fix: avoid registering lit-virtualizer globally

tools/grid/src/Grid.ts

@@ -16,9 +16,8 @@ import {
     TemplateResult,
 } from '@spectrum-web-components/base';
 import { property } from '@spectrum-web-components/base/src/decorators.js';
-import { LitVirtualizer } from '@lit-labs/virtualizer';
+import { LitVirtualizer } from './LitVirtualizer.js';
 import { grid } from '@lit-labs/virtualizer/layouts/grid.js';
-
 import styles from './grid.css.js';
 import { GridController } from './GridController.js';
 

tools/grid/src/GridController.ts

@@ -9,15 +9,14 @@ the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR REPRESENTA
 OF ANY KIND, either express or implied. See the License for the specific language
 governing permissions and limitations under the License.
 */
-import type { ReactiveController } from 'lit';
+import type { ReactiveController, ReactiveElement } from 'lit';
 
 import { ResizeController } from '@lit-labs/observers/resize_controller.js';
 import { RovingTabindexController } from '@spectrum-web-components/reactive-controllers/src/RovingTabindex.js';
 import {
     RangeChangedEvent,
     VisibilityChangedEvent,
 } from '@lit-labs/virtualizer/Virtualizer.js';
-import type { LitVirtualizer } from '@lit-labs/virtualizer';
 
 interface ItemSize {
     width: number;
@@ -27,7 +26,7 @@ interface ItemSize {
 export class GridController<T extends HTMLElement>
     implements ReactiveController
 {
-    host!: LitVirtualizer;
+    host!: ReactiveElement;
 
     resizeController!: ResizeController;
 
@@ -61,7 +60,7 @@ export class GridController<T extends HTMLElement>
     _last = 0;
 
     constructor(
-        host: LitVirtualizer,
+        host: ReactiveElement,
         {
             elements,
             itemSize,
@@ -151,7 +150,7 @@ export class GridController<T extends HTMLElement>
                 });
             });
         };
-        const scrollToFirst = (): void => this.host.scrollToIndex(0);
+        const scrollToFirst = (): void => (this.host as any).scrollToIndex(0);
         const focusIntoGrid = (): void => {
             this.focus();
             this.host.tabIndex = -1;

tools/grid/src/LitVirtualizer.ts

@@ -0,0 +1,27 @@
+/*
+Copyright 2020 Adobe. All rights reserved.
+This file is licensed to you under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License. You may obtain a copy
+of the License at http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software distributed under
+the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR REPRESENTATIONS
+OF ANY KIND, either express or implied. See the License for the specific language
+governing permissions and limitations under the License.
+*/
+
+// @lit-labs/virtualizer combines defining the LitVirtualizer class with defining `lit-virtualizer` in the global registry.
+// Grid extends LitVirtualizer and doesn't need the tag, which can conflict with other uses of lit-virtualizer in the same document.
+// This is a hack to keep lit-virtualizer from registering globally.
+
+const oldDefine = customElements.define;
+customElements.define = (name, constructor) => {
+    if (name === 'lit-virtualizer') return;
+    oldDefine.call(customElements, name, constructor);
+};
+
+const { LitVirtualizer } = await import('@lit-labs/virtualizer');
+
+customElements.define = oldDefine;
+
+export { LitVirtualizer };

tools/grid/test/grid.test.ts

@@ -251,4 +251,24 @@ describe('Grid', () => {
 
         expect(el.selected).to.deep.equal([{ id: 4 }]);
     });
+    it('does not claim lit-virtualizer on the global registry', async () => {
+        const test = await fixture<HTMLDivElement>(
+            html`
+                <div>${Default()}</div>
+            `
+        );
+        const el = test.querySelector('sp-grid') as Grid;
+
+        await elementUpdated(el);
+
+        customElements.define('lit-virtualizer', class extends HTMLElement {});
+
+        // make sure we also don't prevent *any* registration of lit-virtualizer
+        expect(() => {
+            customElements.define(
+                'lit-virtualizer',
+                class extends HTMLElement {}
+            );
+        }).to.throw();
+    });
 });