Fix to reset lastIndex at false result

lib/index.js

@@ -160,7 +160,12 @@ export function findAndReplace(tree, list, options) {
       }
 
       // It wasn’t a match after all.
-      if (value !== false) {
+      if (value === false) {
+        // False acts as if there was no match.
+        // So we need to reset `lastIndex`, which currently being at the end of
+        // the current match, to the beginning.
+        find.lastIndex = position + 1
+      } else {
         if (start !== position) {
           nodes.push({
             type: 'text',

test.js

@@ -1,3 +1,7 @@
+/**
+ * @typedef {import('mdast').Root} Root
+ */
+
 import assert from 'node:assert/strict'
 import test from 'node:test'
 import {findAndReplace} from 'mdast-util-find-and-replace'
@@ -374,6 +378,30 @@ test('findAndReplace', async function (t) {
     )
   })
 
+  await t.test('should not treat `false` as a match', async function () {
+    /** @type {Root} */
+    const tree = {type: 'root', children: [{type: 'text', value: ':1:2:'}]}
+
+    findAndReplace(tree, [
+      /:(\d+):/g,
+      /**
+       * @param {string} _
+       * @param {string} $1
+       */
+      function (_, $1) {
+        return $1 === '2' ? u('strong', [u('text', $1)]) : false
+      }
+    ])
+
+    assert.deepEqual(tree, {
+      type: 'root',
+      children: [
+        {type: 'text', value: ':1'},
+        {type: 'strong', children: [{type: 'text', value: '2'}]}
+      ]
+    })
+  })
+
   await t.test('should not recurse into a replaced value', async function () {
     const tree = u('paragraph', [u('text', 'asd.')])