feat(src): writes plugin

package.json

@@ -50,6 +50,7 @@
     "@types/dedent": "^0.7.0",
     "@types/jest": "^26.0.22",
     "@types/node": "^14.14.41",
+    "@types/unist": "^2.0.3",
     "commitizen": "^4.2.3",
     "cz-conventional-changelog": "^3.3.0",
     "dedent": "^0.7.0",
@@ -111,5 +112,8 @@
         "type": "test"
       }
     ]
+  },
+  "dependencies": {
+    "unist-util-visit": "^3.0.0"
   }
 }

src/index.ts

@@ -1 +1,48 @@
-export const x = 42
+import { Node, Parent } from 'unist'
+import { visit } from 'unist-util-visit'
+
+function rehypeCodeTitles() {
+  return (tree: Node) => visit(tree, 'element', visitor)
+
+  function visitor(
+    node: Node,
+    index: number | null,
+    parent: Parent | null
+  ): void {
+    if (!parent || node.tagName !== 'pre') {
+      return
+    }
+
+    const pre = node
+    const code = Array.isArray(pre.children) ? pre.children[0] : pre.children
+    const className: Array<string | never> = code.properties.className || []
+
+    const updatedClassName = className.reduce((acc, cls) => {
+      // If cls is something like...
+      // i.e. language-typescript:lib/mdx.ts
+      if (cls.includes(':')) {
+        // Split on the ':'
+        const [langClassName, title] = cls.split(':')
+        // Add the title block to the tree at the index prior
+        // to the <pre /> with the title we found.
+        parent.children.splice(index!, 0, {
+          children: [{ type: 'text', value: title }],
+          properties: { className: ['rehype-code-title'] },
+          tagName: 'div',
+          type: 'element',
+        })
+        acc.push(langClassName)
+        return acc
+      }
+      if (cls.slice(0, 9) === 'language-') {
+        acc.push(cls)
+        return acc
+      }
+      return acc
+    }, [] as Array<string>)
+
+    pre.children = [{ ...code, properties: { className: updatedClassName } }]
+  }
+}
+
+export default rehypeCodeTitles

yarn.lock

@@ -819,6 +819,11 @@
   resolved "https://registry.yarnpkg.com/@types/stack-utils/-/stack-utils-2.0.0.tgz#7036640b4e21cc2f259ae826ce843d277dad8cff"
   integrity sha512-RJJrrySY7A8havqpGObOB4W92QXKJo63/jFLLgpvOtsGUqbQZ9Sbgl35KMm1DjC6j7AvmmU2bIno+3IyEaemaw==
 
+"@types/unist@^2.0.0", "@types/unist@^2.0.3":
+  version "2.0.3"
+  resolved "https://registry.yarnpkg.com/@types/unist/-/unist-2.0.3.tgz#9c088679876f374eb5983f150d4787aa6fb32d7e"
+  integrity sha512-FvUupuM3rlRsRtCN+fDudtmytGO6iHJuuRKS1Ss0pG5z8oX0diNEw94UEL7hgDbpN94rgaK5R7sWm6RrSkZuAQ==
+
 "@types/yargs-parser@*":
   version "20.2.0"
   resolved "https://registry.yarnpkg.com/@types/yargs-parser/-/yargs-parser-20.2.0.tgz#dd3e6699ba3237f0348cd085e4698780204842f9"
@@ -6226,6 +6231,28 @@ union-value@^1.0.0:
     is-extendable "^0.1.1"
     set-value "^2.0.1"
 
+unist-util-is@^5.0.0:
+  version "5.0.0"
+  resolved "https://registry.yarnpkg.com/unist-util-is/-/unist-util-is-5.0.0.tgz#c71eddea34aa7009d54f671a6fafb3779b8035d3"
+  integrity sha512-G4p13DhfdUNmlnJxd0uy5Skx1FG58LSDhX8h1xgpeSq0omOQ4ZN5BO54ToFlNX55NDTbRHMdwTOJXqAieInSEA==
+
+unist-util-visit-parents@^4.0.0:
+  version "4.0.0"
+  resolved "https://registry.yarnpkg.com/unist-util-visit-parents/-/unist-util-visit-parents-4.0.0.tgz#0dfc00046ac753517ffaaf59b80d1ac892b352a6"
+  integrity sha512-QyATSx30wHguIzI82+GVeuXGnFlh3AUVcyeZPOo5Paz2Z52zfRe3/0WLlBv6XlMWcr5xEdFqox6PteUL6hzEFA==
+  dependencies:
+    "@types/unist" "^2.0.0"
+    unist-util-is "^5.0.0"
+
+unist-util-visit@^3.0.0:
+  version "3.0.0"
+  resolved "https://registry.yarnpkg.com/unist-util-visit/-/unist-util-visit-3.0.0.tgz#a8e239038f7b29aadc649a6080f42bc85ea1a7bc"
+  integrity sha512-RbFwAZhMekKPZxlAhUIiBwim8NogwUtwLbIjvZehaGORYRDWcApsnGI1VDUHr/Jo6yW1u8VOqO/djbd7Hpz88A==
+  dependencies:
+    "@types/unist" "^2.0.0"
+    unist-util-is "^5.0.0"
+    unist-util-visit-parents "^4.0.0"
+
 universalify@^0.1.0, universalify@^0.1.2:
   version "0.1.2"
   resolved "https://registry.yarnpkg.com/universalify/-/universalify-0.1.2.tgz#b646f69be3942dabcecc9d6639c80dc105efaa66"