Add support for a content function

Related to GH-49.

readme.md

@@ -45,7 +45,7 @@ const html = require('remark-html')
 const slug = require('remark-slug')
 const headings = require('remark-autolink-headings')
 
-const contents = unified()
+const doc = unified()
   .use(markdown)
   .use(slug)
   // Note that this module must be included after `remark-slug`.
@@ -54,7 +54,7 @@ const contents = unified()
   .processSync(fs.readFileSync('example.md'))
   .toString()
 
-console.log(contents)
+console.log(doc)
 ```
 
 Now, running `node example` yields:
@@ -86,7 +86,7 @@ option.
 
 ###### `options.content`
 
-[**hast**][hast] nodes to insert in the link (`Node|Children`).
+[**hast**][hast] nodes to insert in the link (`Function|Node|Children`).
 By default, the following is used:
 
 ```js
@@ -97,6 +97,23 @@ By default, the following is used:
 }
 ```
 
+If `content` is a function, it’s called with the current heading (`Node`) and
+should return one or more nodes:
+
+```js
+const toString = require('mdast-util-to-string')
+const h = require('hastscript')
+
+// …
+
+function content(node) {
+  return [
+    h('span.visually-hidden', 'Read the “', toString(node), '” section'),
+    h('span.icon.icon-link', {ariaHidden: true})
+  ]
+}
+```
+
 ###### `options.linkProperties`
 
 Extra properties to set on the link (`Object?`).

src/__tests__/index.js

@@ -63,6 +63,25 @@ test('should accept custom content as an array', (t) => {
   )
 })
 
+test('should accept custom content as a function', (t) => {
+  t.is(
+    remark()
+      .use(slug)
+      .use(html)
+      .use(headings, {content, linkProperties: {}})
+      .processSync('# method')
+      .toString(),
+    '<h1 id="method"><a href="#method">Read the “method” section</a>method</h1>\n'
+  )
+
+  function content(node) {
+    return {
+      type: 'text',
+      value: 'Read the “' + node.children[0].value + '” section'
+    }
+  }
+})
+
 test('should accept link properties', (t) => {
   t.is(
     remark()

src/index.js

@@ -16,7 +16,6 @@ let deprecationWarningIssued = false
 export default function attacher(options = {}) {
   let {linkProperties, behavior, content} = {...defaults, ...options}
   let method
-  let hChildren
 
   // NOTE: Remove in next major version
   if (options.behaviour !== undefined) {
@@ -34,7 +33,6 @@ export default function attacher(options = {}) {
     method = wrap
   } else {
     method = inject
-    hChildren = Array.isArray(content) ? content : [content]
 
     if (!linkProperties) {
       linkProperties = {ariaHidden: 'true', tabIndex: -1}
@@ -53,15 +51,21 @@ export default function attacher(options = {}) {
   }
 
   function inject(node, url) {
+    const hProperties = extend(true, {}, linkProperties)
+    let hChildren = typeof content === 'function' ? content(node) : content
+
+    hChildren = Array.isArray(hChildren) ? hChildren : [hChildren]
+
+    if (typeof content !== 'function') {
+      hChildren = extend(true, [], hChildren)
+    }
+
     node.children[behaviors[behavior]]({
       type: 'link',
       url,
       title: null,
       children: [],
-      data: {
-        hProperties: extend(true, {}, linkProperties),
-        hChildren: extend(true, [], hChildren)
-      }
+      data: {hProperties, hChildren}
     })
   }