WASM: recover panics in compile goroutine to avoid unresolved browser promises

cmd/gh-aw-wasm/compile_recovery.go

@@ -0,0 +1,25 @@
+package main
+
+import (
+	"fmt"
+	"runtime/debug"
+)
+
+func compileWorkflowPanicError(r any) error {
+	return fmt.Errorf("compileWorkflow panic: %v\n%s", r, debug.Stack())
+}
+
+func runCompileWithRecovery(doCompile func() (any, error), resolve func(any), reject func(error)) {
+	defer func() {
+		if r := recover(); r != nil {
+			reject(compileWorkflowPanicError(r))
+		}
+	}()
+
+	result, err := doCompile()
+	if err != nil {
+		reject(err)
+		return
+	}
+	resolve(result)
+}

cmd/gh-aw-wasm/compile_recovery_test.go

@@ -0,0 +1,71 @@
+package main
+
+import (
+	"errors"
+	"strings"
+	"testing"
+)
+
+func TestRunCompileWithRecoverySuccess(t *testing.T) {
+	var resolved any
+	var rejected error
+
+	runCompileWithRecovery(
+		func() (any, error) { return "ok", nil },
+		func(result any) { resolved = result },
+		func(err error) { rejected = err },
+	)
+
+	if rejected != nil {
+		t.Fatalf("expected no rejection, got %v", rejected)
+	}
+	if resolved != "ok" {
+		t.Fatalf("expected resolve value %q, got %v", "ok", resolved)
+	}
+}
+
+func TestRunCompileWithRecoveryError(t *testing.T) {
+	want := errors.New("compile failed")
+	var resolved any
+	var rejected error
+
+	runCompileWithRecovery(
+		func() (any, error) { return nil, want },
+		func(result any) { resolved = result },
+		func(err error) { rejected = err },
+	)
+
+	if resolved != nil {
+		t.Fatalf("expected no resolve value, got %v", resolved)
+	}
+	if !errors.Is(rejected, want) {
+		t.Fatalf("expected rejection %v, got %v", want, rejected)
+	}
+}
+
+func TestRunCompileWithRecoveryPanic(t *testing.T) {
+	var resolved any
+	var rejected error
+
+	runCompileWithRecovery(
+		func() (any, error) {
+			panic("boom")
+		},
+		func(result any) { resolved = result },
+		func(err error) { rejected = err },
+	)
+
+	if resolved != nil {
+		t.Fatalf("expected no resolve value, got %v", resolved)
+	}
+	if rejected == nil {
+		t.Fatal("expected rejection from panic, got nil")
+	}
+	message := rejected.Error()
+	if !strings.Contains(message, "compileWorkflow panic: boom") {
+		t.Fatalf("expected panic prefix in rejection, got %q", message)
+	}
+	if !strings.Contains(message, "TestRunCompileWithRecoveryPanic") {
+		t.Fatalf("expected stack trace in rejection, got %q", message)
+	}
+}

cmd/gh-aw-wasm/main.go

@@ -47,13 +47,17 @@ func compileWorkflow(this js.Value, args []js.Value) any {
 
 		go func() {
 			defer handler.Release()
-
-			result, err := doCompile(markdown, files, filename)
-			if err != nil {
-				reject.Invoke(js.Global().Get("Error").New(err.Error()))
-				return
-			}
-			resolve.Invoke(result)
+			runCompileWithRecovery(
+				func() (any, error) {
+					return doCompile(markdown, files, filename)
+				},
+				func(result any) {
+					resolve.Invoke(result)
+				},
+				func(err error) {
+					reject.Invoke(js.Global().Get("Error").New(err.Error()))
+				},
+			)
 		}()
 
 		return nil