Remove minSched hack for wasm

main_test.go

@@ -690,6 +690,33 @@ func TestWasmExport(t *testing.T) {
 	}
 }
 
+// Test js.FuncOf (for syscall/js).
+// This test might be extended in the future to cover more cases in syscall/js.
+func TestWasmFuncOf(t *testing.T) {
+	// Build the wasm binary.
+	tmpdir := t.TempDir()
+	options := optionsFromTarget("wasm", sema)
+	buildConfig, err := builder.NewConfig(&options)
+	if err != nil {
+		t.Fatal(err)
+	}
+	result, err := builder.Build("testdata/wasmfunc.go", ".wasm", tmpdir, buildConfig)
+	if err != nil {
+		t.Fatal("failed to build binary:", err)
+	}
+
+	// Test the resulting binary using NodeJS.
+	output := &bytes.Buffer{}
+	cmd := exec.Command("node", "testdata/wasmfunc.js", result.Binary, buildConfig.BuildMode())
+	cmd.Stdout = output
+	cmd.Stderr = output
+	err = cmd.Run()
+	if err != nil {
+		t.Error("failed to run node:", err)
+	}
+	checkOutput(t, "testdata/wasmfunc.txt", output.Bytes())
+}
+
 // Test //go:wasmexport in JavaScript (using NodeJS).
 func TestWasmExportJS(t *testing.T) {
 	type testCase struct {

src/runtime/runtime_wasm_js.go

@@ -4,13 +4,6 @@ package runtime
 
 type timeUnit float64 // time in milliseconds, just like Date.now() in JavaScript
 
-// wasmNested is used to detect scheduler nesting (WASM calls into JS calls back into WASM).
-// When this happens, we need to use a reduced version of the scheduler.
-//
-// TODO: this variable can probably be removed once //go:wasmexport is the only
-// allowed way to export a wasm function (currently, //export also works).
-var wasmNested bool
-
 var handleEvent func()
 
 //go:linkname setEventHandler syscall/js.setEventHandler

src/runtime/runtime_wasm_js_scheduler.go

@@ -8,24 +8,10 @@ func resume() {
 		handleEvent()
 	}()
 
-	if wasmNested {
-		minSched()
-		return
-	}
-
-	wasmNested = true
 	scheduler(false)
-	wasmNested = false
 }
 
 //export go_scheduler
 func go_scheduler() {
-	if wasmNested {
-		minSched()
-		return
-	}
-
-	wasmNested = true
 	scheduler(false)
-	wasmNested = false
 }

src/runtime/scheduler.go

@@ -247,24 +247,6 @@ func scheduler(returnAtDeadlock bool) {
 	}
 }
 
-// This horrible hack exists to make WASM work properly.
-// When a WASM program calls into JS which calls back into WASM, the event with which we called back in needs to be handled before returning.
-// Thus there are two copies of the scheduler running at once.
-// This is a reduced version of the scheduler which does not deal with the timer queue (that is a problem for the outer scheduler).
-func minSched() {
-	scheduleLog("start nested scheduler")
-	for !schedulerDone {
-		t := runqueue.Pop()
-		if t == nil {
-			break
-		}
-
-		scheduleLogTask("  run:", t)
-		t.Resume()
-	}
-	scheduleLog("stop nested scheduler")
-}
-
 func Gosched() {
 	runqueue.Push(task.Current())
 	task.Pause()

testdata/wasmfunc.go

@@ -0,0 +1,17 @@
+package main
+
+import "syscall/js"
+
+func main() {
+	js.Global().Call("setCallback", js.FuncOf(func(this js.Value, args []js.Value) any {
+		println("inside callback! parameters:")
+		sum := 0
+		for _, value := range args {
+			n := value.Int()
+			println("  parameter:", n)
+			sum += n
+		}
+		return sum
+	}))
+	js.Global().Call("callCallback")
+}

testdata/wasmfunc.js

@@ -0,0 +1,21 @@
+require('../targets/wasm_exec.js');
+
+var callback;
+
+global.setCallback = (cb) => {
+    callback = cb;
+};
+
+global.callCallback = () => {
+    console.log('calling callback!');
+    let result = callback(1, 2, 3, 4);
+    console.log('result from callback:', result);
+};
+
+let go = new Go();
+WebAssembly.instantiate(fs.readFileSync(process.argv[2]), go.importObject).then((result) => {
+    go.run(result.instance);
+}).catch((err) => {
+    console.error(err);
+    process.exit(1);
+});

testdata/wasmfunc.txt

@@ -0,0 +1,7 @@
+calling callback!
+inside callback! parameters:
+  parameter: 1
+  parameter: 2
+  parameter: 3
+  parameter: 4
+result from callback: 10