Add JSDoc based types

.gitignore

@@ -1,5 +1,6 @@
 coverage/
 node_modules/
 .DS_Store
+*.d.ts
 *.log
 yarn.lock

index.js

@@ -1,94 +1,158 @@
+/**
+ * @typedef {import('hast').Root} Root
+ * @typedef {import('hast').Parent} Parent
+ * @typedef {import('hast').Element} Element
+ * @typedef {Element['children'][number]} ElementChild
+ * @typedef {import('hast').Properties} Properties
+ *
+ * @typedef {'prepend'|'append'|'wrap'|'before'|'after'} Behavior
+ *
+ * @callback Build
+ * @param {Element} node
+ * @returns {ElementChild|ElementChild[]}
+ *
+ * @typedef Options
+ *   Configuration.
+ * @property {Behavior} [behavior='prepend']
+ *   How to create links.
+ * @property {Behavior} [behaviour]
+ *   Please use `behavior` instead
+ * @property {Properties} [properties]
+ *   Extra properties to set on the link when injecting.
+ *   Defaults to `{ariaHidden: true, tabIndex: -1}` when `'prepend'` or
+ *   `'append'`.
+ * @property {ElementChild|ElementChild[]|Build} [content={type: 'element', tagName: 'span', properties: {className: ['icon', 'icon-link']}, children: []}]
+ *   hast nodes to insert in the link.
+ * @property {ElementChild|ElementChild[]|Build} [group]
+ *   hast node to wrap the heading and link with, if `behavior` is `'before'` or
+ *   `'after'`.
+ *   There is no default.
+ */
+
 import extend from 'extend'
 import {hasProperty} from 'hast-util-has-property'
 import {headingRank} from 'hast-util-heading-rank'
-import {visit} from 'unist-util-visit'
+import {visit, SKIP} from 'unist-util-visit'
 
+/** @type {Element} */
 const contentDefaults = {
   type: 'element',
   tagName: 'span',
   properties: {className: ['icon', 'icon-link']},
   children: []
 }
 
+/**
+ * Plugin to automatically add links to headings (h1-h6).
+ *
+ * @type {import('unified').Plugin<[Options?]|void[], Root>}
+ */
 export default function rehypeAutolinkHeadings(options = {}) {
   let props = options.properties
   const behavior = options.behaviour || options.behavior || 'prepend'
   const content = options.content || contentDefaults
   const group = options.group
+
+  /** @type {import('unist-util-visit').Visitor<Element>} */
   let method
 
   if (behavior === 'wrap') {
     method = wrap
   } else if (behavior === 'before' || behavior === 'after') {
     method = around
   } else {
-    method = inject
-
     if (!props) {
       props = {ariaHidden: 'true', tabIndex: -1}
     }
-  }
-
-  return transformer
 
-  function transformer(tree) {
-    visit(tree, 'element', visitor)
+    method = inject
   }
 
-  function visitor(node, index, parent) {
-    if (headingRank(node) && hasProperty(node, 'id')) {
-      return method(node, index, parent)
-    }
+  return (tree) => {
+    visit(tree, 'element', (node, index, parent) => {
+      if (headingRank(node) && hasProperty(node, 'id')) {
+        return method(node, index, parent)
+      }
+    })
   }
 
+  /** @type {import('unist-util-visit').Visitor<Element>} */
   function inject(node) {
     node.children[behavior === 'prepend' ? 'unshift' : 'push'](
       create(node, extend(true, {}, props), toChildren(content, node))
     )
 
-    return [visit.SKIP]
+    return [SKIP]
   }
 
+  /** @type {import('unist-util-visit').Visitor<Element>} */
   function around(node, index, parent) {
+    // Uncommon.
+    /* c8 ignore next */
+    if (typeof index !== 'number' || !parent) return
+
     const link = create(
       node,
       extend(true, {}, props),
       toChildren(content, node)
     )
     let nodes = behavior === 'before' ? [link, node] : [node, link]
-    const grouping = group && toNode(group, node)
 
-    if (grouping) {
-      grouping.children = nodes
-      nodes = [grouping]
+    if (group) {
+      const grouping = toNode(group, node)
+
+      if (grouping && !Array.isArray(grouping) && grouping.type === 'element') {
+        grouping.children = nodes
+        nodes = [grouping]
+      }
     }
 
     parent.children.splice(index, 1, ...nodes)
 
-    return [visit.SKIP, index + nodes.length]
+    return [SKIP, index + nodes.length]
   }
 
+  /** @type {import('unist-util-visit').Visitor<Element>} */
   function wrap(node) {
     node.children = [create(node, extend(true, {}, props), node.children)]
-
-    return [visit.SKIP]
+    return [SKIP]
   }
 
+  /**
+   * @param {ElementChild|ElementChild[]|Build} value
+   * @param {Element} node
+   * @returns {ElementChild[]}
+   */
   function toChildren(value, node) {
     const result = toNode(value, node)
     return Array.isArray(result) ? result : [result]
   }
 
+  /**
+   * @param {ElementChild|ElementChild[]|Build} value
+   * @param {Element} node
+   * @returns {ElementChild|ElementChild[]}
+   */
   function toNode(value, node) {
     if (typeof value === 'function') return value(node)
     return extend(true, Array.isArray(value) ? [] : {}, value)
   }
 
+  /**
+   * @param {Element} node
+   * @param {Properties} props
+   * @param {ElementChild[]} children
+   * @returns {Element}
+   */
   function create(node, props, children) {
     return {
       type: 'element',
       tagName: 'a',
-      properties: Object.assign({}, props, {href: '#' + node.properties.id}),
+      properties: Object.assign({}, props, {
+        // Fix hast types and make them required.
+        /* c8 ignore next */
+        href: '#' + (node.properties || {}).id
+      }),
       children
     }
   }

package.json

@@ -25,34 +25,42 @@
   "sideEffects": false,
   "type": "module",
   "main": "index.js",
+  "types": "index.d.ts",
   "files": [
+    "index.d.ts",
     "index.js"
   ],
   "dependencies": {
+    "@types/hast": "^2.0.0",
     "extend": "^3.0.0",
     "hast-util-has-property": "^2.0.0",
     "hast-util-heading-rank": "^2.0.0",
+    "unified": "^10.0.0",
     "unist-util-visit": "^4.0.0"
   },
   "devDependencies": {
-    "@types/hast": "^2.0.0",
+    "@types/extend": "^3.0.1",
+    "@types/tape": "^4.0.0",
     "bail": "^2.0.0",
     "c8": "^7.0.0",
     "is-hidden": "^2.0.0",
     "prettier": "^2.0.0",
     "rehype": "^12.0.0",
     "remark-cli": "^9.0.0",
     "remark-preset-wooorm": "^8.0.0",
+    "rimraf": "^3.0.0",
     "tape": "^5.0.0",
     "to-vfile": "^7.0.0",
-    "unified": "^10.0.0",
+    "type-coverage": "^2.0.0",
+    "typescript": "^4.0.0",
     "xo": "^0.38.0"
   },
   "scripts": {
+    "build": "rimraf \"*.d.ts\" \"test/**/*.d.ts\" && tsc && type-coverage",
     "format": "remark . -qfo && prettier . -w --loglevel warn && xo --fix",
     "test-api": "node --conditions development test/index.js",
     "test-coverage": "c8 --check-coverage --branches 100 --functions 100 --lines 100 --statements 100 --reporter lcov npm run test-api",
-    "test": "npm run format && npm run test-coverage"
+    "test": "npm run build && npm run format && npm run test-coverage"
   },
   "prettier": {
     "tabWidth": 2,
@@ -72,5 +80,11 @@
     "plugins": [
       "preset-wooorm"
     ]
+  },
+  "typeCoverage": {
+    "atLeast": 100,
+    "detail": true,
+    "strict": true,
+    "ignoreCatch": true
   }
 }

test/index.js

@@ -1,3 +1,7 @@
+/**
+ * @typedef {import('../index.js').Options} Options
+ */
+
 import fs from 'fs'
 import path from 'path'
 import {bail} from 'bail'
@@ -13,25 +17,32 @@ test('rehypeAutolinkHeadings', (t) => {
   t.test('fixtures', (t) => {
     fs.readdir(root, (error, files) => {
       bail(error)
-      files = files.filter((d) => !isHidden(d))
 
-      t.plan(files.length)
+      const visible = files.filter((d) => !isHidden(d))
+
+      t.plan(visible.length)
 
       let index = -1
 
-      while (++index < files.length) {
-        one(files[index])
+      while (++index < visible.length) {
+        one(visible[index])
       }
     })
 
+    /**
+     * @param {string} fixture
+     */
     function one(fixture) {
       const base = path.join(root, fixture)
       const input = readSync(path.join(base, 'input.html'))
       const output = readSync(path.join(base, 'output.html'))
+      /** @type {Options|undefined} */
       let config
 
       try {
-        config = JSON.parse(fs.readFileSync(path.join(base, 'config.json')))
+        config = JSON.parse(
+          String(fs.readFileSync(path.join(base, 'config.json')))
+        )
       } catch {}
 
       t.test(fixture, (t) => {
@@ -56,17 +67,25 @@ test('rehypeAutolinkHeadings', (t) => {
       .use(rehypeAutolinkHeadings, {
         behavior: 'after',
         group: (node) => {
-          t.equal(node.properties.id, 'a', 'should pass `node` to `group`')
+          t.equal(
+            node.properties && node.properties.id,
+            'a',
+            'should pass `node` to `group`'
+          )
           return {type: 'element', tagName: 'div', properties: {}, children: []}
         },
         content: (node) => {
-          t.equal(node.properties.id, 'a', 'should pass `node` to `content`')
+          t.equal(
+            node.properties && node.properties.id,
+            'a',
+            'should pass `node` to `content`'
+          )
           return {type: 'element', tagName: 'i', properties: {}, children: []}
         }
       })
       .process('<h1 id=a>b</h1>', (error, file) => {
         t.deepEqual(
-          [error, file.messages.length, String(file)],
+          [error, (file || {messages: []}).messages.length, String(file)],
           [null, 0, '<div><h1 id="a">b</h1><a href="#a"><i></i></a></div>']
         )
       })

tsconfig.json

@@ -0,0 +1,16 @@
+{
+  "include": ["*.js", "test/**/*.js"],
+  "compilerOptions": {
+    "target": "ES2020",
+    "lib": ["ES2020"],
+    "module": "ES2020",
+    "moduleResolution": "node",
+    "allowJs": true,
+    "checkJs": true,
+    "declaration": true,
+    "emitDeclarationOnly": true,
+    "allowSyntheticDefaultImports": true,
+    "skipLibCheck": true,
+    "strict": true
+  }
+}