Code-headers plugin rewrite (#37654)

Co-authored-by: Peter Bengtsson <peterbe@github.com>

lib/render-content/plugins/parse-info-string.js

@@ -7,17 +7,26 @@
 
 import { visit } from 'unist-util-visit'
 
-const matcher = (node) => node.type === 'code' && node.lang && node.meta
+const matcher = (node) => node.type === 'code' && node.lang
 
 export default function parseInfoString() {
   return (tree) => {
     visit(tree, matcher, (node) => {
       node.meta = strToObj(node.meta)
+
+      // Temporary, change {:copy} to ` copy` to avoid conflict in styles.
+      // We may end up enabling copy on all code examples later.
+      const copyTag = '{:copy}'
+      if (node.lang.includes(copyTag)) {
+        node.meta.copy = true
+        node.lang = node.lang.replace(copyTag, '')
+      }
     })
   }
 }
 
 function strToObj(str) {
+  if (!str) return {}
   return Object.fromEntries(
     str
       .split(/\s+/g)