fix(autocomplete): reopen panel on input click

Currently if the user clicks an autocomplete to open it, selects an option and then clicks again, the panel won't open, because we use `focus` and the input was focused already. These changes add an extra `click` listener so the panel can reopen.

Fixes #15177.

Author: crisbeto

src/material/autocomplete/autocomplete-trigger.ts

@@ -119,6 +119,7 @@ export function getMatAutocompleteMissingPanelError(): Error {
     '(blur)': '_onTouched()',
     '(input)': '_handleInput($event)',
     '(keydown)': '_handleKeydown($event)',
+    '(click)': 'openPanel()',
   },
   exportAs: 'matAutocompleteTrigger',
   providers: [MAT_AUTOCOMPLETE_VALUE_ACCESSOR]
@@ -270,8 +271,10 @@ export class MatAutocompleteTrigger implements ControlValueAccessor, AfterViewIn
 
   /** Opens the autocomplete suggestion panel. */
   openPanel(): void {
-    this._attachOverlay();
-    this._floatLabel();
+    if (!this.panelOpen) {
+      this._attachOverlay();
+      this._floatLabel();
+    }
   }
 
   /** Closes the autocomplete suggestion panel. */

src/material/autocomplete/autocomplete.spec.ts

@@ -516,6 +516,29 @@ describe('MatAutocomplete', () => {
       expect(input.getAttribute('aria-haspopup')).toBe('false');
     });
 
+    it('should close the panel when pressing escape', fakeAsync(() => {
+      const trigger = fixture.componentInstance.trigger;
+
+      input.focus();
+      flush();
+      fixture.detectChanges();
+
+      expect(document.activeElement).toBe(input, 'Expected input to be focused.');
+      expect(trigger.panelOpen).toBe(true, 'Expected panel to be open.');
+
+      trigger.closePanel();
+      fixture.detectChanges();
+
+      expect(document.activeElement).toBe(input, 'Expected input to continue to be focused.');
+      expect(trigger.panelOpen).toBe(false, 'Expected panel to be closed.');
+
+      input.click();
+      flush();
+      fixture.detectChanges();
+
+      expect(trigger.panelOpen).toBe(true, 'Expected panel to reopen on click.');
+    }));
+
   });
 
   it('should not close the panel when clicking on the input', fakeAsync(() => {