JS Interop works with DDC but not with Dart2JS - dart

Question

Dart 2.7
build_runner: 1.7.3
build_web_compilers: 2.9.0
I've created an interface for GoJS using the package js: https://github.com/jodinathan/gojs_dart/
The problem is that it works flawlessly in DDC but throws an exception when using with Dart2JS.
Here is a small repro you can check:
https://github.com/jodinathan/gojs_dart/tree/master/example/flowchart
The error seems to be in the line ..bind(GoJSBinding('text').makeTwoWay())
I think it can't find the bind() function, however, it can when in DDC.
Any ideas on how I could solve this?
The issue is in the dart-sdk: https://github.com/dart-lang/sdk/issues/40434

Answer 1

It looks like dart2js requires an external factory constructor on all classes while dartdevc does not. So for instance for the first error it hits today you have a class like this:
#JS('Node')
class GoJSNode extends GoJSPart {}
And it should look like this:
#JS('Node')
class GoJSNode extends GoJSPart {
external factory GoJSNode();
}