Add strict to tsconfig.json

Author: wooorm

index.js

@@ -9,10 +9,11 @@
  * @property {Parent|null} parent
  *
  * @callback Handler
- * @param {Node|undefined} start
+ * @param {Node} start
  * @param {Array.<Node>} between
- * @param {Node|undefined} end
+ * @param {Node} end
  * @param {ZoneInfo} info
+ * @returns {Array.<Node>|null|undefined|void}
  */
 
 import {commentMarker} from 'mdast-comment-marker'
@@ -24,11 +25,11 @@ import {visit} from 'unist-util-visit'
  * @param {Handler} callback
  */
 export function zone(node, name, callback) {
-  /** @type {number} */
+  /** @type {number|undefined} */
   let level
-  /** @type {Node} */
+  /** @type {Node|undefined} */
   let marker
-  /** @type {Parent} */
+  /** @type {Parent|undefined} */
   let scope
 
   visit(node, gather)
@@ -43,14 +44,14 @@ export function zone(node, name, callback) {
       info && info.name === name && info.attributes.match(/(start|end)\b/)
     const type = match && match[0]
 
-    if (type) {
+    if (parent && index !== null && type) {
       if (!scope && type === 'start') {
         level = 0
         marker = node
         scope = parent
       }
 
-      if (scope && parent === scope) {
+      if (typeof level === 'number' && marker && scope && parent === scope) {
         if (type === 'start') {
           level++
         } else {

test/fixtures/replace-children/index.js

@@ -10,11 +10,11 @@ export default function assertion(_, zone, tree) {
   function handle(start, _, end) {
     return [
       start,
-      {
+      /** @type {import('mdast').Heading} */ ({
         type: 'heading',
         depth: 2,
         children: [{type: 'text', value: 'Bar'}]
-      },
+      }),
       end
     ]
   }

test/index.js

@@ -15,16 +15,11 @@ test('mdast-zone', async (t) => {
   const root = path.join('test', 'fixtures')
   const fixtures = fs.readdirSync(root)
   let index = -1
-  /** @type {string} */
-  let output
-  /** @type {string} */
-  let name
-  /** @type {(t: Test, zone: Zone, node: Node) => void} */
-  let mod
 
   while (++index < fixtures.length) {
-    name = fixtures[index]
-    output = null
+    const name = fixtures[index]
+    /** @type {string|undefined} */
+    let output
 
     if (isHidden(name)) continue
 
@@ -33,7 +28,8 @@ test('mdast-zone', async (t) => {
     } catch {}
 
     /* eslint-disable no-await-in-loop */
-    mod =
+    /** @type {(t: Test, zone: Zone, node: Node) => void} */
+    const mod =
       // @ts-ignore hush.
       (await import(new URL('fixtures/' + name + '/index.js', import.meta.url)))
         .default // type-coverage:ignore-line

tsconfig.json

@@ -10,6 +10,7 @@
     "declaration": true,
     "emitDeclarationOnly": true,
     "allowSyntheticDefaultImports": true,
-    "skipLibCheck": true
+    "skipLibCheck": true,
+    "strict": true
   }
 }