angular/packages/forms/src/form_builder.ts

/**
 * @license
 * Copyright Google LLC All Rights Reserved.
 *
 * Use of this source code is governed by an MIT-style license that can be
 * found in the LICENSE file at https://angular.io/license
 */

import {inject, Injectable} from '@angular/core';

import {AsyncValidatorFn, ValidatorFn} from './directives/validators';
import {ReactiveFormsModule} from './form_providers';
import {AbstractControl, AbstractControlOptions, FormHooks} from './model/abstract_model';
import {FormArray, UntypedFormArray} from './model/form_array';
import {FormControl, FormControlOptions, FormControlState, UntypedFormControl} from './model/form_control';
import {FormGroup, FormRecord, UntypedFormGroup} from './model/form_group';

function isAbstractControlOptions(options: AbstractControlOptions|{[key: string]: any}|null|
                                  undefined): options is AbstractControlOptions {
  return !!options &&
      ((options as AbstractControlOptions).asyncValidators !== undefined ||
       (options as AbstractControlOptions).validators !== undefined ||
       (options as AbstractControlOptions).updateOn !== undefined);
}

/**
 * The union of all validator types that can be accepted by a ControlConfig.
 */
type ValidatorConfig = ValidatorFn|AsyncValidatorFn|ValidatorFn[]|AsyncValidatorFn[];

/**
 * The compiler may not always be able to prove that the elements of the control config are a tuple
 * (i.e. occur in a fixed order). This slightly looser type is used for inference, to catch cases
 * where the compiler cannot prove order and position.
 *
 * For example, consider the simple case `fb.group({foo: ['bar', Validators.required]})`. The
 * compiler will infer this as an array, not as a tuple.
 */
type PermissiveControlConfig<T> = Array<T|FormControlState<T>|ValidatorConfig>;

/**
 * ControlConfig<T> is a tuple containing a value of type T, plus optional validators and async
 * validators.
 *
 * @publicApi
 */
export type ControlConfig<T> = [T|FormControlState<T>, (ValidatorFn|(ValidatorFn[]))?, (AsyncValidatorFn|AsyncValidatorFn[])?];

// Disable clang-format to produce clearer formatting for this multiline type.
// clang-format off

/**
 * FormBuilder accepts values in various container shapes, as well as raw values.
 * Element returns the appropriate corresponding model class, given the container T.
 * The flag N, if not never, makes the resulting `FormControl` have N in its type.
 */
export type ɵElement<T, N extends null> =
  // The `extends` checks are wrapped in arrays in order to prevent TypeScript from applying type unions
  // through the distributive conditional type. This is the officially recommended solution:
  // https://www.typescriptlang.org/docs/handbook/2/conditional-types.html#distributive-conditional-types
  //
  // Identify FormControl container types.
  [T] extends [FormControl<infer U>] ? FormControl<U> :
  // Or FormControl containers that are optional in their parent group.
  [T] extends [FormControl<infer U>|undefined] ? FormControl<U> :
  // FormGroup containers.
  [T] extends [FormGroup<infer U>] ? FormGroup<U> :
  // Optional FormGroup containers.
  [T] extends [FormGroup<infer U>|undefined] ? FormGroup<U> :
  // FormRecord containers.
  [T] extends [FormRecord<infer U>] ? FormRecord<U> :
  // Optional FormRecord containers.
  [T] extends [FormRecord<infer U>|undefined] ? FormRecord<U> :
  // FormArray containers.
  [T] extends [FormArray<infer U>] ? FormArray<U> :
  // Optional FormArray containers.
  [T] extends [FormArray<infer U>|undefined] ? FormArray<U> :
  // Otherwise unknown AbstractControl containers.
  [T] extends [AbstractControl<infer U>] ? AbstractControl<U> :
  // Optional AbstractControl containers.
  [T] extends [AbstractControl<infer U>|undefined] ? AbstractControl<U> :
  // FormControlState object container, which produces a nullable control.
  [T] extends [FormControlState<infer U>] ? FormControl<U|N> :
  // A ControlConfig tuple, which produces a nullable control.
  [T] extends [PermissiveControlConfig<infer U>] ? FormControl<Exclude<U, ValidatorConfig>|N> :
  FormControl<T|N>;

// clang-format on

/**
 * @description
 * Creates an `AbstractControl` from a user-specified configuration.
 *
 * The `FormBuilder` provides syntactic sugar that shortens creating instances of a
 * `FormControl`, `FormGroup`, or `FormArray`. It reduces the amount of boilerplate needed to
 * build complex forms.
 *
 * @see [Reactive Forms Guide](guide/reactive-forms)
 *
 * @publicApi
 */
@Injectable({providedIn: ReactiveFormsModule})
export class FormBuilder {
  private useNonNullable: boolean = false;

  /**
   * @description
   * Returns a FormBuilder in which automatically constructed @see FormControl} elements
   * have `{nonNullable: true}` and are non-nullable.
   *
   * **Constructing non-nullable controls**
   *
   * When constructing a control, it will be non-nullable, and will reset to its initial value.
   *
   * ```ts
   * let nnfb = new FormBuilder().nonNullable;
   * let name = nnfb.control('Alex'); // FormControl<string>
   * name.reset();
   * console.log(name); // 'Alex'
   * ```
   *
   * **Constructing non-nullable groups or arrays**
   *
   * When constructing a group or array, all automatically created inner controls will be
   * non-nullable, and will reset to their initial values.
   *
   * ```ts
   * let nnfb = new FormBuilder().nonNullable;
   * let name = nnfb.group({who: 'Alex'}); // FormGroup<{who: FormControl<string>}>
   * name.reset();
   * console.log(name); // {who: 'Alex'}
   * ```
   * **Constructing *nullable* fields on groups or arrays**
   *
   * It is still possible to have a nullable field. In particular, any `FormControl` which is
   * *already* constructed will not be altered. For example:
   *
   * ```ts
   * let nnfb = new FormBuilder().nonNullable;
   * // FormGroup<{who: FormControl<string|null>}>
   * let name = nnfb.group({who: new FormControl('Alex')});
   * name.reset(); console.log(name); // {who: null}
   * ```
   *
   * Because the inner control is constructed explicitly by the caller, the builder has
   * no control over how it is created, and cannot exclude the `null`.
   */
  get nonNullable(): NonNullableFormBuilder {
    const nnfb = new FormBuilder();
    nnfb.useNonNullable = true;
    return nnfb as NonNullableFormBuilder;
  }

  /**
   * @description
   * Constructs a new `FormGroup` instance. Accepts a single generic argument, which is an object
   * containing all the keys and corresponding inner control types.
   *
   * @param controls A collection of child controls. The key for each child is the name
   * under which it is registered.
   *
   * @param options Configuration options object for the `FormGroup`. The object should have the
   * `AbstractControlOptions` type and might contain the following fields:
   * * `validators`: A synchronous validator function, or an array of validator functions.
   * * `asyncValidators`: A single async validator or array of async validator functions.
   * * `updateOn`: The event upon which the control should be updated (options: 'change' | 'blur'
   * | submit').
   */
  group<T extends {}>(
      controls: T,
      options?: AbstractControlOptions|null,
      ): FormGroup<{[K in keyof T]: ɵElement<T[K], null>}>;

  /**
   * @description
   * Constructs a new `FormGroup` instance.
   *
   * @deprecated This API is not typesafe and can result in issues with Closure Compiler renaming.
   * Use the `FormBuilder#group` overload with `AbstractControlOptions` instead.
   * Note that `AbstractControlOptions` expects `validators` and `asyncValidators` to be valid
   * validators. If you have custom validators, make sure their validation function parameter is
   * `AbstractControl` and not a sub-class, such as `FormGroup`. These functions will be called
   * with an object of type `AbstractControl` and that cannot be automatically downcast to a
   * subclass, so TypeScript sees this as an error. For example, change the `(group: FormGroup) =>
   * ValidationErrors|null` signature to be `(group: AbstractControl) => ValidationErrors|null`.
   *
   * @param controls A record of child controls. The key for each child is the name
   * under which the control is registered.
   *
   * @param options Configuration options object for the `FormGroup`. The legacy configuration
   * object consists of:
   * * `validator`: A synchronous validator function, or an array of validator functions.
   * * `asyncValidator`: A single async validator or array of async validator functions
   * Note: the legacy format is deprecated and might be removed in one of the next major versions
   * of Angular.
   */
  group(
      controls: {[key: string]: any},
      options: {[key: string]: any},
      ): FormGroup;

  group(controls: {[key: string]: any}, options: AbstractControlOptions|{[key: string]:
                                                                             any}|null = null):
      FormGroup {
    const reducedControls = this._reduceControls(controls);
    let newOptions: FormControlOptions = {};
    if (isAbstractControlOptions(options)) {
      // `options` are `AbstractControlOptions`
      newOptions = options;
    } else if (options !== null) {
      // `options` are legacy form group options
      newOptions.validators = (options as any).validator;
      newOptions.asyncValidators = (options as any).asyncValidator;
    }
    return new FormGroup(reducedControls, newOptions);
  }

  /**
   * @description
   * Constructs a new `FormRecord` instance. Accepts a single generic argument, which is an object
   * containing all the keys and corresponding inner control types.
   *
   * @param controls A collection of child controls. The key for each child is the name
   * under which it is registered.
   *
   * @param options Configuration options object for the `FormRecord`. The object should have the
   * `AbstractControlOptions` type and might contain the following fields:
   * * `validators`: A synchronous validator function, or an array of validator functions.
   * * `asyncValidators`: A single async validator or array of async validator functions.
   * * `updateOn`: The event upon which the control should be updated (options: 'change' | 'blur'
   * | submit').
   */
  record<T>(controls: {[key: string]: T}, options: AbstractControlOptions|null = null):
      FormRecord<ɵElement<T, null>> {
    const reducedControls = this._reduceControls(controls);
    // Cast to `any` because the inferred types are not as specific as Element.
    return new FormRecord(reducedControls, options) as any;
  }

  /** @deprecated Use `nonNullable` instead. */
  control<T>(formState: T|FormControlState<T>, opts: FormControlOptions&{
    initialValueIsDefault: true
  }): FormControl<T>;

  control<T>(formState: T|FormControlState<T>, opts: FormControlOptions&{nonNullable: true}):
      FormControl<T>;

  /**
   * @deprecated When passing an `options` argument, the `asyncValidator` argument has no effect.
   */
  control<T>(
      formState: T|FormControlState<T>, opts: FormControlOptions,
      asyncValidator: AsyncValidatorFn|AsyncValidatorFn[]): FormControl<T|null>;

  control<T>(
      formState: T|FormControlState<T>,
      validatorOrOpts?: ValidatorFn|ValidatorFn[]|FormControlOptions|null,
      asyncValidator?: AsyncValidatorFn|AsyncValidatorFn[]|null): FormControl<T|null>;

  /**
   * @description
   * Constructs a new `FormControl` with the given state, validators and options. Sets
   * `{nonNullable: true}` in the options to get a non-nullable control. Otherwise, the
   * control will be nullable. Accepts a single generic argument, which is the type  of the
   * control's value.
   *
   * @param formState Initializes the control with an initial state value, or
   * with an object that contains both a value and a disabled status.
   *
   * @param validatorOrOpts A synchronous validator function, or an array of
   * such functions, or a `FormControlOptions` object that contains
   * validation functions and a validation trigger.
   *
   * @param asyncValidator A single async validator or array of async validator
   * functions.
   *
   * @usageNotes
   *
   * ### Initialize a control as disabled
   *
   * The following example returns a control with an initial value in a disabled state.
   *
   * <code-example path="forms/ts/formBuilder/form_builder_example.ts" region="disabled-control">
   * </code-example>
   */
  control<T>(
      formState: T|FormControlState<T>,
      validatorOrOpts?: ValidatorFn|ValidatorFn[]|FormControlOptions|null,
      asyncValidator?: AsyncValidatorFn|AsyncValidatorFn[]|null): FormControl {
    let newOptions: FormControlOptions = {};
    if (!this.useNonNullable) {
      return new FormControl(formState, validatorOrOpts, asyncValidator);
    }
    if (isAbstractControlOptions(validatorOrOpts)) {
      // If the second argument is options, then they are copied.
      newOptions = validatorOrOpts;
    } else {
      // If the other arguments are validators, they are copied into an options object.
      newOptions.validators = validatorOrOpts;
      newOptions.asyncValidators = asyncValidator;
    }
    return new FormControl<T>(formState, {...newOptions, nonNullable: true});
  }

  /**
   * Constructs a new `FormArray` from the given array of configurations,
   * validators and options. Accepts a single generic argument, which is the type of each control
   * inside the array.
   *
   * @param controls An array of child controls or control configs. Each child control is given an
   *     index when it is registered.
   *
   * @param validatorOrOpts A synchronous validator function, or an array of such functions, or an
   *     `AbstractControlOptions` object that contains
   * validation functions and a validation trigger.
   *
   * @param asyncValidator A single async validator or array of async validator functions.
   */
  array<T>(
      controls: Array<T>, validatorOrOpts?: ValidatorFn|ValidatorFn[]|AbstractControlOptions|null,
      asyncValidator?: AsyncValidatorFn|AsyncValidatorFn[]|null): FormArray<ɵElement<T, null>> {
    const createdControls = controls.map(c => this._createControl(c));
    // Cast to `any` because the inferred types are not as specific as Element.
    return new FormArray(createdControls, validatorOrOpts, asyncValidator) as any;
  }

  /** @internal */
  _reduceControls<T>(controls:
                         {[k: string]: T|ControlConfig<T>|FormControlState<T>|AbstractControl<T>}):
      {[key: string]: AbstractControl} {
    const createdControls: {[key: string]: AbstractControl} = {};
    Object.keys(controls).forEach(controlName => {
      createdControls[controlName] = this._createControl(controls[controlName]);
    });
    return createdControls;
  }

  /** @internal */
  _createControl<T>(controls: T|FormControlState<T>|ControlConfig<T>|FormControl<T>|
                    AbstractControl<T>): FormControl<T>|FormControl<T|null>|AbstractControl<T> {
    if (controls instanceof FormControl) {
      return controls as FormControl<T>;
    } else if (controls instanceof AbstractControl) {  // A control; just return it
      return controls;
    } else if (Array.isArray(controls)) {  // ControlConfig Tuple
      const value: T|FormControlState<T> = controls[0];
      const validator: ValidatorFn|ValidatorFn[]|null = controls.length > 1 ? controls[1]! : null;
      const asyncValidator: AsyncValidatorFn|AsyncValidatorFn[]|null =
          controls.length > 2 ? controls[2]! : null;
      return this.control<T>(value, validator, asyncValidator);
    } else {  // T or FormControlState<T>
      return this.control<T>(controls);
    }
  }
}

/**
 * @description
 * `NonNullableFormBuilder` is similar to {@link FormBuilder}, but automatically constructed
 * {@link FormControl} elements have `{nonNullable: true}` and are non-nullable.
 *
 * @publicApi
 */
@Injectable({
  providedIn: ReactiveFormsModule,
  useFactory: () => inject(FormBuilder).nonNullable,
})
export abstract class NonNullableFormBuilder {
  /**
   * Similar to `FormBuilder#group`, except any implicitly constructed `FormControl`
   * will be non-nullable (i.e. it will have `nonNullable` set to true). Note
   * that already-constructed controls will not be altered.
   */
  abstract group<T extends {}>(
      controls: T,
      options?: AbstractControlOptions|null,
      ): FormGroup<{[K in keyof T]: ɵElement<T[K], never>}>;

  /**
   * Similar to `FormBuilder#record`, except any implicitly constructed `FormControl`
   * will be non-nullable (i.e. it will have `nonNullable` set to true). Note
   * that already-constructed controls will not be altered.
   */
  abstract record<T>(
      controls: {[key: string]: T},
      options?: AbstractControlOptions|null,
      ): FormRecord<ɵElement<T, never>>;

  /**
   * Similar to `FormBuilder#array`, except any implicitly constructed `FormControl`
   * will be non-nullable (i.e. it will have `nonNullable` set to true). Note
   * that already-constructed controls will not be altered.
   */
  abstract array<T>(
      controls: Array<T>, validatorOrOpts?: ValidatorFn|ValidatorFn[]|AbstractControlOptions|null,
      asyncValidator?: AsyncValidatorFn|AsyncValidatorFn[]|null): FormArray<ɵElement<T, never>>;

  /**
   * Similar to `FormBuilder#control`, except this overridden version of `control` forces
   * `nonNullable` to be `true`, resulting in the control always being non-nullable.
   */
  abstract control<T>(
      formState: T|FormControlState<T>,
      validatorOrOpts?: ValidatorFn|ValidatorFn[]|AbstractControlOptions|null,
      asyncValidator?: AsyncValidatorFn|AsyncValidatorFn[]|null): FormControl<T>;
}

/**
 * UntypedFormBuilder is the same as @see FormBuilder, but it provides untyped controls.
 */
@Injectable({providedIn: ReactiveFormsModule})
export class UntypedFormBuilder extends FormBuilder {
  /**
   * Like `FormBuilder#group`, except the resulting group is untyped.
   */
  override group(
      controlsConfig: {[key: string]: any},
      options?: AbstractControlOptions|null,
      ): UntypedFormGroup;

  /**
   * @deprecated This API is not typesafe and can result in issues with Closure Compiler renaming.
   * Use the `FormBuilder#group` overload with `AbstractControlOptions` instead.
   */
  override group(
      controlsConfig: {[key: string]: any},
      options: {[key: string]: any},
      ): UntypedFormGroup;

  override group(
      controlsConfig: {[key: string]: any},
      options: AbstractControlOptions|{[key: string]: any}|null = null): UntypedFormGroup {
    return super.group(controlsConfig, options);
  }

  /**
   * Like `FormBuilder#control`, except the resulting control is untyped.
   */
  override control(
      formState: any, validatorOrOpts?: ValidatorFn|ValidatorFn[]|FormControlOptions|null,
      asyncValidator?: AsyncValidatorFn|AsyncValidatorFn[]|null): UntypedFormControl {
    return super.control(formState, validatorOrOpts, asyncValidator);
  }

  /**
   * Like `FormBuilder#array`, except the resulting array is untyped.
   */
  override array(
      controlsConfig: any[],
      validatorOrOpts?: ValidatorFn|ValidatorFn[]|AbstractControlOptions|null,
      asyncValidator?: AsyncValidatorFn|AsyncValidatorFn[]|null): UntypedFormArray {
    return super.array(controlsConfig, validatorOrOpts, asyncValidator);
  }
}