Scope non-scoped (global) registries to a single document

This preserves existing behavior. We throw exceptions in certain corner cases to give us some wiggle room in the future to change some of this around.

Corresponding HTML PR: TODO

Tests: web-platform-tests/wpt#53791.

Fixes #1390.

Author: annevk

dom.bs

@@ -4920,10 +4920,18 @@ and an optional <a for=/>document</a> <dfn export for="clone a node"><var>docume
 
   <dl class=switch>
    <dt>{{Document}}
-   <dd><p>Set <var>copy</var>'s <a for=Document>encoding</a>, <a for=Document>content type</a>,
-   <a for=Document>URL</a>, <a for=Document>origin</a>, <a for=Document>type</a>,
-   <a for=Document>mode</a>, <a for=Document>allow declarative shadow roots</a>, and
-   <a for=Document>custom element registry</a> to those of <var>node</var>.
+   <dd>
+    <ol>
+     <li><p>Set <var>copy</var>'s <a for=Document>encoding</a>, <a for=Document>content type</a>,
+     <a for=Document>URL</a>, <a for=Document>origin</a>, <a for=Document>type</a>,
+     <a for=Document>mode</a>, and <a for=Document>allow declarative shadow roots</a>, to those of
+     <var>node</var>.
+
+     <li><p>If <var>node</var>'s <a for=Document>custom element registry</a>'s
+     <a for=CustomElementRegistry>is scoped</a> is true, then set <var>copy</var>'s
+     <a for=Document>custom element registry</a> to <var>node</var>'s
+     <a for=Document>custom element registry</a>.
+    </ol>
 
    <dt>{{DocumentType}}
    <dd><p>Set <var>copy</var>'s <a for=DocumentType>name</a>, <a>public ID</a>, and
@@ -5774,6 +5782,7 @@ method steps are to return the <a>list of elements with class names <var>classNa
 <p class=note>The HTML Standard will, e.g., define that for <code>html</code> and the
 <a>HTML namespace</a>, the {{HTMLHtmlElement}} interface is used. [[!HTML]]
 
+<div algorithm>
 <p>The
 <dfn method for=Document><code>createElement(<var>localName</var>, <var>options</var>)</code></dfn>
 method steps are:
@@ -5795,7 +5804,9 @@ method steps are:
  <li><p>Return the result of <a>creating an element</a> given <a>this</a>, <var>localName</var>,
  <var>namespace</var>, null, <var>is</var>, true, and <var>registry</var>.
 </ol>
+</div>
 
+<div algorithm>
 <p>The <dfn noexport>internal <code>createElementNS</code> steps</dfn>, given <var>document</var>,
 <var>namespace</var>, <var>qualifiedName</var>, and <var>options</var>, are as follows:
 
@@ -5811,13 +5822,17 @@ method steps are:
  <var>localName</var>, <var>namespace</var>, <var>prefix</var>, <var>is</var>, true, and
  <var>registry</var>.
 </ol>
+</div>
 
+<div algorithm>
 <p>The
 <dfn method for=Document><code>createElementNS(<var>namespace</var>, <var>qualifiedName</var>, <var>options</var>)</code></dfn>
 method steps are to return the result of running the
 <a>internal <code>createElementNS</code> steps</a>, given <a>this</a>, <var>namespace</var>,
 <var>qualifiedName</var>, and <var>options</var>.
+</div>
 
+<div algorithm>
 <p>To <dfn>flatten element creation options</dfn>, given a string or {{ElementCreationOptions}}
 dictionary <var>options</var> and a <a for=/>document</a> <var>document</var>:
 
@@ -5833,6 +5848,10 @@ dictionary <var>options</var> and a <a for=/>document</a> <var>document</var>:
    <li><p>If <var>options</var>["{{ElementCreationOptions/customElementRegistry}}"]
    <a for=map>exists</a>, then set <var>registry</var> to it.
 
+   <li><p>If <var>registry</var>'s <a for=CustomElementRegistry>is scoped</a> is false and
+   <var>registry</var> is not <var>document</var>'s <a for=Document>custom element registry</a>,
+   then <a>throw</a> a "{{NotSupportedError!!exception}}" {{DOMException}}.
+
    <li><p>If <var>options</var>["{{ElementCreationOptions/is}}"] <a for=map>exists</a>, then set
    <var>is</var> to it.
 
@@ -5848,6 +5867,7 @@ dictionary <var>options</var> and a <a for=/>document</a> <var>document</var>:
 
 <p class=note>{{Document/createElement()}} and {{Document/createElementNS()}}'s <var>options</var>
 parameter is allowed to be a string for web compatibility.
+</div>
 
 <p>The <dfn method for=Document><code>createDocumentFragment()</code></dfn> method steps are to
 return a new {{DocumentFragment}} <a for=/>node</a> whose <a for=Node>node document</a> is
@@ -5944,6 +5964,10 @@ method steps are:
 
    <li><p>If <var>options</var>["{{ImportNodeOptions/customElementRegistry}}"]
    <a for=map>exists</a>, then set <var>registry</var> to it.
+
+   <li><p>If <var>registry</var>'s <a for=CustomElementRegistry>is scoped</a> is false and
+   <var>registry</var> is not <a>this</a>'s <a for=Document>custom element registry</a>, then
+   <a>throw</a> a "{{NotSupportedError!!exception}}" {{DOMException}}.
   </ol>
 
  <li><p>If <var>registry</var> is null, then set <var>registry</var> to the result of
@@ -5961,6 +5985,7 @@ method steps are:
 algorithm is passed <var>node</var> and <var>oldDocument</var>, as indicated in the <a>adopt</a>
 algorithm.
 
+<div algorithm>
 <p>To <dfn export id=concept-node-adopt>adopt</dfn> a <var>node</var> into a <var>document</var>, run
 these steps:
 
@@ -5974,16 +5999,44 @@ these steps:
   <p>If <var>document</var> is not <var>oldDocument</var>:
 
   <ol>
+   <li><p>Let <var>documentRegistry</var> be <var>document</var>'s
+   <a for=Document>custom element registry</a>.
+
+   <li><p>Let <var>documentHasGlobalRegistry</var> be true if <var>documentRegistry</var> is
+   non-null and <var>documentRegistry</var>'s <a for=CustomElementRegistry>is scoped</a> is false;
+   otherwise false.
+
    <li>
     <p>For each <var>inclusiveDescendant</var> in <var>node</var>'s
     <a>shadow-including inclusive descendants</a>:
 
     <ol>
      <li><p>Set <var>inclusiveDescendant</var>'s <a for=Node>node document</a> to <var>document</var>.
 
-     <li><p>If <var>inclusiveDescendant</var> is an <a for=/>element</a>, then set the
-     <a for=Node>node document</a> of each <a>attribute</a> in <var>inclusiveDescendant</var>'s
-     <a for=Element>attribute list</a> to <var>document</var>.
+     <li>
+      <p>If <var>inclusiveDescendant</var> is a <a for=/>shadow root</a>:
+
+      <ol>
+       <li><p>If <var>inclusiveDescendant</var>'s <a for=ShadowRoot>custom element registry</a> is
+       non-null, <var>inclusiveDescendant</var>'s <a for=ShadowRoot>custom element registry</a>'s
+       <a for=CustomElementRegistry>is scoped</a> is false, and <var>documentHasGlobalRegistry</var>
+       is true, then set <var>inclusiveDescendant</var>'s
+       <a for=ShadowRoot>custom element registry</a> to <var>documentRegistry</var>.
+      </ol>
+
+     <li>
+      <p>Otherwise, if <var>inclusiveDescendant</var> is an <a for=/>element</a>:
+
+      <ol>
+       <li><p>Set the <a for=Node>node document</a> of each <a>attribute</a> in
+       <var>inclusiveDescendant</var>'s <a for=Element>attribute list</a> to <var>document</var>.
+
+       <li><p>If <var>inclusiveDescendant</var>'s <a for=Element>custom element registry</a> is
+       non-null, <var>inclusiveDescendant</var>'s <a for=Element>custom element registry</a>'s
+       <a for=CustomElementRegistry>is scoped</a> is false, and <var>documentHasGlobalRegistry</var>
+       is true, then set <var>inclusiveDescendant</var>'s <a for=Element>custom element registry</a>
+       to <var>documentRegistry</var>.
+      </ol>
     </ol>
 
    <li><p>For each <var>inclusiveDescendant</var> in <var>node</var>'s
@@ -5997,7 +6050,9 @@ these steps:
    <a>adopting steps</a> with <var>inclusiveDescendant</var> and <var>oldDocument</var>.
   </ol>
 </ol>
+</div>
 
+<div algorithm>
 <p>The <dfn method for=Document><code>adoptNode(<var>node</var>)</code></dfn> method steps are:
 
 <ol>
@@ -6014,6 +6069,7 @@ these steps:
 
  <li><p>Return <var>node</var>.
 </ol>
+</div>
 
 <hr>
 
@@ -7515,8 +7571,17 @@ are:
 <ol>
  <li><p>Let <var>registry</var> be <a>this</a>'s <a for=Element>custom element registry</a>.
 
- <li><p>If <var>init</var>["{{ShadowRootInit/customElementRegistry}}"] is non-null, then set
- <var>registry</var> to it.
+ <li>
+  <p>If <var>init</var>["{{ShadowRootInit/customElementRegistry}}"] is non-null:
+
+  <ol>
+   <li><p>Set <var>registry</var> to <var>init</var>["{{ShadowRootInit/customElementRegistry}}"].
+
+   <li><p>If <var>registry</var>'s <a for=CustomElementRegistry>is scoped</a> is false and
+   <var>registry</var> is not <a>this</a>'s <a>node document</a>'s
+   <a for=Document>custom element registry</a>, then <a>throw</a> a
+   "{{NotSupportedError!!exception}}" {{DOMException}}.
+  </ol>
 
  <li><p>Run <a>attach a shadow root</a> with <a>this</a>,
  <var>init</var>["{{ShadowRootInit/mode}}"], <var>init</var>["{{ShadowRootInit/clonable}}"],