fix(overlay): clear duplicate overlay container coming in from the server

src/cdk/overlay/fullscreen-overlay-container.spec.ts

@@ -47,6 +47,9 @@ describe('FullscreenOverlayContainer', () => {
             createElement: function() {
               return document.createElement.apply(document, arguments);
             },
+            getElementsByClassName: function() {
+              return document.getElementsByClassName.apply(document, arguments);
+            }
           };
 
           return fakeDocument;

src/cdk/overlay/fullscreen-overlay-container.ts

@@ -66,13 +66,15 @@ export class FullscreenOverlayContainer extends OverlayContainer implements OnDe
 
   private _getEventName(): string | undefined {
     if (!this._fullScreenEventName) {
-      if (this._document.fullscreenEnabled) {
+      const _document = this._document as any;
+
+      if (_document.fullscreenEnabled) {
         this._fullScreenEventName = 'fullscreenchange';
-      } else if (this._document.webkitFullscreenEnabled) {
+      } else if (_document.webkitFullscreenEnabled) {
         this._fullScreenEventName = 'webkitfullscreenchange';
-      } else if ((this._document as any).mozFullScreenEnabled) {
+      } else if (_document.mozFullScreenEnabled) {
         this._fullScreenEventName = 'mozfullscreenchange';
-      } else if ((this._document as any).msFullscreenEnabled) {
+      } else if (_document.msFullscreenEnabled) {
         this._fullScreenEventName = 'MSFullscreenChange';
       }
     }
@@ -85,10 +87,12 @@ export class FullscreenOverlayContainer extends OverlayContainer implements OnDe
    * Only that element and its children are visible when in fullscreen mode.
    */
   getFullscreenElement(): Element {
-    return this._document.fullscreenElement ||
-           this._document.webkitFullscreenElement ||
-           (this._document as any).mozFullScreenElement ||
-           (this._document as any).msFullscreenElement ||
+    const _document = this._document as any;
+
+    return _document.fullscreenElement ||
+           _document.webkitFullscreenElement ||
+           _document.mozFullScreenElement ||
+           _document.msFullscreenElement ||
            null;
   }
 }

src/cdk/overlay/overlay-container.spec.ts

@@ -52,6 +52,16 @@ describe('OverlayContainer', () => {
     expect(containerElement.classList.contains('commander-shepard'))
         .toBe(false, 'Expected the overlay container not to have class "commander-shepard"');
   });
+
+  it('should ensure that there is only one overlay container on the page', () => {
+    const extraContainer = document.createElement('div');
+    extraContainer.classList.add('cdk-overlay-container');
+    document.body.appendChild(extraContainer);
+
+    overlayContainer.getContainerElement();
+
+    expect(document.querySelectorAll('.cdk-overlay-container').length).toBe(1);
+  });
 });
 
 /** Test-bed component that contains a TempatePortal and an ElementRef. */

src/cdk/overlay/overlay-container.ts

@@ -21,8 +21,11 @@ import {
 @Injectable({providedIn: 'root'})
 export class OverlayContainer implements OnDestroy {
   protected _containerElement: HTMLElement;
+  protected _document: Document;
 
-  constructor(@Inject(DOCUMENT) protected _document: any) {}
+  constructor(@Inject(DOCUMENT) document: any) {
+    this._document = document;
+  }
 
   ngOnDestroy() {
     if (this._containerElement && this._containerElement.parentNode) {
@@ -37,7 +40,10 @@ export class OverlayContainer implements OnDestroy {
    * @returns the container element
    */
   getContainerElement(): HTMLElement {
-    if (!this._containerElement) { this._createContainer(); }
+    if (!this._containerElement) {
+      this._createContainer();
+    }
+
     return this._containerElement;
   }
 
@@ -46,9 +52,16 @@ export class OverlayContainer implements OnDestroy {
    * with the 'cdk-overlay-container' class on the document body.
    */
   protected _createContainer(): void {
-    const container = this._document.createElement('div');
+    const containerClass = 'cdk-overlay-container';
+    const previousContainers = this._document.getElementsByClassName(containerClass);
 
-    container.classList.add('cdk-overlay-container');
+    // Remove any old containers. This can happen when transitioning from the server to the client.
+    for (let i = 0; i < previousContainers.length; i++) {
+      previousContainers[i].parentNode!.removeChild(previousContainers[i]);
+    }
+
+    const container = this._document.createElement('div');
+    container.classList.add(containerClass);
     this._document.body.appendChild(container);
     this._containerElement = container;
   }

tools/public_api_guard/cdk/overlay.d.ts

@@ -196,8 +196,8 @@ export interface OverlayConnectionPosition {
 
 export declare class OverlayContainer implements OnDestroy {
     protected _containerElement: HTMLElement;
-    protected _document: any;
-    constructor(_document: any);
+    protected _document: Document;
+    constructor(document: any);
     protected _createContainer(): void;
     getContainerElement(): HTMLElement;
     ngOnDestroy(): void;