fix(material/slide-toggle): move required validation into component

Currently required validation is implemented as a separate directive. This is problematic, because with standalone users would have to add two imports.

These changes move the required validation into the slide toggle and deprecate the old module.

src/material/slide-toggle/module.ts

@@ -7,24 +7,22 @@
  */
 
 import {NgModule} from '@angular/core';
-import {MatCommonModule, MatRippleModule} from '@angular/material/core';
+import {MatCommonModule} from '@angular/material/core';
 import {MatSlideToggle} from './slide-toggle';
 import {MatSlideToggleRequiredValidator} from './slide-toggle-required-validator';
 
-/** This module is used by both original and MDC-based slide-toggle implementations. */
+/**
+ * @deprecated No longer used, `MatSlideToggle` implements required validation directly.
+ * @breaking-change 19.0.0
+ */
 @NgModule({
   imports: [MatSlideToggleRequiredValidator],
   exports: [MatSlideToggleRequiredValidator],
 })
 export class _MatSlideToggleRequiredValidatorModule {}
 
 @NgModule({
-  imports: [
-    _MatSlideToggleRequiredValidatorModule,
-    MatCommonModule,
-    MatRippleModule,
-    MatSlideToggle,
-  ],
-  exports: [_MatSlideToggleRequiredValidatorModule, MatSlideToggle, MatCommonModule],
+  imports: [MatSlideToggle, MatCommonModule],
+  exports: [MatSlideToggle, MatCommonModule],
 })
 export class MatSlideToggleModule {}

src/material/slide-toggle/slide-toggle-required-validator.ts

@@ -9,6 +9,10 @@
 import {Directive, forwardRef, Provider} from '@angular/core';
 import {CheckboxRequiredValidator, NG_VALIDATORS} from '@angular/forms';
 
+/**
+ * @deprecated No longer used, `MatCheckbox` implements required validation directly.
+ * @breaking-change 19.0.0
+ */
 export const MAT_SLIDE_TOGGLE_REQUIRED_VALIDATOR: Provider = {
   provide: NG_VALIDATORS,
   useExisting: forwardRef(() => MatSlideToggleRequiredValidator),
@@ -22,6 +26,9 @@ export const MAT_SLIDE_TOGGLE_REQUIRED_VALIDATOR: Provider = {
  * where the value is always defined.
  *
  * Required slide-toggle form controls are valid when checked.
+ *
+ * @deprecated No longer used, `MatCheckbox` implements required validation directly.
+ * @breaking-change 19.0.0
  */
 @Directive({
   selector: `mat-slide-toggle[required][formControlName],

src/material/slide-toggle/slide-toggle.ts

@@ -19,13 +19,22 @@ import {
   Inject,
   Input,
   numberAttribute,
+  OnChanges,
   OnDestroy,
   Optional,
   Output,
+  SimpleChanges,
   ViewChild,
   ViewEncapsulation,
 } from '@angular/core';
-import {ControlValueAccessor, NG_VALUE_ACCESSOR} from '@angular/forms';
+import {
+  AbstractControl,
+  ControlValueAccessor,
+  NG_VALIDATORS,
+  NG_VALUE_ACCESSOR,
+  ValidationErrors,
+  Validator,
+} from '@angular/forms';
 import {ANIMATION_MODULE_TYPE} from '@angular/platform-browser/animations';
 import {FocusMonitor} from '@angular/cdk/a11y';
 import {
@@ -34,7 +43,10 @@ import {
 } from './slide-toggle-config';
 import {MatRipple} from '@angular/material/core';
 
-/** @docs-private */
+/**
+ * @deprecated Will stop being exported.
+ * @breaking-change 19.0.0
+ */
 export const MAT_SLIDE_TOGGLE_VALUE_ACCESSOR = {
   provide: NG_VALUE_ACCESSOR,
   useExisting: forwardRef(() => MatSlideToggle),
@@ -75,13 +87,23 @@ let nextUniqueId = 0;
   exportAs: 'matSlideToggle',
   encapsulation: ViewEncapsulation.None,
   changeDetection: ChangeDetectionStrategy.OnPush,
-  providers: [MAT_SLIDE_TOGGLE_VALUE_ACCESSOR],
+  providers: [
+    MAT_SLIDE_TOGGLE_VALUE_ACCESSOR,
+    {
+      provide: NG_VALIDATORS,
+      useExisting: MatSlideToggle,
+      multi: true,
+    },
+  ],
   standalone: true,
   imports: [MatRipple],
 })
-export class MatSlideToggle implements OnDestroy, AfterContentInit, ControlValueAccessor {
+export class MatSlideToggle
+  implements OnDestroy, AfterContentInit, OnChanges, ControlValueAccessor, Validator
+{
   private _onChange = (_: any) => {};
   private _onTouched = () => {};
+  private _validatorOnChange = () => {};
 
   private _uniqueId: string;
   private _checked: boolean = false;
@@ -211,6 +233,12 @@ export class MatSlideToggle implements OnDestroy, AfterContentInit, ControlValue
     });
   }
 
+  ngOnChanges(changes: SimpleChanges): void {
+    if (changes['required']) {
+      this._validatorOnChange();
+    }
+  }
+
   ngOnDestroy() {
     this._focusMonitor.stopMonitoring(this._elementRef);
   }
@@ -230,6 +258,16 @@ export class MatSlideToggle implements OnDestroy, AfterContentInit, ControlValue
     this._onTouched = fn;
   }
 
+  /** Implemented as a part of Validator. */
+  validate(control: AbstractControl<boolean>): ValidationErrors | null {
+    return this.required && control.value !== true ? {'required': true} : null;
+  }
+
+  /** Implemented as a part of Validator. */
+  registerOnValidatorChange(fn: () => void): void {
+    this._validatorOnChange = fn;
+  }
+
   /** Implemented as a part of ControlValueAccessor. */
   setDisabledState(isDisabled: boolean): void {
     this.disabled = isDisabled;

tools/public_api_guard/material/slide-toggle.md

@@ -4,6 +4,7 @@
 
 ```ts
 
+import { AbstractControl } from '@angular/forms';
 import { AfterContentInit } from '@angular/core';
 import { ChangeDetectorRef } from '@angular/core';
 import { CheckboxRequiredValidator } from '@angular/forms';
@@ -12,28 +13,32 @@ import { ElementRef } from '@angular/core';
 import { EventEmitter } from '@angular/core';
 import { FocusMonitor } from '@angular/cdk/a11y';
 import * as i0 from '@angular/core';
-import * as i2 from '@angular/material/core';
+import * as i3 from '@angular/material/core';
 import { InjectionToken } from '@angular/core';
+import { OnChanges } from '@angular/core';
 import { OnDestroy } from '@angular/core';
 import { Provider } from '@angular/core';
+import { SimpleChanges } from '@angular/core';
 import { ThemePalette } from '@angular/material/core';
 import { Type } from '@angular/core';
+import { ValidationErrors } from '@angular/forms';
+import { Validator } from '@angular/forms';
 
 // @public
 export const MAT_SLIDE_TOGGLE_DEFAULT_OPTIONS: InjectionToken<MatSlideToggleDefaultOptions>;
 
-// @public (undocumented)
+// @public @deprecated (undocumented)
 export const MAT_SLIDE_TOGGLE_REQUIRED_VALIDATOR: Provider;
 
-// @public
+// @public @deprecated (undocumented)
 export const MAT_SLIDE_TOGGLE_VALUE_ACCESSOR: {
     provide: InjectionToken<readonly ControlValueAccessor[]>;
     useExisting: Type<any>;
     multi: boolean;
 };
 
 // @public (undocumented)
-export class MatSlideToggle implements OnDestroy, AfterContentInit, ControlValueAccessor {
+export class MatSlideToggle implements OnDestroy, AfterContentInit, OnChanges, ControlValueAccessor, Validator {
     constructor(_elementRef: ElementRef, _focusMonitor: FocusMonitor, _changeDetectorRef: ChangeDetectorRef, tabIndex: string, defaults: MatSlideToggleDefaultOptions, animationMode?: string);
     ariaDescribedby: string;
     ariaLabel: string | null;
@@ -78,16 +83,20 @@ export class MatSlideToggle implements OnDestroy, AfterContentInit, ControlValue
     // (undocumented)
     ngAfterContentInit(): void;
     // (undocumented)
+    ngOnChanges(changes: SimpleChanges): void;
+    // (undocumented)
     ngOnDestroy(): void;
     _noopAnimations: boolean;
     registerOnChange(fn: any): void;
     registerOnTouched(fn: any): void;
+    registerOnValidatorChange(fn: () => void): void;
     required: boolean;
     setDisabledState(isDisabled: boolean): void;
     _switchElement: ElementRef<HTMLElement>;
     tabIndex: number;
     toggle(): void;
     readonly toggleChange: EventEmitter<void>;
+    validate(control: AbstractControl<boolean>): ValidationErrors | null;
     writeValue(value: any): void;
     // (undocumented)
     static ɵcmp: i0.ɵɵComponentDeclaration<MatSlideToggle, "mat-slide-toggle", ["matSlideToggle"], { "disabled": { "alias": "disabled"; "required": false; }; "disableRipple": { "alias": "disableRipple"; "required": false; }; "color": { "alias": "color"; "required": false; }; "tabIndex": { "alias": "tabIndex"; "required": false; }; "name": { "alias": "name"; "required": false; }; "id": { "alias": "id"; "required": false; }; "labelPosition": { "alias": "labelPosition"; "required": false; }; "ariaLabel": { "alias": "aria-label"; "required": false; }; "ariaLabelledby": { "alias": "aria-labelledby"; "required": false; }; "ariaDescribedby": { "alias": "aria-describedby"; "required": false; }; "required": { "alias": "required"; "required": false; }; "checked": { "alias": "checked"; "required": false; }; "hideIcon": { "alias": "hideIcon"; "required": false; }; }, { "change": "change"; "toggleChange": "toggleChange"; }, never, ["*"], true, never>;
@@ -118,18 +127,18 @@ export class MatSlideToggleModule {
     // (undocumented)
     static ɵinj: i0.ɵɵInjectorDeclaration<MatSlideToggleModule>;
     // (undocumented)
-    static ɵmod: i0.ɵɵNgModuleDeclaration<MatSlideToggleModule, never, [typeof _MatSlideToggleRequiredValidatorModule, typeof i2.MatCommonModule, typeof i2.MatRippleModule, typeof i3.MatSlideToggle], [typeof _MatSlideToggleRequiredValidatorModule, typeof i3.MatSlideToggle, typeof i2.MatCommonModule]>;
+    static ɵmod: i0.ɵɵNgModuleDeclaration<MatSlideToggleModule, never, [typeof i2.MatSlideToggle, typeof i3.MatCommonModule], [typeof i2.MatSlideToggle, typeof i3.MatCommonModule]>;
 }
 
-// @public
+// @public @deprecated
 export class MatSlideToggleRequiredValidator extends CheckboxRequiredValidator {
     // (undocumented)
     static ɵdir: i0.ɵɵDirectiveDeclaration<MatSlideToggleRequiredValidator, "mat-slide-toggle[required][formControlName],             mat-slide-toggle[required][formControl], mat-slide-toggle[required][ngModel]", never, {}, {}, never, never, true, never>;
     // (undocumented)
     static ɵfac: i0.ɵɵFactoryDeclaration<MatSlideToggleRequiredValidator, never>;
 }
 
-// @public
+// @public @deprecated (undocumented)
 export class _MatSlideToggleRequiredValidatorModule {
     // (undocumented)
     static ɵfac: i0.ɵɵFactoryDeclaration<_MatSlideToggleRequiredValidatorModule, never>;