Add type tests

Author: wooorm

index.test-d.ts

@@ -0,0 +1,35 @@
+import {expectType} from 'tsd'
+import type {
+  Delete,
+  Emphasis,
+  Link,
+  LinkReference,
+  Heading,
+  PhrasingContent,
+  Strong,
+  Text
+} from 'mdast'
+import {map} from './index.js'
+
+const text: Text = {type: 'text', value: 'alpha'}
+const heading: Heading = {type: 'heading', depth: 1, children: [text]}
+
+// @ts-expect-error: tree needed.
+map()
+
+// @ts-expect-error: map function needed.
+map(heading)
+
+map(text, function (node) {
+  expectType<Text>(node)
+  return node
+})
+
+map(heading, function (node, index, parent) {
+  expectType<Heading | PhrasingContent>(node)
+  expectType<number | undefined>(index)
+  expectType<
+    Delete | Emphasis | Link | Heading | LinkReference | Strong | undefined
+  >(parent)
+  return node
+})

lib/index.js

@@ -49,9 +49,9 @@
  *   Node type.
  * @typedef {(
  *   (
- *     node: Readonly<InclusiveDescendant<Tree>>,
+ *     node: InclusiveDescendant<Tree>,
  *     index: number | undefined,
- *     parent: Readonly<Extract<InclusiveDescendant<Tree>, UnistParent>> | undefined
+ *     parent: Extract<InclusiveDescendant<Tree>, UnistParent> | undefined
  *   ) => Tree | InclusiveDescendant<Tree>
  * )} MapFunction
  *   Function called with a node, its index, and its parent to produce a new

package.json

@@ -38,19 +38,21 @@
     "@types/unist": "^3.0.0"
   },
   "devDependencies": {
+    "@types/mdast": "^4.0.0",
     "@types/node": "^20.0.0",
     "c8": "^8.0.0",
     "prettier": "^2.0.0",
     "remark-cli": "^11.0.0",
     "remark-preset-wooorm": "^9.0.0",
+    "tsd": "^0.28.0",
     "type-coverage": "^2.0.0",
     "typescript": "^5.0.0",
     "unist-builder": "^4.0.0",
     "xo": "^0.54.0"
   },
   "scripts": {
     "prepack": "npm run build && npm run format",
-    "build": "tsc --build --clean && tsc --build && type-coverage",
+    "build": "tsc --build --clean && tsc --build && tsd && type-coverage",
     "format": "remark . -qfo && prettier . -w --loglevel warn && xo --fix",
     "test-api": "node --conditions development test.js",
     "test-coverage": "c8 --100 --reporter lcov npm run test-api",