fix(autocomplete): handle attaching autocomplete to a number input (#9672)

Fixes the value being typed inside an `input[type="number"]` getting assigned to the model as a string. Normally this is handled by the `NumberValueAccessor` from the forms module, however the autocomplete is its own value accessor and as such has to handle it on its own.

Fixes #9628.

src/lib/autocomplete/autocomplete-trigger.ts

@@ -305,7 +305,15 @@ export class MatAutocompleteTrigger implements ControlValueAccessor, OnDestroy {
     // event on focus/blur/load if the input has a placeholder. See:
     // https://connect.microsoft.com/IE/feedback/details/885747/
     if (this._canOpen() && document.activeElement === event.target) {
-      this._onChange((event.target as HTMLInputElement).value);
+      let target = event.target as HTMLInputElement;
+      let value: number | string | null = target.value;
+
+      // Based on `NumberValueAccessor` from forms.
+      if (target.type === 'number') {
+        value = value == '' ? null : parseFloat(value);
+      }
+
+      this._onChange(value);
       this.openPanel();
     }
   }

src/lib/autocomplete/autocomplete.spec.ts

@@ -1639,6 +1639,17 @@ describe('MatAutocomplete', () => {
       expect(trigger.panelOpen).toBe(false, 'Expected panel to be closed.');
     }));
 
+    it('should handle autocomplete being attached to number inputs', fakeAsync(() => {
+      const fixture = createComponent(AutocompleteWithNumberInputAndNgModel);
+      fixture.detectChanges();
+      const input = fixture.debugElement.query(By.css('input')).nativeElement;
+
+      typeInElement('1337', input);
+      fixture.detectChanges();
+
+      expect(fixture.componentInstance.selectedValue).toBe(1337);
+    }));
+
   });
 
   it('should have correct width when opened', () => {
@@ -2072,3 +2083,20 @@ class AutocompleteWithSelectEvent {
 class PlainAutocompleteInputWithFormControl {
   formControl = new FormControl();
 }
+
+
+@Component({
+  template: `
+    <mat-form-field>
+      <input type="number" matInput [matAutocomplete]="auto" [(ngModel)]="selectedValue">
+    </mat-form-field>
+
+    <mat-autocomplete #auto="matAutocomplete">
+      <mat-option *ngFor="let value of values" [value]="value">{{value}}</mat-option>
+    </mat-autocomplete>
+  `
+})
+class AutocompleteWithNumberInputAndNgModel {
+  selectedValue: number;
+  values = [1, 2, 3];
+}