Add JSDoc based types

.gitignore

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

index.js

@@ -1,17 +1,34 @@
+/**
+ * @typedef {import('mdast').Root} Root
+ * @typedef {import('micromark-extension-gfm').Options & import('mdast-util-gfm').Options} Options
+ */
+
 import {gfm} from 'micromark-extension-gfm'
 import {gfmFromMarkdown, gfmToMarkdown} from 'mdast-util-gfm'
 
-export default function remarkGfm(options) {
+/**
+ * Plugin to support GitHub Flavored Markdown (GFM).
+ *
+ * @type {import('unified').Plugin<[Options?]|void[], Root>}
+ */
+export default function remarkGfm(options = {}) {
   const data = this.data()
 
   add('micromarkExtensions', gfm(options))
   add('fromMarkdownExtensions', gfmFromMarkdown)
   add('toMarkdownExtensions', gfmToMarkdown(options))
 
+  /**
+   * @param {string} field
+   * @param {unknown} value
+   */
   function add(field, value) {
-    // Other extensions.
-    /* c8 ignore next */
-    if (data[field]) data[field].push(value)
-    else data[field] = [value]
+    const list = /** @type {unknown[]} */ (
+      // Other extensions
+      /* c8 ignore next 2 */
+      data[field] ? data[field] : (data[field] = [])
+    )
+
+    list.push(value)
   }
 }

package.json

@@ -30,33 +30,40 @@
   "sideEffects": false,
   "type": "module",
   "main": "index.js",
+  "types": "index.d.ts",
   "files": [
+    "index.d.ts",
     "index.js"
   ],
   "dependencies": {
+    "@types/mdast": "^3.0.0",
     "mdast-util-gfm": "^1.0.0",
-    "micromark-extension-gfm": "^1.0.0"
+    "micromark-extension-gfm": "^1.0.0",
+    "unified": "^10.0.0"
   },
   "devDependencies": {
+    "@types/tape": "^4.0.0",
     "c8": "^7.0.0",
     "dtslint": "^4.0.0",
     "is-hidden": "^2.0.0",
     "prettier": "^2.0.0",
     "remark": "^14.0.0",
     "remark-cli": "^10.0.0",
     "remark-preset-wooorm": "^8.0.0",
+    "rimraf": "^3.0.0",
     "string-width": "^5.0.0",
     "tape": "^5.0.0",
     "to-vfile": "^7.0.0",
-    "unified": "^10.0.0",
+    "type-coverage": "^2.0.0",
+    "typescript": "^4.0.0",
     "xo": "^0.39.0"
   },
   "scripts": {
+    "build": "rimraf \"test/**/*.d.ts\" \"*.d.ts\" && tsc && type-coverage",
     "format": "remark . -qfo --ignore-pattern test/ && 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-types": "dtslint types",
-    "test": "npm run format && npm run test-coverage && npm run test-types"
+    "test": "npm run build && npm run format && npm run test-coverage"
   },
   "prettier": {
     "tabWidth": 2,
@@ -67,14 +74,17 @@
     "trailingComma": "none"
   },
   "xo": {
-    "prettier": true,
-    "ignore": [
-      "types/"
-    ]
+    "prettier": true
   },
   "remarkConfig": {
     "plugins": [
       "preset-wooorm"
     ]
+  },
+  "typeCoverage": {
+    "atLeast": 100,
+    "detail": true,
+    "strict": true,
+    "ignoreCatch": true
   }
 }

test/index.js

@@ -1,3 +1,8 @@
+/**
+ * @typedef {import('mdast').Root} Root
+ * @typedef {import('../index.js').Options} Options
+ */
+
 import fs from 'fs'
 import path from 'path'
 import test from 'tape'
@@ -31,32 +36,33 @@ test('fixtures', (t) => {
     const file = readSync(path.join(base, entries[index], 'input.md'))
     const input = String(file.value)
     const treePath = path.join(base, entries[index], 'tree.json')
+    /** @type {Options|undefined} */
     let config
 
     try {
       config = JSON.parse(
-        fs.readFileSync(path.join(base, entries[index], 'config.json'))
+        String(fs.readFileSync(path.join(base, entries[index], 'config.json')))
       )
-    } catch {
-      config = undefined
-    }
+    } catch {}
 
     if (entries[index] === 'table-string-length') {
       config = {stringLength: stringWidth}
     }
 
     const proc = remark().use(gfm, config).freeze()
     const actual = proc.parse(file)
+    /** @type {Root} */
     let expected
 
     try {
-      expected = JSON.parse(fs.readFileSync(treePath))
+      expected = JSON.parse(String(fs.readFileSync(treePath)))
     } catch {
       // New fixture.
-      fs.writeFileSync(treePath, JSON.stringify(actual, 0, 2) + '\n')
+      fs.writeFileSync(treePath, JSON.stringify(actual, null, 2) + '\n')
       expected = actual
     }
 
+    /** @type {string} */
     let output
 
     try {

tsconfig.json

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