fix(material/form-field): not visually disabled if form control is disabled without emitting an event (#26088)

Fixes that the form field wasn't visually disabled if the consumer disables it using `emitEvents: false`.

Fixes #26057.

Author: crisbeto

src/material/input/input.spec.ts

@@ -1188,7 +1188,7 @@ describe('MatMdcInput with forms', () => {
 
   describe('custom error behavior', () => {
     it('should display an error message when a custom error matcher returns true', fakeAsync(() => {
-      let fixture = createComponent(MatInputWithCustomErrorStateMatcher);
+      let fixture = createComponent(InputInFormGroup);
       fixture.detectChanges();
 
       let component = fixture.componentInstance;
@@ -1356,6 +1356,18 @@ describe('MatMdcInput with forms', () => {
 
     expect(notch.style.width).toBeTruthy();
   }));
+
+  it('should mark the form field as disabled when a group is disabled with emitEvent: false', fakeAsync(() => {
+    const fixture = createComponent(InputInFormGroup);
+    fixture.detectChanges();
+
+    const mdcTextField = fixture.nativeElement.querySelector('.mdc-text-field');
+    expect(mdcTextField.classList).not.toContain('mdc-text-field--disabled');
+
+    fixture.componentInstance.formGroup.disable({emitEvent: false});
+    fixture.detectChanges();
+    expect(mdcTextField.classList).toContain('mdc-text-field--disabled');
+  }));
 });
 
 describe('MatFormField default options', () => {
@@ -1793,7 +1805,7 @@ class MatInputWithFormErrorMessages {
     </form>
   `,
 })
-class MatInputWithCustomErrorStateMatcher {
+class InputInFormGroup {
   formGroup = new FormGroup({
     name: new FormControl('', [Validators.required, Validators.pattern(/valid value/)]),
   });

src/material/input/input.ts

@@ -160,9 +160,6 @@ export class MatInput
    */
   @Input()
   get disabled(): boolean {
-    if (this.ngControl && this.ngControl.disabled !== null) {
-      return this.ngControl.disabled;
-    }
     return this._disabled;
   }
   set disabled(value: BooleanInput) {
@@ -356,6 +353,15 @@ export class MatInput
       // error triggers that we can't subscribe to (e.g. parent form submissions). This means
       // that whatever logic is in here has to be super lean or we risk destroying the performance.
       this.updateErrorState();
+
+      // Since the input isn't a `ControlValueAccessor`, we don't have a good way of knowing when
+      // the disabled state has changed. We can't use the `ngControl.statusChanges`, because it
+      // won't fire if the input is disabled with `emitEvents = false`, despite the input becoming
+      // disabled.
+      if (this.ngControl.disabled !== null && this.ngControl.disabled !== this.disabled) {
+        this.disabled = this.ngControl.disabled;
+        this.stateChanges.next();
+      }
     }
 
     // We need to dirty-check the native element's value, because there are some cases where