host promise rejection

lib/flutter_qjs.dart

@@ -19,6 +19,9 @@ typedef JsMethodHandler = dynamic Function(String method, List args);
 /// Handler function to manage js module.
 typedef JsModuleHandler = String Function(String name);
 
+/// Handler to manage unhandled promise rejection.
+typedef JsHostPromiseRejectionHandler = void Function(String reason);
+
 class FlutterQjs {
   Pointer _rt;
   Pointer _ctx;
@@ -35,10 +38,17 @@ class FlutterQjs {
   /// Handler function to manage js module.
   JsModuleHandler moduleHandler;
 
+  /// Handler function to manage js module.
+  JsHostPromiseRejectionHandler hostPromiseRejectionHandler;
+
   /// Quickjs engine for flutter.
   ///
   /// Pass handlers to implement js-dart interaction and resolving modules.
-  FlutterQjs({this.methodHandler, this.moduleHandler, this.stackSize});
+  FlutterQjs(
+      {this.methodHandler,
+      this.moduleHandler,
+      this.stackSize,
+      this.hostPromiseRejectionHandler});
 
   _ensureEngine() {
     if (_rt != null) return;
@@ -51,14 +61,22 @@ class FlutterQjs {
           runtimeOpaques[rt]?.ref?.remove(obj);
           return Pointer.fromAddress(0);
         }
-        if (argv.address != 0 && method.address != 0) {
+        if (argv.address != 0) {
+          if (method.address == ctx.address) {
+            final errStr = parseJSException(ctx, perr: argv);
+            if (hostPromiseRejectionHandler != null) {
+              hostPromiseRejectionHandler(errStr);
+            } else {
+              print("unhandled promise rejection: $errStr");
+            }
+            return Pointer.fromAddress(0);
+          }
           if (methodHandler == null) throw Exception("No MethodHandler");
-          var argvs = jsToDart(ctx, argv);
           return dartToJs(
               ctx,
               methodHandler(
                 Utf8.fromUtf8(method.cast<Utf8>()),
-                argvs,
+                jsToDart(ctx, argv),
               ));
         }
         if (moduleHandler == null) throw Exception("No ModuleHandler");
@@ -69,11 +87,20 @@ class FlutterQjs {
         });
         return ret;
       } catch (e, stack) {
+        final errStr = e.toString() + "\n" + stack.toString();
+        if (method.address == 0) {
+          print("DartObject release error: " + errStr);
+          return Pointer.fromAddress(0);
+        }
+        if (method.address == ctx.address) {
+          print("host Promise Rejection Handler error: " + errStr);
+          return Pointer.fromAddress(0);
+        }
         var err = jsThrowInternalError(
           ctx,
-          e.toString() + "\n" + stack.toString(),
+          errStr,
         );
-        if (method.address == 0) {
+        if (argv.address == 0) {
           jsFreeValue(ctx, err);
           return Pointer.fromAddress(0);
         }

lib/isolate.dart

@@ -143,12 +143,17 @@ dynamic _decodeData(dynamic data, SendPort port,
 
 void _runJsIsolate(Map spawnMessage) async {
   SendPort sendPort = spawnMessage['port'];
-  JsMethodHandler methodHandler = spawnMessage['handler'];
   ReceivePort port = ReceivePort();
   sendPort.send(port.sendPort);
   var qjs = FlutterQjs(
     stackSize: spawnMessage['stackSize'],
-    methodHandler: methodHandler,
+    hostPromiseRejectionHandler: (reason) {
+      sendPort.send({
+        'type': 'hostPromiseRejection',
+        'reason': reason,
+      });
+    },
+    methodHandler: spawnMessage['handler'],
     moduleHandler: (name) {
       var ptr = allocate<Pointer<Utf8>>();
       ptr.value = Pointer.fromAddress(0);
@@ -222,11 +227,19 @@ class IsolateQjs {
   /// Asynchronously handler to manage js module.
   JsAsyncModuleHandler moduleHandler;
 
+  /// Handler function to manage js module.
+  JsHostPromiseRejectionHandler hostPromiseRejectionHandler;
+
   /// Quickjs engine runing on isolate thread.
   ///
   /// Pass handlers to implement js-dart interaction and resolving modules. The `methodHandler` is
   /// used in isolate, so **the handler function must be a top-level function or a static method**.
-  IsolateQjs({this.methodHandler, this.moduleHandler, this.stackSize});
+  IsolateQjs({
+    this.methodHandler,
+    this.moduleHandler,
+    this.stackSize,
+    this.hostPromiseRejectionHandler,
+  });
 
   _ensureEngine() {
     if (_sendPort != null) return;
@@ -247,6 +260,21 @@ class IsolateQjs {
         return;
       }
       switch (msg['type']) {
+        case 'hostPromiseRejection':
+          try {
+            final errStr = msg['reason'];
+            if (hostPromiseRejectionHandler != null) {
+              hostPromiseRejectionHandler(errStr);
+            } else {
+              print("unhandled promise rejection: $errStr");
+            }
+          } catch (e, stack) {
+            print("host Promise Rejection Handler error: " +
+                e.toString() +
+                "\n" +
+                stack.toString());
+          }
+          break;
         case 'module':
           var ptr = Pointer<Pointer>.fromAddress(msg['ptr']);
           try {

lib/wrapper.dart

@@ -78,10 +78,12 @@ class JSPromise extends JSRefValue {
       return true;
     }
     if (status["__rejected"] == true) {
+      final err = jsGetPropertyStr(ctx, val, "__error");
       completer.completeError(parseJSException(
         ctx,
-        e: jsGetPropertyStr(ctx, val, "__error"),
+        perr: err,
       ));
+      jsFreeValue(ctx, err);
       return true;
     }
     return false;
@@ -129,8 +131,9 @@ Pointer jsGetPropertyStr(Pointer ctx, Pointer val, String prop) {
   return jsProp;
 }
 
-String parseJSException(Pointer ctx, {Pointer e}) {
-  e = e ?? jsGetException(ctx);
+String parseJSException(Pointer ctx, {Pointer perr}) {
+  final e = perr ?? jsGetException(ctx);
+
   var err = jsToCString(ctx, e);
   if (jsValueGetTag(e) == JSTag.OBJECT) {
     Pointer stack = jsGetPropertyStr(ctx, e, "stack");
@@ -139,7 +142,7 @@ String parseJSException(Pointer ctx, {Pointer e}) {
     }
     jsFreeValue(ctx, stack);
   }
-  jsFreeValue(ctx, e);
+  if (perr == null) jsFreeValue(ctx, e);
   return err;
 }