Function cvaControlCreate

packages/forms/signals/src/directive/control_cva.ts:34–117

(
  host: ControlDirectiveHost,
  parent: FormField<unknown>,
)

}

export function cvaControlCreate(
  host: ControlDirectiveHost,
  parent: FormField<unknown>,
): () => void {
  const bindings = createBindings<ControlBindingKey | 'controlValue'>();

  parent.controlValueAccessor!.registerOnChange((value: unknown) => {
    // Update tracking for 'controlValue' here so that when the effect runs,
    // `bindingUpdated` sees that the model value matches the last seen view value.
    // This prevents the framework from writing the same value back to the CVA (CVA loopback).
    bindings['controlValue'] = value;
    parent.state().controlValue.set(value);
  });
  parent.controlValueAccessor!.registerOnTouched(() => parent.state().markAsTouched());

  const legacyValidators = parent.injector.get(NG_VALIDATORS, null, {optional: true, self: true});
  if (legacyValidators) {
    let version: WritableSignal<number> | undefined;

    for (const v of legacyValidators) {
      if (isValidatorObject(v) && v.registerOnValidatorChange) {
        version ??= signal(0);
        v.registerOnValidatorChange(() => {
          version!.update((n) => n + 1);
        });
      }
    }

    const validatorFns = legacyValidators.map((v) =>
      typeof v === 'function' ? (v as ValidatorFn) : v.validate.bind(v),
    );
    const mergedValidator = Validators.compose(validatorFns);

    const parseErrors = computed(() => {
      // Read the `version` signal to re-run the validator when legacy validators trigger their change callbacks.
      version?.();
      const errors = mergedValidator ? mergedValidator(parent.interopNgControl.control) : null;
      return reactiveErrorsToSignalErrors(errors, parent.interopNgControl.control);
    });
    // We must cast here because `CompatValidationError` claims to have `fieldTree` statically (to
    // satisfy `ValidationState` elsewhere), but at construction it is created without it and acts as
    // `WithoutFieldTree` initially.
    parent.parseErrorsSource.set(
      parseErrors as unknown as Signal<readonly ValidationError.WithoutFieldTree[]>,
    );
  }

  parent.registerAsBinding({
    reset: () => {
      const value = parent.state().value();
      bindings['controlValue'] = value;
      untracked(() => parent.controlValueAccessor!.writeValue(value));
    },
  });

  return () => {
    const fieldState = parent.state();
    const value = fieldState.value();