Uncaught exception when trying to chrome.runtime.sendMessage()

[matofesi]

I'm not sure if it's me or is it a problem withe the library... What I'm trying to do is send a message between extensions blocks. I set a listener in one file with chrome.runtime.onMessage.listen() and then send messages with

chrome.runtime.sendMessage(
null,
{ "cmd": "saved" },
SendMessageOptions(includeTlsChannelId: false)
);

It seems to be working - messages are being delivered, but every time I do sendMessage I get exception like that in console:

Uncaught (in promise) Error: TypeError: null: type 'minified:aH' is not a subtype of type 'Object'
    at Object.b (offscreen.dart.js:271:18)
    at H.hr [as a] (offscreen.dart.js:783:9)
    at H.hD (offscreen.dart.js:742:10)
    at b_.a5 (offscreen.dart.js:2491:16)
    at dJ.$1 (offscreen.dart.js:3171:21)

Should I try to do something else or is there something wrong with the library?

[xvrh]

Hi, can you compile the application with --profile mode to get an unminified stack trace.
That would help. Thanks.

[matofesi]

I know that's probably a stupid question, but... how do I do that? I'm building an extension and I compile it with webdev build. I found some options for build_web_compilers but I don't see how to add --profile.

Oh... Unless what you asked about was this:

Uncaught (in promise) Error: TypeError: null: type 'JSNull' is not a subtype of type 'Object'
    at Object.wrapException (js_helper.dart:1190:19)
    at Rti._asObject [as _as] (rti.dart:1466:3)
    at _AsyncCompleter.complete$1 (future_impl.dart:44:41)
    at promiseToFuture_closure.call$1 (js_util_patch.dart:483:49)

[mishkov]

I am sure in all JS stuff and I cannot debug the code but after many tries and experiments I think I have found the solution of this exception. The reason is that the the method sendMessage have non-nullable return type Object and inside of it also there is a ! as well as the generic type for promiseToFuture call is not nullable. See:

Future<Object> sendMessage(
  String? extensionId,
  Object message,
  SendMessageOptions? options,
) async {
  var $res = await promiseToFuture<JSAny>($js.chrome.runtime.sendMessage(
    extensionId,
    message.jsify()!,
    options?.toJS,
  ));
  return $res.dartify()!;
}

So when as I understand

$js.chrome.runtime.sendMessage(
  extensionId,
  message.jsify()!,
  options?.toJS,
)

returns null it causes the exception because the JSAny cannot be null

/// A non-nullish JavaScript value.
///
/// A [JSAny] can be any JavaScript value except JavaScript `null` and
/// `undefined`. JavaScript `null` and `undefined` are instead converted to Dart
/// `null` by the compiler. Therefore, <code>[JSAny]?</code> is the top type of
/// the type hierarchy as it includes nullish JavaScript values as well.
extension type JSAny._(JSAnyRepType _jsAny) implements Object {}

and the line return $res.dartify()!; will contain call on null object.

@matofesi The temporary solution is to locally modify the source code of the library as follow

- Future<Object> sendMessage(
+ Future<Object?> sendMessage(
  String? extensionId,
  Object message,
  SendMessageOptions? options,
) async {
-   var $res = await promiseToFuture<JSAny>($js.chrome.runtime.sendMessage(
+   var $res = await promiseToFuture<JSAny?>($js.chrome.runtime.sendMessage(
    extensionId,
    message.jsify()!,
    options?.toJS,
  ));
-   return $res.dartify()!;
+  return $res?.dartify();
}

I am gonna prepare PR for this Issue as soon as possible