Adds a basic failing test for settled
#458
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wagenet
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Nov 2, 2018
This avoids the issue detailed in emberjs#458.
wagenet
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Nov 2, 2018
This avoids the issue detailed in emberjs#458.
wagenet
added a commit
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Nov 2, 2018
This avoids the issue detailed in emberjs#458.
rwjblue
reviewed
Nov 2, 2018
|
:( |
As of Ember 3.2, `isSettled()` is no longer `true`, even immediately after `await settled()`. This is because `waitUntil` uses an RSVP Promise which resolves with a runloop. So when `waitUntil`'s promise is about to resolve, things _are_ settled, but as soon as we actually resolve, a new runloop is created which causes `isSettled()` to be `false`.
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Hmm... I can't reproduce the error locally, and it seem unrelated to the change. |
wagenet
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Nov 5, 2018
This avoids the issue detailed in emberjs#458.
|
Looks like the failure was related to old FF, using Latest ESR now. |
Turbo87
reviewed
Nov 6, 2018
krisselden
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Nov 6, 2018
Long ago in a galaxy far far away, Ember forced RSVP.Promise to
"resolve" on the Ember.run loop. At the time, this was meant to help
ease pain with folks receiving the dreaded "auto-run" assertion during
their tests, and to help ensure that promise resolution was coelesced
to avoid "thrashing" of the DOM. Unfortunately, the result of this
configuration is that code like the following behaves differently if
using native `Promise` vs `RSVP.Promise`:
```js
console.log('first');
Ember.run(() => Promise.resolve().then(() => console.log('second')));
console.log('third');
```
When `Promise` is the native promise that will log `'first', 'third',
'second'`, but when `Promise` is an `RSVP.Promise` that will log
`'first', 'second', 'third'`. The fact that `RSVP.Promise`s can be
**forced** to flush synchronously is very scary!
Now, lets talk about why we are configuring `RSVP`'s `async` below...
---
The following _should_ always be guaranteed:
```js
await settled();
isSettled() === true
```
Unfortunately, without the custom `RSVP` `async` configuration we cannot
ensure that `isSettled()` will be truthy. This is due to the fact that
Ember has configurate `RSVP` to resolve all promises in the run loop.
What that means practically is this:
1. all checks within `waitUntil` (used by `settled()` internally) are completed and we are "settled"
2. `waitUntil` resolves the promise that it returned (to signify that the world is "settled")
3. resolving the promise (since it is an `RSVP.Promise` and Ember has configured RSVP.Promise) creates
a new Ember.run loop in order to resolve
4. the presence of that new run loop means that we are no longer "settled"
5. `isSettled()` returns false 😭😭😭😭😭😭😭😭😭
This custom `RSVP.configure('async`, ...)` below provides a way to prevent the promises that are returned
from `settled` from causing this "loop" and instead "just use normal Promise semantics".
😩😫🙀
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hjdivad
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Nov 6, 2018
Turbo87
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Nov 6, 2018
wagenet
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This avoids the issue detailed in emberjs#458.
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As of Ember 3.2,
isSettled()is no longertrue, even immediatelyafter
await settled(). This is becausewaitUntiluses an RSVPPromise which resolves with a runloop. So when
waitUntil's promiseis about to resolve, things are settled, but as soon as we actually
resolve, a new runloop is created which causes
isSettled()to befalse.