Fix serializing mixed content

Fixes inikulin#333

Author: fb55

packages/parse5/lib/serializer/index.test.ts

@@ -1,5 +1,6 @@
 import * as assert from 'node:assert';
 import * as parse5 from 'parse5';
+import outdent from 'outdent';
 import { generateSerializerTests } from 'parse5-test-utils/utils/generate-serializer-tests.js';
 import { treeAdapters } from 'parse5-test-utils/utils/common.js';
 import type { Element } from 'parse5/dist/tree-adapters/default';
@@ -35,4 +36,18 @@ describe('serializer', () => {
             );
         });
     });
+
+    describe('Mixed content (GH-333)', () => {
+        it('should serialize mixed content', () => {
+            const input = outdent`
+              <svg><style>&lt;</style></svg>
+              <style>&lt;</style>
+
+              <svg><script>&lt;</script></svg>
+              <script>&lt;</script>
+            `;
+            const document = parse5.parse(input);
+            expect(parse5.serialize(document)).toContain(input);
+        });
+    });
 });

packages/parse5/lib/serializer/index.ts

@@ -74,7 +74,7 @@ type InternalOptions<T extends TreeAdapterTypeMap> = Required<SerializerOptions<
  */
 export function serialize<T extends TreeAdapterTypeMap = DefaultTreeAdapter.DefaultTreeAdapterMap>(
     node: T['parentNode'],
-    options: SerializerOptions<T>
+    options?: SerializerOptions<T>
 ): string {
     const opts = { treeAdapter: DefaultTreeAdapter, scriptingEnabled: true, ...options };
     return serializeChildNodes(node, opts);
@@ -108,7 +108,7 @@ function serializeElement<T extends TreeAdapterTypeMap>(node: T['element'], opti
     const tn = options.treeAdapter.getTagName(node);
 
     return `<${tn}${serializeAttributes(node, options)}>${
-        VOID_ELEMENTS.has(tn)
+        options.treeAdapter.getNamespaceURI(node) === NS.HTML && VOID_ELEMENTS.has(tn)
             ? ''
             : `${serializeChildNodes(
                   // Get container of the child nodes
@@ -165,7 +165,9 @@ function serializeTextNode<T extends TreeAdapterTypeMap>(node: T['textNode'], op
     const parent = treeAdapter.getParentNode(node);
     const parentTn = parent && treeAdapter.isElementNode(parent) && treeAdapter.getTagName(parent);
 
-    return parentTn && (UNESCAPED_TEXT.has(parentTn) || (options.scriptingEnabled && parentTn === $.NOSCRIPT))
+    return parentTn &&
+        treeAdapter.getNamespaceURI(parent) === NS.HTML &&
+        (UNESCAPED_TEXT.has(parentTn) || (options.scriptingEnabled && parentTn === $.NOSCRIPT))
         ? content
         : escapeString(content, false);
 }