Add the NG01902 (Orphan field in signal forms) documentation page
to the Error Encyclopedia and change the ORPHAN_FIELD_PROPERTY
error code to -1902 so Angular's RuntimeError automatically appends
a link to angular.dev/errors/NG01902 in the thrown error message.
In signal forms, it is up to the user to guard hidden fields from being
rendered in the template. To help catch instances where it is
accidentally not guarded, this commit introduces a warning in dev mode.
Updates FormOptions to accept a submission configuration object.
This allows defining default submit options (action, validation behavior, etc.)
when creating the form, which can be overridden when calling submit().
Refactors the `ɵɵcontrolCreate` and `ɵɵcontrol` instructions to delegate control logic to the forms package via new `ɵngControlCreate` and `ɵngControlUpdate` lifecycle hooks. Previously, the logic for binding form state to native elements and custom controls was hardcoded within `@angular/core`.
**Compiler Changes:**
- Introduces a new compilation phase `specializeControlProperties` (in `control_directives.ts`).
- This phase detects properties named `formField` and specializes them into `ControlCreate` and `Control` IR opcodes.
- These opcodes emit `ɵɵcontrolCreate` and `ɵɵcontrol` instructions, respectively.
**Runtime Changes:**
- `ɵɵcontrolCreate` acts as the creation phase. It locates the control directive and invokes its `ɵngControlCreate` method.
- `ɵɵcontrol` acts as the update phase, and invokes the control directive's `ɵngControlUpdate` method (if present).
- Introduces a `passThroughInput` configuration in `ControlFeature`. This specifies the input name (e.g., `formField`) that triggers the control. If the runtime detects that this input is bound to multiple targets (e.g., the `FormField` directive *and* the host component), the control is flagged as "pass-through". In this state, `ɵngControlCreate` returns a no-op update function, deferring responsibility to the other consumer (e.g., the component managing the field itself).
**Forms Changes:**
- `FormField` directive implements `ɵngControlCreate` and `ɵngControlUpdate`.
- Inside this hook, `FormField` determines the type of control it is attached to (Native, CVA, or Custom Signal Control) and delegates to the appropriate handler (`nativeControlCreate`, `cvaControlCreate`, or `customControlCreate`).
- Consolidates all form binding logic within `@angular/forms/signals`, enabling support for new `FormValueControl` and `FormCheckboxControl` interfaces.
- Reorganizes the codebase by moving `FormField` from `api/` to `directive/` and splitting the binding logic into semantic pieces:
- `control_native.ts`, `control_cva.ts`, and `control_custom.ts` contain the specific handlers for each control type.
- `native.ts` and `select.ts` provide helpers for native element discovery and select-specific synchronization.
- `bindings.ts` manages the tracking and application of property/attribute bindings.
This PR adds the ability to manually register a binding with the
`FormField` directive. This is useful for a lower-level implementation
that takes the field tree as an `input()` rather than relying on the
automatic binding from `FormUiControl`.
