fix(checkbox): update MatCheckbox disabled setter to trigger change detection

This is related to #11056, which is a similar fix for
MatRadioButton.

The MatCheckbox component instance may be accessed directly by a parent component using
ViewChild/ContentChild. Since MatCheckbox uses OnPush change detection setting the disabled property
directly currently doesn't cause change detection leading to a stale or broken state. Accessing it
through a template binding does correctly trigger change detection on MatCheckbox (there are already
test cases for this method). We need to add a manual call to markForCheck, or else MatCheckbox will
never get kicked if disabled is set directly on the component instance.

Related open Angular bug: angular/angular#20611

Author: stevenyxu

src/lib/checkbox/checkbox.spec.ts

@@ -1,6 +1,6 @@
 import {ComponentFixture, fakeAsync, TestBed, tick, flush} from '@angular/core/testing';
 import {FormControl, FormsModule, NgModel, ReactiveFormsModule} from '@angular/forms';
-import {Component, DebugElement} from '@angular/core';
+import {Component, DebugElement, ViewChild} from '@angular/core';
 import {By} from '@angular/platform-browser';
 import {dispatchFakeEvent} from '@angular/cdk/testing';
 import {MatCheckbox, MatCheckboxChange, MatCheckboxModule} from './index';
@@ -28,6 +28,7 @@ describe('MatCheckbox', () => {
         CheckboxWithFormControl,
         CheckboxWithoutLabel,
         CheckboxWithTabindexAttr,
+        CheckboxUsingViewChild,
       ]
     });
 
@@ -786,7 +787,6 @@ describe('MatCheckbox', () => {
   });
 
   describe('with native tabindex attribute', () => {
-
     it('should properly detect native tabindex attribute', fakeAsync(() => {
       fixture = TestBed.createComponent(CheckboxWithTabindexAttr);
       fixture.detectChanges();
@@ -799,6 +799,61 @@ describe('MatCheckbox', () => {
     }));
   });
 
+  describe('using ViewChild', () => {
+    let checkboxDebugElement: DebugElement;
+    let checkboxNativeElement: HTMLElement;
+    let testComponent: CheckboxUsingViewChild;
+
+    beforeEach(() => {
+      fixture = TestBed.createComponent(CheckboxUsingViewChild);
+      fixture.detectChanges();
+
+      checkboxDebugElement = fixture.debugElement.query(By.directive(MatCheckbox));
+      checkboxNativeElement = checkboxDebugElement.nativeElement;
+      testComponent = fixture.debugElement.componentInstance;
+    });
+
+    it('should toggle checkbox disabledness correctly', () => {
+      const checkboxInstance = checkboxDebugElement.componentInstance;
+      const inputElement = <HTMLInputElement>checkboxNativeElement.querySelector('input');
+      expect(checkboxInstance.disabled).toBe(false);
+      expect(checkboxNativeElement.classList).not.toContain('mat-checkbox-disabled');
+      expect(inputElement.tabIndex).toBe(0);
+      expect(inputElement.disabled).toBe(false);
+
+      testComponent.isDisabled = true;
+      fixture.detectChanges();
+
+      expect(checkboxInstance.disabled).toBe(true);
+      expect(checkboxNativeElement.classList).toContain('mat-checkbox-disabled');
+      expect(inputElement.disabled).toBe(true);
+
+      testComponent.isDisabled = false;
+      fixture.detectChanges();
+
+      expect(checkboxInstance.disabled).toBe(false);
+      expect(checkboxNativeElement.classList).not.toContain('mat-checkbox-disabled');
+      expect(inputElement.tabIndex).toBe(0);
+      expect(inputElement.disabled).toBe(false);
+    });
+
+    it('should toggle checkbox ripple disabledness correctly', () => {
+      const labelElement = checkboxNativeElement.querySelector('label') as HTMLLabelElement;
+
+      testComponent.isDisabled = true;
+      fixture.detectChanges();
+      dispatchFakeEvent(labelElement, 'mousedown');
+      dispatchFakeEvent(labelElement, 'mouseup');
+      expect(checkboxNativeElement.querySelectorAll('.mat-ripple-element').length).toBe(0);
+
+      testComponent.isDisabled = false;
+      fixture.detectChanges();
+      dispatchFakeEvent(labelElement, 'mousedown');
+      dispatchFakeEvent(labelElement, 'mouseup');
+      expect(checkboxNativeElement.querySelectorAll('.mat-ripple-element').length).toBe(1);
+    });
+  });
+
   describe('with multiple checkboxes', () => {
     beforeEach(() => {
       fixture = TestBed.createComponent(MultipleCheckboxes);
@@ -1116,6 +1171,20 @@ class CheckboxWithTabIndex {
   isDisabled: boolean = false;
 }
 
+
+/** Simple test component that accesses MatCheckbox using ViewChild. */
+@Component({
+  template: `
+    <mat-checkbox></mat-checkbox>`,
+})
+class CheckboxUsingViewChild {
+  @ViewChild(MatCheckbox) checkbox;
+
+  set isDisabled(value: boolean) {
+    this.checkbox.disabled = value;
+  }
+}
+
 /** Simple test component with an aria-label set. */
 @Component({
   template: `<mat-checkbox aria-label="Super effective"></mat-checkbox>`

src/lib/checkbox/checkbox.ts

@@ -110,7 +110,7 @@ export const _MatCheckboxMixinBase =
     '[class.mat-checkbox-label-before]': 'labelPosition == "before"',
   },
   providers: [MAT_CHECKBOX_CONTROL_VALUE_ACCESSOR],
-  inputs: ['disabled', 'disableRipple', 'color', 'tabIndex'],
+  inputs: ['disableRipple', 'color', 'tabIndex'],
   encapsulation: ViewEncapsulation.None,
   changeDetection: ChangeDetectionStrategy.OnPush
 })
@@ -213,6 +213,20 @@ export class MatCheckbox extends _MatCheckboxMixinBase implements ControlValueAc
   }
   private _checked: boolean = false;
 
+  /**
+   * Whether the checkbox is disabled. This fully overrides the implementation provided by
+   * mixinDisabled, but the mixin is still required because mixinTabIndex requires it.
+   */
+  @Input()
+  get disabled() { return this._disabled; }
+  set disabled(value: any) {
+    if (value != this.disabled) {
+      this._disabled = value;
+      this._changeDetectorRef.markForCheck();
+    }
+  }
+  private _disabled: boolean = false;
+
   /**
    * Whether the checkbox is indeterminate. This is also known as "mixed" mode and can be used to
    * represent a checkbox with three states, e.g. a checkbox that represents a nested list of
@@ -267,7 +281,6 @@ export class MatCheckbox extends _MatCheckboxMixinBase implements ControlValueAc
   // Implemented as part of ControlValueAccessor.
   setDisabledState(isDisabled: boolean) {
     this.disabled = isDisabled;
-    this._changeDetectorRef.markForCheck();
   }
 
   _getAriaChecked(): 'true' | 'false' | 'mixed' {