feat: queueMicrotask support (#1868)

Author: NathanWalker

test-app/app/src/main/assets/app/mainpage.js

@@ -72,4 +72,5 @@ require("./tests/testPostFrameCallback");
 require("./tests/console/logTests.js");
 require('./tests/testURLImpl.js');
 require('./tests/testURLSearchParamsImpl.js');
-require('./tests/testPerformanceNow');
+require('./tests/testPerformanceNow');
+require('./tests/testQueueMicrotask');

test-app/app/src/main/assets/app/tests/testQueueMicrotask.js

@@ -0,0 +1,35 @@
+describe('queueMicrotask', () => {
+    it('should be defined as a function', () => {
+        expect(typeof queueMicrotask).toBe('function');
+    });
+
+    it('should throw TypeError when callback is not a function', () => {
+        expect(() => queueMicrotask(null)).toThrow();
+        expect(() => queueMicrotask(123)).toThrow();
+        expect(() => queueMicrotask({})).toThrow();
+    });
+
+    it('runs after current stack but before setTimeout(0)', (done) => {
+        const order = [];
+        queueMicrotask(() => order.push('microtask'));
+        setTimeout(() => {
+            order.push('timeout');
+            expect(order).toEqual(['microtask', 'timeout']);
+            done();
+        }, 0);
+        // at this point, nothing should have run yet
+        expect(order.length).toBe(0);
+    });
+
+    it('preserves ordering with Promise microtasks', (done) => {
+        const order = [];
+        queueMicrotask(() => order.push('qm1'));
+        Promise.resolve().then(() => order.push('p'));
+        queueMicrotask(() => order.push('qm2'));
+
+        setTimeout(() => {
+            expect(order).toEqual(['qm1', 'p', 'qm2']);
+            done();
+        }, 0);
+    });
+});

test-app/runtime/src/main/cpp/Runtime.cpp

@@ -537,6 +537,21 @@ Isolate* Runtime::PrepareV8Runtime(const string& filesPath, const string& native
         performanceTemplate->Set(ArgConverter::ConvertToV8String(isolate, "timeOrigin"), Number::New(isolate, m_realtimeOrigin));
         globalTemplate->Set(ArgConverter::ConvertToV8String(isolate, "performance"), performanceTemplate);
     }
+    // queueMicrotask(callback) per spec: https://developer.mozilla.org/en-US/docs/Web/API/Window/queueMicrotask
+    globalTemplate->Set(
+        ArgConverter::ConvertToV8String(isolate, "queueMicrotask"),
+        FunctionTemplate::New(
+            isolate,
+            [](const v8::FunctionCallbackInfo<v8::Value>& info) {
+                auto* isolate = info.GetIsolate();
+                if (info.Length() < 1 || !info[0]->IsFunction()) {
+                    isolate->ThrowException(v8::Exception::TypeError(
+                        ArgConverter::ConvertToV8String(isolate, "queueMicrotask: callback must be a function")));
+                    return;
+                }
+                v8::Local<v8::Function> cb = info[0].As<v8::Function>();
+                isolate->EnqueueMicrotask(cb);
+            }));
     globalTemplate->Set(ArgConverter::ConvertToV8String(isolate, "__releaseNativeCounterpart"), FunctionTemplate::New(isolate, CallbackHandlers::ReleaseNativeCounterpartCallback));
     globalTemplate->Set(ArgConverter::ConvertToV8String(isolate, "__markingMode"), Number::New(isolate, m_objectManager->GetMarkingMode()), readOnlyFlags);
     globalTemplate->Set(ArgConverter::ConvertToV8String(isolate, "__runOnMainThread"), FunctionTemplate::New(isolate, CallbackHandlers::RunOnMainThreadCallback));