(value.done).toBeTrue();
     });
+
+    test("return is forwarded to the underlying iterator's return method", () => {
+        let returnCount = 0;
+
+        class TestIterator extends Iterator {
+            next() {
+                return {
+                    done: false,
+                    value: 1,
+                };
+            }
+
+            return() {
+                ++returnCount;
+                return {};
+            }
+        }
+
+        const iterator = new TestIterator().take(1);
+        expect(returnCount).toBe(0);
+
+        iterator.return();
+        expect(returnCount).toBe(1);
+
+        iterator.return();
+        expect(returnCount).toBe(1);
+    });
 });