Function selectValueAccessor

packages/forms/src/directives/shared.ts:400–435

(
  dir: NgControl,
  valueAccessors: readonly ControlValueAccessor[] | null | undefined,
)

// TODO: vsavkin remove it once https://github.com/angular/angular/issues/3011 is implemented
export function selectValueAccessor(
  dir: NgControl,
  valueAccessors: readonly ControlValueAccessor[] | null | undefined,
): ControlValueAccessor | null {
  if (!valueAccessors) return null;

  if (!Array.isArray(valueAccessors) && (typeof ngDevMode === 'undefined' || ngDevMode))
    _throwInvalidValueAccessorError(dir);

  let defaultAccessor: ControlValueAccessor | undefined = undefined;
  let builtinAccessor: ControlValueAccessor | undefined = undefined;
  let customAccessor: ControlValueAccessor | undefined = undefined;

  valueAccessors.forEach((v: ControlValueAccessor) => {
    if (v.constructor === DefaultValueAccessor) {
      defaultAccessor = v;
    } else if (isBuiltInAccessor(v)) {
      if (builtinAccessor && (typeof ngDevMode === 'undefined' || ngDevMode))
        _throwError(dir, 'More than one built-in value accessor matches form control with');
      builtinAccessor = v;
    } else {
      if (customAccessor && (typeof ngDevMode === 'undefined' || ngDevMode))
        _throwError(dir, 'More than one custom value accessor matches form control with');
      customAccessor = v;
    }
  });

  if (customAccessor) return customAccessor;
  if (builtinAccessor) return builtinAccessor;
  if (defaultAccessor) return defaultAccessor;

  if (typeof ngDevMode === 'undefined' || ngDevMode) {
    _throwError(dir, 'No valid value accessor for form control with');
  }
  return null;
}

export function removeListItem<T>(list: T[], el: T): void {
  const index = list.indexOf(el);