In the original `Promise` impelmentation, zone.js follow the spec from
https://promisesaplus.com/#point-51.
```
const p1 = Promise.resolve(1);
const p2 = Promise.resolve(p1);
p1 === p2; // false
```
in this case, `p2` should be the same status with `p1` but they are
still different instances.
And for some edge case.
```
class MyPromise extends Promise {
constructor(sub) {
super((res) => res(null));
this.sub = sub;
}
then(onFufilled, onRejected) {
this.sub.then(onFufilled, onRejected);
}
}
const p1 = new Promise(setTimeout(res), 100);
const myP = new MyPromise(p1);
const r = await myP;
r === 1; // false
```
So in the above code, `myP` is not the same instance with `p1`,
and since `myP` is resolved in constructor, so `await myP` will
just pass without waiting for `p1`.
And in the current `tc39` spec here https://tc39.es/ecma262/multipage/control-abstraction-objects.html#sec-promise-resolve
`Promise.resolve(subP)` should return `subP`.
```
const p1 = Promise.resolve(1);
const p2 = Promise.resolve(p1);
p1 === p2; // true
```
So the above `MyPromise` can wait for the `p1` correctly.
PR Close#53423
Before this commit, zone.js wraps the uncaught promise rejection error
to a new Error object includes more information such as Zone stack
traces. This feature is provided from the very beginning of Zone.js,
but this feature becomes very annoying and make the user difficult to
debug.
So this commit disable this wrapping behavior by default, and user can
enable this feature back by setting
`DISABLE_WRAPPING_UNCAUGHT_PROMISE_REJECTION` to `false`.
PR Close#52492
The native promise implementation logs unhandled promise rejections after `onFinally`
has been called. We may rely on the `scheduledByFinally` argument, which is `false` by
default, to avoid creating a breaking change; this will also allow us to reduce the number of
changes. The `finally` function should not silence unhandled promise rejections, because
they're not silenced in any implementation. If the `scheduleResolveOrReject` is called within
the `finally` we won't clear unhandled rejections. We'll keep the same behaviour if the
`scheduleResolveOrReject` is called within the `then`.
PR Close#43206
PR Close#45449
Close#44913
The following case is not handled correctly by `zone.js`.
```
const delayedPromise = new Promise((resolve) => {
setTimeout(resolve, 1, 'timeout');
});
new Promise((resolve) => {
resolve(delayedPromise);
resolve('second call');
}).then(console.log);
```
It should output `timeout`, since the promise is resolved by the
1st resolve, the `second call` should be ignored.
So this is a bug that the original implementation not ensure the
`resolve` is only called once.
PR Close#45283
We must read `Symbol.species` safely because `this` may be anything. For instance, `this`
may be an object without a prototype (created through `Object.create(null)`); thus
`this.constructor` will be undefined. One of the use cases is SystemJS creating
prototype-less objects (modules) via `Object.create(null)`. The SystemJS creates an empty
object and copies promise properties into that object (within the `getOrCreateLoad`
function). The zone.js then checks if the resolved value has the `then` method and invokes
it with the `value` context. Otherwise, this will throw an error: `TypeError: Cannot read
properties of undefined (reading 'Symbol(Symbol.species)')`.
PR Close#45369
Close#38334.
zone.js provides a flag DISABLE_WRAPPING_UNCAUGHT_PROMISE_REJECTION to let zone.js
throw the original error instead of wrap it when uncaught promise rejection found.
But the rejection value could be anything includes primitive value such as number.
In that case, we should not attach any additional properties to the value.
PR Close#38476
In the early Zone.js versions (< 0.10.3), `ZoneAwarePromise` did not support `Symbol.species`,
so when user used a 3rd party `Promise` such as `es6-promise`, and try to load the promise library after import of `zone.js`, the loading promise library will overwrite the patched `Promise` from `zone.js` and will break `Promise` semantics with respect to `zone.js`.
Starting with `zone.js` 0.10.3, `Symbol.species` is supported therefore this will not longer be an issue. (https://github.com//pull/34533)
Before 0.10.3, the logic in zone.js tried to handle the case in the wrong way. It did so by overriding the descriptor of `global.Promise`, to allow the 3rd party libraries to override native `Promise` instead of `ZoneAwarePromise`. This is not the correct solution, and since the `Promise.species` is now supported, the 3rd party solution of overriding `global.Promise` is no longer needed.
PR removes the wrong work around logic. (This will improve the bundle size.)
PR Close#36851
Close#36142
In Firefox extensions, the `window.fetch` is not configurable, that means
```
const desc = Object.getOwnPropertyDescriptor(window, 'fetch');
desc.writable === false;
```
So in this case, we should not try to patch `fetch`, otherwise, it will
throw error ('fetch is ReadOnly`)
PR Close#36311
Close#27840.
By default, `zone.js` wrap uncaught promise error and wrap it to a new Error object with some
additional information includes the value of the error and the stack trace.
Consider the following example:
```
Zone.current
.fork({
name: 'promise-error',
onHandleError: (delegate: ZoneDelegate, current: Zone, target: Zone, error: any): boolean => {
console.log('caught an error', error);
delegate.handleError(target, error);
return false;
}
}).run(() => {
const originalError = new Error('testError');
Promise.reject(originalError);
});
```
The `promise-error` zone catches a wrapped `Error` object whose `rejection` property equals
to the original error, and the message will be `Uncaught (in promise): testError....`,
You can disable this wrapping behavior by defining a global configuraiton
`__zone_symbol__DISABLE_WRAPPING_UNCAUGHT_PROMISE_REJECTION = true;` before importing `zone.js`.
PR Close#35873
JiaLiPassion