Refactor rowheaders table rewrite plugin (#37576)

lib/render-content/plugins/rewrite-for-rowheaders.js

@@ -0,0 +1,62 @@
+import { visitParents } from 'unist-util-visit-parents'
+
+/**
+ * Where it can mutate the AST to swap from:
+ *
+ *   <div class="rowheaders">
+ *
+ *     ...
+ *     <tbody>
+ *       <tr>
+ *         <td>...</td>
+ *         <td>...</td>
+ *     ...
+ *
+ *   </div>
+ *
+ * to:
+ *
+ *
+ *   <div class="rowheaders">
+ *
+ *     ...
+ *     <tbody>
+ *       <tr>
+ *         <td scope="row">...</td>
+ *         <td>...</td>
+ *     ...
+ *
+ *   </div>
+ *
+ * In other words, if contained in a `.rowheaders`, the *first* `<td>`
+ * in a `<tr>` should have `scope="row"`.
+ *
+ * */
+
+function matcher(node) {
+  return node.type === 'element' && node.tagName === 'td' && !('scope' in node.properties)
+}
+
+function insideRowheaders(ancestors) {
+  return ancestors.some(
+    (node) =>
+      node.properties &&
+      node.properties.className &&
+      node.properties.className.includes('rowheaders')
+  )
+}
+
+function visitor(node, ancestors) {
+  if (insideRowheaders(ancestors)) {
+    const tr = ancestors.at(-1)
+    if (!tr._scoped) {
+      tr._scoped = true
+      node.properties.scope = 'row'
+      node.tagName = 'th'
+    }
+  }
+}
+
+export default function rewriteForRowheaders() {
+  return (tree) => visitParents(tree, matcher, visitor)
+}