More shadowrootcustomelementregistry attribute serialization tests

And another declarative shadow root test.

For whatwg/html#11892 and whatwg/html#11947.

Author: annevk

custom-elements/registries/template.window.js

@@ -17,9 +17,53 @@ test(() => {
 
 test(() => {
   const div = document.createElement("div");
+  div.setHTMLUnsafe(`<div><template shadowrootmode=open shadowrootserializable></template></div>`);
+  assert_equals(div.firstChild.firstChild, null);
+  assert_equals(div.firstChild.shadowRoot.customElementRegistry, customElements);
+  assert_equals(div.getHTML({ serializableShadowRoots: true }), "<div><template shadowrootmode=\"open\" shadowrootserializable=\"\"></template></div>");
+}, "Serializing a ShadowRoot with a global registry");
+
+test(() => {
+  const div = document.createElement("div");
+  div.setHTMLUnsafe(`<div><template shadowrootmode=open shadowrootcustomelementregistry shadowrootserializable></template></div>`);
+  const registry = new CustomElementRegistry();
+  registry.initialize(div.firstChild.shadowRoot);
+  assert_equals(div.firstChild.shadowRoot.customElementRegistry, registry);
+  assert_equals(div.getHTML({ serializableShadowRoots: true }), "<div><template shadowrootmode=\"open\" shadowrootserializable=\"\" shadowrootcustomelementregistry=\"\"></template></div>");
+}, "Serializing a ShadowRoot with a registry that differs from its host document");
+
+test(() => {
+  const div = document.implementation.createHTMLDocument().createElement("div");
+  assert_equals(div.customElementRegistry, null);
+  div.setHTMLUnsafe(`<div><template shadowrootmode=open shadowrootcustomelementregistry shadowrootserializable></template></div>`);
+  assert_equals(div.firstChild.shadowRoot.customElementRegistry, null);
+  assert_equals(div.getHTML({ serializableShadowRoots: true }), "<div><template shadowrootmode=\"open\" shadowrootserializable=\"\"></template></div>");
+}, "Serializing a ShadowRoot with a null registry with a null registry host document");
+
+test(() => {
+  const div = document.implementation.createHTMLDocument().createElement("div");
+  assert_equals(div.customElementRegistry, null);
   div.setHTMLUnsafe(`<div><template shadowrootmode=open shadowrootcustomelementregistry shadowrootserializable></template></div>`);
   const registry = new CustomElementRegistry();
   registry.initialize(div.firstChild.shadowRoot);
   assert_equals(div.firstChild.shadowRoot.customElementRegistry, registry);
   assert_equals(div.getHTML({ serializableShadowRoots: true }), "<div><template shadowrootmode=\"open\" shadowrootserializable=\"\" shadowrootcustomelementregistry=\"\"></template></div>");
-}, "Serializing a ShadowRoot with a registry that differs from its host");
+}, "Serializing a ShadowRoot with a registry with a null registry host document");
+
+test(() => {
+  const registry = new CustomElementRegistry();
+  const hostDocument = document.implementation.createHTMLDocument();
+  registry.initialize(hostDocument);
+  assert_equals(hostDocument.customElementRegistry, registry);
+  const host = hostDocument.createElement('div');
+  const shadow = host.attachShadow({ mode: "closed", serializable: true, customElementRegistry: null });
+  assert_equals(host.getHTML({ serializableShadowRoots: true }), `<template shadowrootmode="closed" shadowrootserializable="" shadowrootcustomelementregistry=""></template>`);
+}, "Serializing a ShadowRoot with a null registry with a scoped registry host document");
+
+test(() => {
+  const registry = new CustomElementRegistry();
+  const element = document.createElement('a-b', { customElementRegistry: registry });
+  element.setHTMLUnsafe(`<a-b><template shadowrootmode="open"></template></a-b>`);
+  assert_equals(element.firstChild.customElementRegistry, registry);
+  assert_equals(element.firstChild.shadowRoot.customElementRegistry, customElements);
+}, "A declarative shadow root gets its default registry from its node document");