The custom element implementation previously used a custom code path for
setting inputs, which contained bespoke code for writing input properties,
detecting whether inputs actually change, marking the component dirty,
scheduling and running CD, invoking `ngOnChanges`, etc. This custom logic
had several downsides:
* Its behavior different from how Angular components behave in a normal
template.
For example, inputs setters were invoked in `NgZone.run`, which (when
called from outside the zone) would trigger synchronous CD in the
component, _without_ calling `ngOnChanges`. Only when the custom rAF-
scheduled `detectChanges()` call triggered would `ngOnChanges` be called.
* CD always ran multiple times, because of the above. `NgZone.run` would
trigger CD, and then separately the scheduler would trigger CD.
* Signal inputs were not supported, since inputs were set via direct
property writes.
This change refactors the custom element implementation with two changes:
1. `ComponentRef.setInput` is used instead of a custom code path for
writing inputs.
This allows us to drop all the custom logic related to managing
`ngOnChanges`, since `setInput` does that under the hood. `ngOnChanges`
behavior now matches how the component would behave when _not_ rendered
as a custom element.
2. The custom rAF-based CD scheduler is removed in favor of the main Angular
scheduler, which now handles custom elements as necessary.
Running `NgZone.run` is sufficient to trigger CD when zones are used, and
the hybrid zoneless scheduler now ensures CD is scheduled when `setInput` is
called even with no ZoneJS enabled. As a result, the dedicated elements
scheduler is now only used when Angular's built-in scheduler is disabled.
As a concession to backwards compatibility, the element's view is also
marked for refresh when an input changes. Doing this allows CD to revisit
the element even if it becomes dirty during CD, mimicking how it would be
detected by the former elements scheduler unconditionally refreshing the
view a second time.
As a part of this change, the elements tests have been significantly
refactored. Previously all of Angular was faked/spied, which had a number
of downsides. For example, there were tests which asserted that change
detection only happens once when setting multiple inputs. This wasn't
actually the case (because of `NgZone.run` - see logic above) but the test
didn't catch the issue because it was only spying on `detectChanges()` which
isn't called from `ApplicationRef.tick()`. Even the components were fake.
Now, the tests use real Angular components and factories. They've also been
updated to not use `fakeAsync`.
A number of tests have been disabled, which were previously asserting
behavior that wasn't matching what was actually happening (as above). Other
tests were disabled due to real differences with `ngOnChanges` behavior,
where the current behavior could be seen as a bug.
Fixes#53981
BREAKING CHANGE: as part of switching away from custom CD behavior to the
hybrid scheduler, timing of change detection around custom elements has
changed subtly. These changes make elements more efficient, but can cause
tests which encoded assumptions about how or when elements would be checked
to require updating.
PR Close#56728
the createCustomEvent function's pupose is to create customEvents
even on browsers where `CustomEvent` is not a constructor,
`CustomEvent` is currently available in all supported browsers (since
IE11 support has ended), so remove the function as it is no longer
needed
PR Close#44703
Although in SSR we patch the global prototypes with DOM globals
like Element and Node, this patch does not occur before the
matches function is called in Angular Elements. This is similar
to the behavior in @angular/upgrade.
Fixes#24551
PR Close#37799
Detect server environment by checking `typeof window` and schedule render immediately instead of waiting for RAF.
This does not make Angular Elements work on platform-server. This is just the first step.
PR Close#23324
This PR was merged without API docs and general rollout plan.
We can't release this as is in 5.1 without a plan for documentation, cli integration, etc.
