Add support for the shadow root clonable flag

This landed in the latest declarative shadow dom spec PR: whatwg/dom#892 and was discussed here: whatwg/dom#1137 This CL adds support for that, behind a new ShadowRootClonable flag. There was already a very basic test, but I added a few more cases. This should be fairly web compatible, but there is a risk since with this feature enabled, declarative shadow roots in the main document (as opposed to in a <template> element) will now be cloned. I will launch this feature carefully. Safari has already shipped, and Gecko has implemented this and plans to ship soon. Fixed: 1510466 Change-Id: Ie25b72f369ca0542555f91010b0f22d295403728
web-platform-tests · Jan 26, 2024 · 12c3cce · 12c3cce
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diff --git a/shadow-dom/declarative/clonable.window.js b/shadow-dom/declarative/clonable.window.js
diff --git a/shadow-dom/shadow-root-clonable.html b/shadow-dom/shadow-root-clonable.html
@@ -0,0 +1,47 @@
+<!DOCTYPE html>
+<title>Shadow root clonable flag</title>
+<link rel='author' href='mailto:krosylight@mozilla.com'>
+<link rel='author' href='mailto:masonf@chromium.org'>
+<link rel='help' href='https://dom.spec.whatwg.org/#shadowroot-clonable'>
+<script src='/resources/testharness.js'></script>
+<script src='/resources/testharnessreport.js'></script>
+
+<body>
+<script>
+test(() => {
+ const div = document.createElement("div");
+ const root = div.attachShadow({ mode: "open", clonable: true });
+ root.appendChild(document.createElement("input"));
+ assert_true(root.clonable, "clonable attribute");
+
+ const cloned = div.cloneNode(true);
+ assert_equals(cloned.shadowRoot.children.length, 1, "children count");
+ assert_equals(cloned.shadowRoot.children[0].localName, "input", "children content");
+}, "attachShadow with clonable: true");
+
+for (clonable of [false, undefined]) {
+ test(() => {
+ const div = document.createElement("div");
+ const root = div.attachShadow({ mode: "open", clonable });
+ root.appendChild(document.createElement("input"));
+ assert_false(root.clonable, "clonable attribute");
+
+ const cloned = div.cloneNode(true);
+ assert_true(!cloned.shadowRoot, "shadow should not be cloned");
+ }, `attachShadow with clonable: ${clonable}`);
+}
+
+test(() => {
+ const div = document.createElement("div");
+ div.setHTMLUnsafe('<div><template shadowrootmode=open><input></template></div>');
+ const root = div.firstElementChild.shadowRoot;
+ assert_true(!!root);
+ assert_true(root.clonable, "clonable is automatically true for declarative shadow root");
+
+ const cloned = div.cloneNode(true);
+ const clonedRoot = cloned.firstElementChild.shadowRoot;
+ assert_true(!!clonedRoot);
+ assert_equals(clonedRoot.children.length, 1, "children count");
+ assert_equals(clonedRoot.children[0].localName, "input", "children content");
+}, "declarative shadow roots get clonable: true automatically");
+</script>