feat(autocomplete): add the ability to set a different panel connection element

Currently the autocomplete panel gets attached to the trigger element, however this can be inflexible in the cases where people have a custom input wrapper. These changes add the ability to have an autocomplete be attached to an element that is different from the trigger.

Fixes #11269.

Author: crisbeto

src/lib/autocomplete/autocomplete-module.ts

@@ -11,13 +11,18 @@ import {CommonModule} from '@angular/common';
 import {OverlayModule} from '@angular/cdk/overlay';
 import {MatOptionModule, MatCommonModule} from '@angular/material/core';
 import {MatAutocomplete} from './autocomplete';
-import {
-  MatAutocompleteTrigger,
-} from './autocomplete-trigger';
+import {MatAutocompleteTrigger} from './autocomplete-trigger';
+import {MatAutocompleteOrigin} from './autocomplete-origin';
 
 @NgModule({
   imports: [MatOptionModule, OverlayModule, MatCommonModule, CommonModule],
-  exports: [MatAutocomplete, MatOptionModule, MatAutocompleteTrigger, MatCommonModule],
-  declarations: [MatAutocomplete, MatAutocompleteTrigger],
+  exports: [
+    MatAutocomplete,
+    MatOptionModule,
+    MatAutocompleteTrigger,
+    MatAutocompleteOrigin,
+    MatCommonModule
+  ],
+  declarations: [MatAutocomplete, MatAutocompleteTrigger, MatAutocompleteOrigin],
 })
 export class MatAutocompleteModule {}

src/lib/autocomplete/autocomplete-origin.ts

@@ -0,0 +1,23 @@
+/**
+ * @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 {Directive, ElementRef} from '@angular/core';
+
+/**
+ * Directive applied to an element to make it usable
+ * as a connection point for an autocomplete panel.
+ */
+@Directive({
+  selector: '[matAutocompleteOrigin]',
+  exportAs: 'matAutocompleteOrigin',
+})
+export class MatAutocompleteOrigin {
+  constructor(
+      /** Reference to the element on which the directive is applied. */
+      public elementRef: ElementRef<HTMLElement>) { }
+}

src/lib/autocomplete/autocomplete-trigger.ts

@@ -45,6 +45,7 @@ import {MatFormField} from '@angular/material/form-field';
 import {Subscription, defer, fromEvent, merge, of as observableOf, Subject, Observable} from 'rxjs';
 import {MatAutocomplete} from './autocomplete';
 import {coerceBooleanProperty} from '@angular/cdk/coercion';
+import {MatAutocompleteOrigin} from './autocomplete-origin';
 
 
 /**
@@ -91,6 +92,7 @@ export function getMatAutocompleteMissingPanelError(): Error {
                'you\'re attempting to open it after the ngAfterContentInit hook.');
 }
 
+
 @Directive({
   selector: `input[matAutocomplete], textarea[matAutocomplete]`,
   host: {
@@ -143,6 +145,12 @@ export class MatAutocompleteTrigger implements ControlValueAccessor, OnDestroy {
   /** The autocomplete panel to be attached to this trigger. */
   @Input('matAutocomplete') autocomplete: MatAutocomplete;
 
+  /**
+   * Reference relative to which to position the autocomplete panel.
+   * Defaults to the autocomplete trigger element.
+   */
+  @Input('matAutocompleteConnectedTo') connectedTo: MatAutocompleteOrigin;
+
   /**
    * Whether the autocomplete is disabled. When disabled, the element will
    * act as a regular input and the user won't be able to open the panel.
@@ -562,6 +570,10 @@ export class MatAutocompleteTrigger implements ControlValueAccessor, OnDestroy {
   }
 
   private _getConnectedElement(): ElementRef {
+    if (this.connectedTo) {
+      return this.connectedTo.elementRef;
+    }
+
     return this._formField ? this._formField.getConnectedOverlayOrigin() : this._element;
   }
 

src/lib/autocomplete/autocomplete.md

@@ -6,9 +6,10 @@ Start by adding a regular `matInput` to your template. Let's assume you're using
 directive from `ReactiveFormsModule` to track the value of the input.
 
 > Note: It is possible to use template-driven forms instead, if you prefer. We use reactive forms
-in this example because it makes subscribing to changes in the input's value easy. For this example, be sure to
-import `ReactiveFormsModule` from `@angular/forms` into your `NgModule`. If you are unfamiliar with using reactive
-forms, you can read more about the subject in the [Angular documentation](https://angular.io/guide/reactive-forms).
+in this example because it makes subscribing to changes in the input's value easy. For this
+example, be sure to import `ReactiveFormsModule` from `@angular/forms` into your `NgModule`.
+If you are unfamiliar with using reactive forms, you can read more about the subject in the
+[Angular documentation](https://angular.io/guide/reactive-forms).
 
 *my-comp.html*
 ```html
@@ -61,8 +62,8 @@ option's first letter. We already have access to the built-in `valueChanges` Obs
 them through this filter. The resulting Observable, `filteredOptions`, can be added to the
 template in place of the `options` property using the `async` pipe.
 
-Below we are also priming our value change stream with an empty string so that the options are filtered by
-that value on init (before there are any value changes).
+Below we are also priming our value change stream with an empty string so that the options are
+filtered by that value on init (before there are any value changes).
 
 \*For optimal accessibility, you may want to consider adding text guidance on the page to explain
 filter criteria. This is especially helpful for screenreader users if you're using a non-standard
@@ -91,6 +92,29 @@ injection token.
 
 <!-- example(autocomplete-auto-active-first-option) -->
 
+### Attaching the autocomplete panel to a different element
+
+By default the autocomplete panel will be attached to your input element, however in some cases you
+may want it to attach to a different container element. You can change the element that the
+autocomplete is attached to using the `matAutocompleteOrigin` directive together with the
+`matAutocompleteConnectedTo` input:
+
+```html
+<div class="custom-wrapper-example" matAutocompleteOrigin #origin="matAutocompleteOrigin">
+  <input
+    matInput
+    [formControl]="myControl"
+    [matAutocomplete]="auto"
+    [matAutocompleteConnectedTo]="origin">
+</div>
+
+<mat-autocomplete #auto="matAutocomplete">
+  <mat-option *ngFor="let option of options" [value]="option">
+    {{ option }}
+  </mat-option>
+</mat-autocomplete>
+```
+
 ### Keyboard interaction
 - <kbd>DOWN_ARROW</kbd>: Next option becomes active.
 - <kbd>UP_ARROW</kbd>: Previous option becomes active.
@@ -115,5 +139,5 @@ injection token.
 The input for an autocomplete without text or labels should be given a meaningful label via
 `aria-label` or `aria-labelledby`.
 
-The autocomplete trigger is given `role="combobox"`. The trigger sets `aria-owns` to the autocomplete's
-id, and sets `aria-activedescendant` to the active option's id.
+The autocomplete trigger is given `role="combobox"`. The trigger sets `aria-owns` to the
+autocomplete's id, and sets `aria-activedescendant` to the active option's id.

src/lib/autocomplete/autocomplete.spec.ts

@@ -19,6 +19,7 @@ import {
   QueryList,
   ViewChild,
   ViewChildren,
+  Type,
 } from '@angular/core';
 import {
   async,
@@ -54,7 +55,7 @@ describe('MatAutocomplete', () => {
   let zone: MockNgZone;
 
   // Creates a test component fixture.
-  function createComponent(component: any, providers: Provider[] = []): ComponentFixture<any> {
+  function createComponent<T>(component: Type<T>, providers: Provider[] = []) {
     TestBed.configureTestingModule({
       imports: [
         MatAutocompleteModule,
@@ -78,7 +79,7 @@ describe('MatAutocomplete', () => {
       overlayContainerElement = oc.getContainerElement();
     })();
 
-    return TestBed.createComponent(component);
+    return TestBed.createComponent<T>(component);
   }
 
   afterEach(inject([OverlayContainer], (currentOverlayContainer: OverlayContainer) => {
@@ -1978,6 +1979,22 @@ describe('MatAutocomplete', () => {
     expect(event.source).toBe(fixture.componentInstance.autocomplete);
     expect(event.option.value).toBe('Puerto Rico');
   }));
+
+  it('should be able to set a custom panel connection element', () => {
+    const fixture = createComponent(AutocompleteWithDifferentOrigin);
+
+    fixture.detectChanges();
+    fixture.componentInstance.trigger.openPanel();
+    fixture.detectChanges();
+    zone.simulateZoneExit();
+
+    const overlayRect =
+        overlayContainerElement.querySelector('.cdk-overlay-pane')!.getBoundingClientRect();
+    const originRect = fixture.nativeElement.querySelector('.origin').getBoundingClientRect();
+
+    expect(Math.floor(overlayRect.top)).toBe(Math.floor(originRect.bottom),
+        'Expected autocomplete panel to align with the bottom of the new origin.');
+  });
 });
 
 @Component({
@@ -2315,3 +2332,35 @@ class AutocompleteWithNumberInputAndNgModel {
   selectedValue: number;
   values = [1, 2, 3];
 }
+
+
+@Component({
+  template: `
+    <div>
+      <mat-form-field>
+        <input
+          matInput
+          [matAutocomplete]="auto"
+          [matAutocompleteConnectedTo]="origin"
+          [(ngModel)]="selectedValue">
+      </mat-form-field>
+    </div>
+
+    <div
+      class="origin"
+      matAutocompleteOrigin
+      #origin="matAutocompleteOrigin"
+      style="margin-top: 50px">
+      Connection element
+    </div>
+
+    <mat-autocomplete #auto="matAutocomplete">
+      <mat-option *ngFor="let value of values" [value]="value">{{value}}</mat-option>
+    </mat-autocomplete>
+  `
+})
+class AutocompleteWithDifferentOrigin {
+  @ViewChild(MatAutocompleteTrigger) trigger: MatAutocompleteTrigger;
+  selectedValue: string;
+  values = ['one', 'two', 'three'];
+}