Add JSDoc based types

.gitignore

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

index.js

@@ -1,3 +1,12 @@
+/**
+ * @typedef Options
+ *   Configuration.
+ * @property {'github'|'twitter'|RegExp|null|undefined} [style='github']
+ *   Style can be either `'github'` (for GitHub user and team mentions),
+ *   `'twitter'` (for Twitter handles), or a regular expression (such as
+ *   `/^@\w{1,15}$/i`, which is the Twitter regex).
+ */
+
 import {toString} from 'nlcst-to-string'
 import {pointStart, pointEnd} from 'unist-util-position'
 import {visit} from 'unist-util-visit'
@@ -8,8 +17,22 @@ const gh =
   /^@(?:[a-z\d]{1,2}|[a-z\d][a-z\d-]{1,37}[a-z\d])(\/(?:[a-z\d]{1,2}|[a-z\d][a-z\d-]{1,37}[a-z\d]))?$/i
 const tw = /^@\w{1,15}$/i
 
+/**
+ * Plugin to classify @mentions as source, which represents “external
+ * (ungrammatical) values” instead of natural language.
+ * This hides mentions from `retext-spell`, `retext-readability`,
+ * `retext-equality`.
+ *
+ * @type {import('unified').Plugin<[Options?]>}
+ */
 export default function retextSyntaxMentions(options = {}) {
+  /**
+   * @typedef {import('unist').Node<unknown>} Node
+   * @typedef {import('unist').Literal<string>} Literal
+   */
+
   const style = options.style || 'github'
+  /** @type {RegExp} */
   let styleRe
 
   if (style === null || style === undefined || style === 'github') {
@@ -26,12 +49,11 @@ export default function retextSyntaxMentions(options = {}) {
 
   return (tree) => {
     visit(tree, 'SymbolNode', (node, index, parent) => {
-      const siblings = parent.children
-
-      if (toString(node) !== '@') {
+      if (toString(node) !== '@' || !parent || index === null) {
         return
       }
 
+      const siblings = parent.children
       let offset = index + 1
 
       while (offset < siblings.length) {
@@ -53,17 +75,24 @@ export default function retextSyntaxMentions(options = {}) {
         return
       }
 
-      siblings.splice(index, offset - index, {
+      /** @type {Literal} */
+      const replacement = {
         type: 'SourceNode',
         value: toString(slice),
         position: {
           start: pointStart(node),
           end: pointEnd(slice[slice.length - 1])
         }
-      })
+      }
+
+      siblings.splice(index, offset - index, replacement)
     })
   }
 
+  /**
+   * @param {Node[]} nodes
+   * @returns {boolean}
+   */
   function check(nodes) {
     return styleRe.test(toString(nodes).replace(genitive, ''))
   }

package.json

@@ -29,30 +29,38 @@
   "sideEffects": false,
   "type": "module",
   "main": "index.js",
+  "types": "index.d.ts",
   "files": [
+    "index.d.ts",
     "index.js"
   ],
   "dependencies": {
     "nlcst-to-string": "^3.0.0",
+    "unified": "^10.0.0",
     "unist-util-position": "^4.0.0",
     "unist-util-visit": "^3.0.0"
   },
   "devDependencies": {
+    "@types/tape": "^4.0.0",
     "c8": "^7.0.0",
     "prettier": "^2.0.0",
     "remark-cli": "^9.0.0",
     "remark-preset-wooorm": "^8.0.0",
     "retext": "^8.0.0",
+    "rimraf": "^3.0.0",
     "tape": "^5.0.0",
+    "type-coverage": "^2.0.0",
+    "typescript": "^4.0.0",
     "unist-builder": "^3.0.0",
     "unist-util-remove-position": "^4.0.0",
     "xo": "^0.39.0"
   },
   "scripts": {
+    "build": "rimraf \"*.d.ts\" && tsc && type-coverage",
     "format": "remark . -qfo && prettier . -w --loglevel warn && xo --fix",
     "test-api": "node --conditions development test.js",
     "test-coverage": "c8 --check-coverage --branches 100 --functions 100 --lines 100 --statements 100 --reporter lcov node --conditions development test.js",
-    "test": "npm run format && npm run test-coverage"
+    "test": "npm run build && npm run format && npm run test-coverage"
   },
   "prettier": {
     "tabWidth": 2,
@@ -69,5 +77,11 @@
     "plugins": [
       "preset-wooorm"
     ]
+  },
+  "typeCoverage": {
+    "atLeast": 100,
+    "detail": true,
+    "strict": true,
+    "ignoreCatch": true
   }
 }

test.js

@@ -4,19 +4,18 @@ import {u} from 'unist-builder'
 import {removePosition} from 'unist-util-remove-position'
 import retextSyntaxMentions from './index.js'
 
+/** @type {import('unified').Plugin<[]>} */
+const strip = () => (tree) => {
+  removePosition(tree, true)
+}
+
 const position = retext().use(retextSyntaxMentions)
 const noPosition = retext().use(retextSyntaxMentions).use(strip)
 
-function strip() {
-  return transformer
-  function transformer(tree) {
-    removePosition(tree, true)
-  }
-}
-
 test('retext-syntax-mentions', (t) => {
   t.throws(
     () => {
+      // @ts-expect-error: runtime.
       retext().use(retextSyntaxMentions, {style: '!'}).freeze()
     },
     /^Error: Expected known style/,
@@ -275,6 +274,14 @@ test('retext-syntax-mentions', (t) => {
   t.end()
 })
 
+/**
+ * @param {number} l1
+ * @param {number} c1
+ * @param {number} o1
+ * @param {number} l2
+ * @param {number} c2
+ * @param {number} o2
+ */
 // eslint-disable-next-line max-params
 function pos(l1, c1, o1, l2, c2, o2) {
   return {

tsconfig.json

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