fix(drag-drop): don't allow dragging using right mouse button (#12729)

Currently users can drag draggable elements using any mouse button. These changes limit dragging to the left button.

src/cdk-experimental/drag-drop/drag.spec.ts

@@ -12,7 +12,12 @@ import {
 } from '@angular/core';
 import {TestBed, ComponentFixture, fakeAsync, flush, tick} from '@angular/core/testing';
 import {DragDropModule} from './drag-drop-module';
-import {dispatchMouseEvent, dispatchTouchEvent} from '@angular/cdk/testing';
+import {
+  createMouseEvent,
+  dispatchEvent,
+  dispatchMouseEvent,
+  dispatchTouchEvent,
+} from '@angular/cdk/testing';
 import {Directionality} from '@angular/cdk/bidi';
 import {CdkDrag} from './drag';
 import {CdkDragDrop} from './drag-events';
@@ -95,6 +100,26 @@ describe('CdkDrag', () => {
 
           cleanup();
         }));
+
+      it('should not drag an element with the right mouse button', fakeAsync(() => {
+        const fixture = createComponent(StandaloneDraggable);
+        fixture.detectChanges();
+        const dragElement = fixture.componentInstance.dragElement.nativeElement;
+        const event = createMouseEvent('mousedown', 50, 100, 2);
+
+        expect(dragElement.style.transform).toBeFalsy();
+
+        dispatchEvent(dragElement, event);
+        fixture.detectChanges();
+
+        dispatchMouseEvent(document, 'mousemove', 50, 100);
+        fixture.detectChanges();
+
+        dispatchMouseEvent(document, 'mouseup');
+        fixture.detectChanges();
+
+        expect(dragElement.style.transform).toBeFalsy();
+      }));
     });
 
     describe('touch dragging', () => {

src/cdk-experimental/drag-drop/drag.ts

@@ -223,19 +223,23 @@ export class CdkDrag<T = any> implements OnDestroy {
   /** Handler for when the pointer is pressed down on the element or the handle. */
   private _pointerDown = (referenceElement: ElementRef<HTMLElement>,
                           event: MouseEvent | TouchEvent) => {
-    if (this._dragDropRegistry.isDragging(this)) {
+
+    const isDragging = this._dragDropRegistry.isDragging(this);
+
+    // Abort if the user is already dragging or is using a mouse button other than the primary one.
+    if (isDragging || (!this._isTouchEvent(event) && event.button !== 0)) {
       return;
     }
 
     const endedOrDestroyed = merge(this.ended, this._destroyed);
 
     this._dragDropRegistry.pointerMove
-        .pipe(takeUntil(endedOrDestroyed))
-        .subscribe(this._pointerMove);
+      .pipe(takeUntil(endedOrDestroyed))
+      .subscribe(this._pointerMove);
 
-        this._dragDropRegistry.pointerUp
-        .pipe(takeUntil(endedOrDestroyed))
-        .subscribe(this._pointerUp);
+    this._dragDropRegistry.pointerUp
+      .pipe(takeUntil(endedOrDestroyed))
+      .subscribe(this._pointerUp);
 
     this._dragDropRegistry.startDragging(this, event);
     this._initialContainer = this.dropContainer;

src/cdk/testing/event-objects.ts

@@ -7,7 +7,7 @@
  */
 
 /** Creates a browser MouseEvent with the specified options. */
-export function createMouseEvent(type: string, x = 0, y = 0) {
+export function createMouseEvent(type: string, x = 0, y = 0, button = 0) {
   const event = document.createEvent('MouseEvent');
 
   event.initMouseEvent(type,
@@ -23,7 +23,7 @@ export function createMouseEvent(type: string, x = 0, y = 0) {
     false, /* altKey */
     false, /* shiftKey */
     false, /* metaKey */
-    0, /* button */
+    button, /* button */
     null /* relatedTarget */);
 
   return event;