fix(form-field): outline gap not calculated when appearance is provided through DI

Fixes the outline gap not being calculated if the `appearance` is set through the default options, because it doesn't go through the setter and we're not guaranteed for the `MutationObserver` callback to fire at the right time.

Fixes #12765.

Author: crisbeto

src/lib/form-field/form-field.ts

@@ -144,12 +144,12 @@ export class MatFormField extends _MatFormFieldMixinBase
 
   /** The form-field appearance style. */
   @Input()
-  get appearance(): MatFormFieldAppearance {
-    return this._appearance || this._defaultOptions && this._defaultOptions.appearance || 'legacy';
-  }
+  get appearance(): MatFormFieldAppearance { return this._appearance; }
   set appearance(value: MatFormFieldAppearance) {
     const oldValue = this._appearance;
-    this._appearance = value;
+
+    this._appearance = value || (this._defaults && this._defaults.appearance) || 'legacy';
+
     if (this._appearance === 'outline' && oldValue !== value) {
       // @breaking-change 7.0.0 Remove this check and else block once _ngZone is required.
       if (this._ngZone) {
@@ -245,8 +245,8 @@ export class MatFormField extends _MatFormFieldMixinBase
       private _changeDetectorRef: ChangeDetectorRef,
       @Optional() @Inject(MAT_LABEL_GLOBAL_OPTIONS) labelOptions: LabelOptions,
       @Optional() private _dir: Directionality,
-      @Optional() @Inject(MAT_FORM_FIELD_DEFAULT_OPTIONS) private _defaultOptions:
-          MatFormFieldDefaultOptions,
+      @Optional() @Inject(MAT_FORM_FIELD_DEFAULT_OPTIONS)
+          private _defaults: MatFormFieldDefaultOptions,
       // @breaking-change 7.0.0 _platform, _ngZone and _animationMode to be made required.
       private _platform?: Platform,
       private _ngZone?: NgZone,
@@ -256,6 +256,9 @@ export class MatFormField extends _MatFormFieldMixinBase
     this._labelOptions = labelOptions ? labelOptions : {};
     this.floatLabel = this._labelOptions.float || 'auto';
     this._animationsEnabled = _animationMode !== 'NoopAnimations';
+
+    // Set the default through here so we invoke the setter on the first run.
+    this.appearance = (_defaults && _defaults.appearance) ? _defaults.appearance : 'legacy';
   }
 
   /**

src/lib/input/input.spec.ts

@@ -1,6 +1,11 @@
 import {Platform, PlatformModule} from '@angular/cdk/platform';
-import {createFakeEvent, dispatchFakeEvent, wrappedErrorMessage} from '@angular/cdk/testing';
-import {ChangeDetectionStrategy, Component, ViewChild, Type, Provider} from '@angular/core';
+import {
+  createFakeEvent,
+  dispatchFakeEvent,
+  wrappedErrorMessage,
+  MockNgZone,
+} from '@angular/cdk/testing';
+import {ChangeDetectionStrategy, Component, ViewChild, Type, Provider, NgZone} from '@angular/core';
 import {ComponentFixture, fakeAsync, flush, TestBed} from '@angular/core/testing';
 import {
   FormControl,
@@ -28,10 +33,10 @@ import {
 } from '@angular/material/form-field';
 import {By} from '@angular/platform-browser';
 import {BrowserAnimationsModule} from '@angular/platform-browser/animations';
-import {MatInputModule} from './index';
-import {MatInput} from './input';
 import {MatStepperModule} from '@angular/material/stepper';
 import {MatTabsModule} from '@angular/material/tabs';
+import {MatInputModule} from './index';
+import {MatInput} from './input';
 import {MatTextareaAutosize} from './autosize';
 
 describe('MatInput without forms', () => {
@@ -1170,6 +1175,35 @@ describe('MatInput with appearance', () => {
     expect(parseInt(outlineGap.style.width)).toBeFalsy();
   }));
 
+  it('should calculate the gaps if the default appearance is provided through DI', fakeAsync(() => {
+    fixture.destroy();
+    TestBed.resetTestingModule();
+
+    let zone: MockNgZone;
+    const labelFixture = createComponent(MatInputWithLabel, [
+      {
+        provide: MAT_FORM_FIELD_DEFAULT_OPTIONS,
+        useValue: {appearance: 'outline'}
+      },
+      {
+        provide: NgZone,
+        useFactory: () => zone = new MockNgZone()
+      }
+    ]);
+
+    labelFixture.detectChanges();
+    zone!.simulateZoneExit();
+    flush();
+    labelFixture.detectChanges();
+
+    const wrapperElement = labelFixture.nativeElement;
+    const outlineStart = wrapperElement.querySelector('.mat-form-field-outline-start');
+    const outlineGap = wrapperElement.querySelector('.mat-form-field-outline-gap');
+
+    expect(parseInt(outlineStart.style.width)).toBeGreaterThan(0);
+    expect(parseInt(outlineGap.style.width)).toBeGreaterThan(0);
+  }));
+
 });
 
 describe('MatFormField default options', () => {
@@ -1586,6 +1620,16 @@ class MatInputOnPush {
 })
 class MatInputWithReadonlyInput {}
 
+@Component({
+  template: `
+    <mat-form-field>
+      <mat-label>Label</mat-label>
+      <input matInput>
+    </mat-form-field>
+  `
+})
+class MatInputWithLabel {}
+
 @Component({
   template: `
     <mat-form-field [floatLabel]="floatLabel">