lit · aomarks · Mar 25, 2022 · Mar 23, 2022 · Mar 23, 2022 · Mar 23, 2022
@@ -0,0 +1,5 @@
+---
+'@lit-labs/ssr': minor
+---
+
+Adds HTMLElement.shadowRoot property to dom-shim.
@@ -46,6 +46,10 @@ export const getWindow = ({
         value,
       }));
     }
+    private _shadowRoot: null | ShadowRoot = null;
+    get shadowRoot() {
+      return this._shadowRoot;
+    }
     abstract attributeChangedCallback?(
       name: string,
       old: string | null,
@@ -60,8 +64,12 @@ export const getWindow = ({
     hasAttribute(name: string) {
       return attributesForElement(this).has(name);
     }
-    attachShadow() {
-      return {host: this};
+    attachShadow(init: ShadowRootInit) {
+      const shadowRoot = {host: this};
+      if (init && init.mode === 'open') {
+        this._shadowRoot = shadowRoot;
+      }
+      return shadowRoot;
     }
     getAttribute(name: string) {
       const value = attributesForElement(this).get(name);

@@ -4,5 +4,6 @@
  * SPDX-License-Identifier: BSD-3-Clause
  */
 
+import './lib/dom-shim_test.js';
 import './lib/render-lit_test.js';
 import './lib/module-loader_test.js';
@@ -0,0 +1,33 @@
+/**
+ * @license
+ * Copyright 2022 Google LLC
+ * SPDX-License-Identifier: BSD-3-Clause
+ */
+
+import {getWindow} from '../../lib/dom-shim.js';
+import {test} from 'uvu';
+import * as assert from 'uvu/assert';
+
+const window = getWindow({}) as unknown as Window;
+const {HTMLElement} = window.window;
+
+test('elements without an attached shadow root should expose a null value from the "shadowRoot" property', () => {
+  class UnattachedShadowRoot extends HTMLElement {}
+  const element = new UnattachedShadowRoot();
+  assert.is(element.shadowRoot, null);
+});
+test('elements defined with an open shadow root should expose it\'s shadow root from the "shadowRoot" property', () => {
+  class OpenShadowRoot extends HTMLElement {}
+  const element = new OpenShadowRoot();
+  const shadow = element.attachShadow({mode: 'open'});
+  assert.is(shadow, element.shadowRoot);
+  assert.is(shadow.host, element);
+});
+test('elements defined with a closed shadow root should expose a null value from the "shadowRoot" property', () => {
+  class ClosedShadowRoot extends HTMLElement {}
+  const element = new ClosedShadowRoot();
+  element.attachShadow({mode: 'closed'});
+  assert.is(element.shadowRoot, null);
+});
+
+test.run();