fix(drag-drop): ignore enter predicate when returning item to its initial container

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

@@ -1579,6 +1579,46 @@ describe('CdkDrag', () => {
       expect(fixture.componentInstance.droppedSpy).not.toHaveBeenCalled();
     }));
 
+    it('should be able to move the element over a new container and return it to the initial ' +
+      'one, even if it no longer matches the enterPredicate', fakeAsync(() => {
+        const fixture = createComponent(ConnectedDropZones);
+        fixture.detectChanges();
+
+        const groups = fixture.componentInstance.groupedDragItems;
+        const dropZones = fixture.componentInstance.dropInstances.map(d => d.element.nativeElement);
+        const item = groups[0][1];
+        const initialRect = item.element.nativeElement.getBoundingClientRect();
+        const targetRect = groups[1][2].element.nativeElement.getBoundingClientRect();
+
+        fixture.componentInstance.dropInstances.first.enterPredicate = () => false;
+        fixture.detectChanges();
+
+        startDraggingViaMouse(fixture, item.element.nativeElement);
+
+        const placeholder = dropZones[0].querySelector('.cdk-drag-placeholder')!;
+
+        expect(placeholder).toBeTruthy();
+        expect(dropZones[0].contains(placeholder))
+            .toBe(true, 'Expected placeholder to be inside the first container.');
+
+        dispatchMouseEvent(document, 'mousemove', targetRect.left + 1, targetRect.top + 1);
+        fixture.detectChanges();
+
+        expect(dropZones[1].contains(placeholder))
+            .toBe(true, 'Expected placeholder to be inside second container.');
+
+        dispatchMouseEvent(document, 'mousemove', initialRect.left + 1, initialRect.top + 1);
+        fixture.detectChanges();
+
+        expect(dropZones[0].contains(placeholder))
+            .toBe(true, 'Expected placeholder to be back inside first container.');
+
+        dispatchMouseEvent(document, 'mouseup');
+        fixture.detectChanges();
+
+        expect(fixture.componentInstance.droppedSpy).not.toHaveBeenCalled();
+      }));
+
     it('should transfer the DOM element from one drop zone to another', fakeAsync(() => {
       const fixture = createComponent(ConnectedDropZones);
       fixture.detectChanges();

src/cdk/drag-drop/drag.ts

@@ -513,7 +513,7 @@ export class CdkDrag<T = any> implements AfterViewInit, OnDestroy {
     // This handles the case where two containers are connected one way and the user tries to
     // undo dragging an item into a new container.
     if (!newContainer && this.dropContainer !== this._initialContainer &&
-        this._initialContainer._canReturnItem(this, x, y)) {
+        this._initialContainer._canReturnItem(x, y)) {
       newContainer = this._initialContainer;
     }
 

src/cdk/drag-drop/drop-list-container.ts

@@ -60,7 +60,7 @@ export interface CdkDropListContainer<T = any> {
   _draggables: QueryList<CdkDrag>;
   _getSiblingContainerFromPosition(item: CdkDrag, x: number, y: number):
       CdkDropListContainer | null;
-  _canReturnItem(item: CdkDrag, x: number, y: number): boolean;
+  _canReturnItem(x: number, y: number): boolean;
 }
 
 /**

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

@@ -353,12 +353,11 @@ export class CdkDropList<T = any> implements OnInit, OnDestroy {
   /**
    * Checks whether an item that started in this container can be returned to it,
    * after it was moved out into another container.
-   * @param item Item that is being checked.
    * @param x Position of the item along the X axis.
    * @param y Position of the item along the Y axis.
    */
-  _canReturnItem(item: CdkDrag, x: number, y: number): boolean {
-    return isInsideClientRect(this._positionCache.self, x, y) && this.enterPredicate(item, this);
+  _canReturnItem(x: number, y: number): boolean {
+    return isInsideClientRect(this._positionCache.self, x, y);
   }
 
   /** Refreshes the position cache of the items and sibling containers. */