Updates signal forms to pass the full `Field` directive to the class
configuration functions, rather than just the state. This allows
developers to take the element as well as the state into consideration
when deciding classes to apply.
Closes#65762
BREAKING CHANGE: The shape of `SignalFormsConfig.classes` has changed
Previously each function in the `classes` map took a `FieldState`. Now
it takes a `Field` directive.
For example if you previously had:
```
provideSignalFormsConfig({
classes: {
'my-valid': (state) => state.valid()
}
})
```
You would need to update to:
```
provideSignalFormsConfig({
classes: {
'my-valid': ({state}) => state().valid()
}
})
```
This PR makes a number of changes to the metadata API to address design
flaws in the previous API. Some of the changes include:
- Replaces the previous `MetadataKey` and `AggregateMetadataKey` with a
single unified `MetadataKey` that is used for all metadata.
- The new `MetadataKey` is only defined for fields that explicitly set
it in their schema logic
- All metadata now has reducer / aggregate behavior
- The new `MetadataKey` has an option to create a managed key which
wraps the result of its computed aggregate into some other structure
such as a `Resource` or `linkedSignal`
- There are now two APIs to create metadata keys
- `createMetadataKey` for pure computed metadata
- `createManagedMetadataKey` for metadata that manages its computation
internally
Previously, navigating a `FieldTree` in signal forms involved reactive reads
of the value of the parent field(s), both directly and via `.childrenMap()`.
This meant that on _any_ change to the value of a field, reactive
notifications would trigger updates of computeds, reruns of effects, etc.
So for example, this effect would run on every change to the form:
```ts
const f = form(signal({data: 'abc', unrelated: 0}));
effect(() => {
// accessing f.data incurs a dependency on f().value() which changes
// on every change in the whole form
console.log(f.data().value());
});
```
This is deeply counterintuitive and troublesome when attempting to write
effect logic, and also results in `computed`s unnecessarily updating.
This change introduces the concept of a "reader" computed, which memoizes
the access of a field at a given key via the reactive graph. With this, the
same `f.data` access above now depends on the `data` reader in `f` only,
which is effectively a constant computed. As a result, the effect only
reruns on changes to `data`'s value, as intended.
PR Close#65802
Adds a DI configuration option for signal forms that allows the
developer to specify CSS classes that should be automatically added
by the `Field` directive based on the field's status.
Currently we maintain the pathKeys internally, but do not expose them
through the `FieldContext`, this PR updates the `FieldContext` to expose
this property.
SkyZeroZx