From 7200b222c217a7b6354c376c480592fd56fd3c96 Mon Sep 17 00:00:00 2001
From: Rafael Santana <rafaelsantana3095@gmail.com>
Date: Tue, 7 Sep 2021 21:03:28 -0300
Subject: [PATCH] fix(eslint-plugin): [prefer-regexp-exec] respect flags when
 using `RegExp`

---
 .../eslint-plugin/src/rules/prefer-regexp-exec.ts  |  6 +++---
 .../tests/rules/prefer-regexp-exec.test.ts         | 14 +++++++++++++-
 2 files changed, 16 insertions(+), 4 deletions(-)

diff --git a/packages/eslint-plugin/src/rules/prefer-regexp-exec.ts b/packages/eslint-plugin/src/rules/prefer-regexp-exec.ts
index 0d6693715bac..812295ab40c1 100644
--- a/packages/eslint-plugin/src/rules/prefer-regexp-exec.ts
+++ b/packages/eslint-plugin/src/rules/prefer-regexp-exec.ts
@@ -96,9 +96,9 @@ export default createRule({
 
         // Don't report regular expressions with global flag.
         if (
-          argumentValue &&
-          argumentValue.value instanceof RegExp &&
-          argumentValue.value.flags.includes('g')
+          !argumentValue ||
+          (argumentValue.value instanceof RegExp &&
+            argumentValue.value.flags.includes('g'))
         ) {
           return;
         }
diff --git a/packages/eslint-plugin/tests/rules/prefer-regexp-exec.test.ts b/packages/eslint-plugin/tests/rules/prefer-regexp-exec.test.ts
index b45935108071..b35f6d33a2a1 100644
--- a/packages/eslint-plugin/tests/rules/prefer-regexp-exec.test.ts
+++ b/packages/eslint-plugin/tests/rules/prefer-regexp-exec.test.ts
@@ -1,5 +1,5 @@
 import rule from '../../src/rules/prefer-regexp-exec';
-import { RuleTester, getFixturesRootDir } from '../RuleTester';
+import { getFixturesRootDir, RuleTester } from '../RuleTester';
 
 const rootPath = getFixturesRootDir();
 
@@ -56,6 +56,18 @@ const matchers = [{ match: (s: RegExp) => false }];
 const file = '';
 matchers.some(matcher => !!file.match(matcher));
     `,
+    // https://github.com/typescript-eslint/typescript-eslint/issues/3477
+    `
+function test(pattern: string) {
+  'hello hello'.match(RegExp(pattern, 'g'))?.reduce(() => []);
+}
+    `,
+    // https://github.com/typescript-eslint/typescript-eslint/issues/3477
+    `
+function test(pattern: string) {
+  'hello hello'.match(new RegExp(pattern, 'gi'))?.reduce(() => []);
+}
+    `,
   ],
   invalid: [
     {