By default, `toSignal` transforms an `Observable` into a `Signal`, including
the error channel of the Observable. When an error is received, the signal
begins throwing the error.
`toSignal` is intended to serve the same purpose as the `async` pipe, but
the async pipe has a different behavior with errors: it rejects them
outright, throwing them back into RxJS. Rx then propagates the error into
the browser's uncaught error handling logic. In the case of Angular, the
error is then caught by zone.js and reported via the application's
`ErrorHandler`.
This commit introduces a new option for `toSignal` called `rejectErrors`.
With that flag set, `toSignal` copies the async pipe's behavior, allowing
for easier migrations.
Fixes#51949
PR Close#52474
This commit cleans up the signatures of `toSignal` to better handle the
types of situations that it might be used in, and produce better type
inference results.
Fixes#50687Fixes#50591
Co-authored-by: Andrew Scott <atscott@google.com>
PR Close#51991
This commit reorganizes the Angular code a bit, and moves signals into a
newly defined `@angular/core/primitives` location. This will be used inside
g3 to allow non-Angular targets to depend on the signals core without
incurring a dependency on the whole framework.
PR Close#51986
Revert (with improvements of): dcf18dc74c
We recently landed a change that allows `toSignal` to be called
from within reactive contexts (e.g. `effect`/`computed`). After
more thorough investigatio and consideration with the team, we
feel like allowing `toSignal` to be called in such contexts is
encouraging non-ideal / hard-to-notice code patterns.
e.g. a new subscription to an observable is made every time `toSignal`
is invoked. There is no caching done here. Additionally, multiple new
subscriptions can trigger unintended side-effects- that may slow down
the app, result in incorrect/unexpected behavior or perform unnecessary
work.
Users should instead move the `toSignal` call outside of the `computed`
or `effect` and then read the signal values from within their `computed`. e.g.
```ts
computed(() => {
const smth = toSignal(coldObservable$)
return smth() + 2;
}
```
--> should instead be:
```ts
const smth = toSignal(coldObsverable$);
computed(() => smth() + 2);
```
In cases where a new subscription for each invocation is actually intended, a manual
subscription can be made. That way it's also much more obvious to users
that they are triggering side-effects every time, or causing new
subscriptions.
PR Close#52049
This PR moves the Observable subscription of toSignal outside of the
reactive context. As the result the toSignal calls are allowed in the
computed, effect and all other reactive consumers.
This is based on the reasoning that we already allow signals creation
in a reactive context. Plus a similar change was done to the async pipe
in the https://github.com/angular/angular/pull/50522Fixes#51027
PR Close#51831
This commit introduces an interface for `toSignal` options to mirror that of
`toObservable`, and adjusts docs for both symbols. It also adds the ability
for `toSignal` to manually specify `DestroyRef` (similarly to
`toObservable` accepting an injector) or for `toSignal` automatic cleanup to
be disabled (in which case the subscription persists until the Observable
completes). Either option allows `toSignal` to be used outside of a DI
context, like `toObservable`.
PR Close#50071
As described in
https://github.com/angular/angular/discussions/49681#discussioncomment-5628930,
if an `Observable` created from a signal with `toObservable` is
subscribed to in a template, it will initially have `null` as the value.
Immediately after the template is done executing, effects are flushed
and this results in the `AsyncPipe` getting a new value before the
`checkNoChanges` pass, resulting in `ExpressionChanged` error.
```
template: '{{obs$ | async}}'
...
obs$ = toObservable(signal(0));
```
Instead, this commit updates the `toObservable` to synchronously emit
the initial value to the Observable stream.
Side note here: We don't exactly encourage this pattern. Instead of
using `AsyncPipe`, the template should just read signals.
PR Close#49894
The initial value used for signals by default is now `undefined`. In
addition, there is a new option to express that the signal should emit a
value synchronously (`requireSync: true`). When this value is specified,
the function will throw _on creation_ if the subscribing to the
`Observable` does not result in a synchronous emit.
PR Close#49769
The change in effect timing collided with the introduction of these
rxjs-interop tests, resulting in them failing after the merge.
This commit adjusts the tests to rely on the real effect timing.
PR Close#49651
This commit implements an RxJS operator `takeUntilDestroyed` which
terminates an Observable when the current context (component, directive,
etc) is destroyed. `takeUntilDestroyed` will inject the current `DestroyRef`
if none is provided, or use one provided as an argument.
PR Close#49154
This commit adds the basic sketch for the implementation of `fromObservable`
and `fromSignal`, the two basic primitives which form the RxJS interop layer
with signals.
PR Close#49154
Alex Rickabaugh