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Promise of vertx cannot call then twice or more. about es4x HOT 4 OPEN

fantasy0v0 commented on June 2, 2024

Promise of vertx cannot call then twice or more.

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fantasy0v0 commented on June 2, 2024

then of io.reactiverse.es4x.Thenable Maybe should return new Future.

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fantasy0v0 commented on June 2, 2024

then of io.reactiverse.es4x.Thenable Maybe should return new Future.

I tried to modify it, but the problem was not simple.😣https://promisesaplus.com/#the-then-method

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fantasy0v0 commented on June 2, 2024

I try to implement this with native promises. I testing.

@Override
  public Value then(Value onResolve, Value onReject) {
    try {
      return JavaScript.createPromise(context, (_resolve, _reject) -> {
        Consumer<Object> onResolveNext = value -> {
          if (value instanceof Value _value) {
            if (JavaScript.isPromise(_value)) {
              _value.invokeMember("then", _resolve, _reject);
            } else {
              _resolve.execute(value);
            }
          } else {
            _resolve.execute(value);
          }
        };
        Consumer<Object> onRejectNext = err -> {
          if (err instanceof Value _value) {
            if (JavaScript.isPromise(_value)) {
              _value.invokeMember("then", _resolve, _reject);
            } else {
              _reject.execute(err);
            }
          } else {
            _reject.execute(err);
          }
        };
        future.onComplete(ar -> {
          if (ar.succeeded()) {
            T result = ar.result();
            if (onResolve != null && onResolve.canExecute()) {
              Value value = onResolve.execute(result);
              onResolveNext.accept(value);
            } else {
              _resolve.execute(result);
            }
          } else {
            Throwable cause = ar.cause();
            if (onReject != null && onReject.canExecute()) {
              Value value = onReject.execute(cause);
              onRejectNext.accept(value);
            } else {
              _reject.execute(cause);
            }
          }
        });
      });
    } catch (IOException e) {
      throw new RuntimeException(e);
    }
  }

JavaScript.createPromise implement:

public static Value createPromise(Context context, PromiseExecutor executor) throws IOException {
    Value bindings = context.getBindings("js");
    bindings.putMember("executor", executor);
    try {
      Source source = Source
        .newBuilder("js", "new Promise(executor)", null)
        .build();
      return context.eval(source);
    } finally {
      bindings.removeMember("executor");
    }
  }

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pmlopes commented on June 2, 2024

@fantasy0v0 yes, that is the vert.x behavior, JavaScript has a similar behavior:

let myPromise = new Promise(function(myResolve, myReject) {
  myResolve('OK'); // when successful
  myResolve('OK'); // when successful
});

// "Consuming Code" (Must wait for a fulfilled Promise)
myPromise.then(
  function(value) { console.log(value); },
  function(error) { console.log(error); }
);

With a small difference that calling multiple times will silently ignore the multiple calls. Let's update es4x to be like that, ignore the multiple calls.

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