From 9e7f25ab878c0fc40ddc1c53a76c7a1c62768e99 Mon Sep 17 00:00:00 2001
From: Tim Deschryver <28659384+timdeschryver@users.noreply.github.com>
Date: Tue, 22 Mar 2022 19:26:38 +0100
Subject: [PATCH] fix: prevent state on regexp with global flag

---
 src/__tests__/matches.js | 16 ++++++++++++++++
 src/matches.ts           | 15 +++++++++++++--
 2 files changed, 29 insertions(+), 2 deletions(-)

diff --git a/src/__tests__/matches.js b/src/__tests__/matches.js
index 3d512e65..629c283b 100644
--- a/src/__tests__/matches.js
+++ b/src/__tests__/matches.js
@@ -15,6 +15,22 @@ test('matchers accept regex', () => {
   expect(fuzzyMatches('ABC', node, /ABC/, normalizer)).toBe(true)
 })
 
+// https://stackoverflow.com/questions/1520800/why-does-a-regexp-with-global-flag-give-wrong-results
+test('a regex with the global flag consistently (re-)finds a match', () => {
+  const regex = /ABC/g
+  const spy = jest.spyOn(console, 'warn').mockImplementation()
+
+  expect(matches('ABC', node, regex, normalizer)).toBe(true)
+  expect(fuzzyMatches('ABC', node, regex, normalizer)).toBe(true)
+
+  expect(spy).toBeCalledTimes(2)
+  expect(spy).toHaveBeenCalledWith(
+    `To match all elements we had to reset the lastIndex of the RegExp because the global flag is enabled. We encourage to remove the global flag from the RegExp.`,
+  )
+
+  console.warn.mockClear()
+})
+
 test('matchers accept functions', () => {
   expect(matches('ABC', node, text => text === 'ABC', normalizer)).toBe(true)
   expect(fuzzyMatches('ABC', node, text => text === 'ABC', normalizer)).toBe(
diff --git a/src/matches.ts b/src/matches.ts
index 31670d1d..c49c7cca 100644
--- a/src/matches.ts
+++ b/src/matches.ts
@@ -36,7 +36,7 @@ function fuzzyMatches(
   } else if (typeof matcher === 'function') {
     return matcher(normalizedText, node)
   } else {
-    return matcher.test(normalizedText)
+    return matchRegExp(matcher, normalizedText)
   }
 }
 
@@ -56,7 +56,7 @@ function matches(
   if (matcher instanceof Function) {
     return matcher(normalizedText, node)
   } else if (matcher instanceof RegExp) {
-    return matcher.test(normalizedText)
+    return matchRegExp(matcher, normalizedText)
   } else {
     return normalizedText === String(matcher)
   }
@@ -111,4 +111,15 @@ function makeNormalizer({
   return normalizer
 }
 
+function matchRegExp(matcher: RegExp, text: string) {
+  const match = matcher.test(text)
+  if (matcher.global && matcher.lastIndex !== 0) {
+    console.warn(
+      `To match all elements we had to reset the lastIndex of the RegExp because the global flag is enabled. We encourage to remove the global flag from the RegExp.`,
+    )
+    matcher.lastIndex = 0
+  }
+  return match
+}
+
 export {fuzzyMatches, matches, getDefaultNormalizer, makeNormalizer}