fix(eslint-plugin): [prefer-regexp-exec] fix heuristic to check whether regex may contain global flag (typescript-eslint#8764)

kirkwaiblinger · web-flow · commit d951d8321152 · 2024-05-15T17:19:51.000-07:00
* [prefer-regexp-exec] fix heuristic that checks for regexp flags.

* change function name and jsdoc
diff --git a/packages/eslint-plugin/src/rules/prefer-regexp-exec.ts b/packages/eslint-plugin/src/rules/prefer-regexp-exec.ts
@@ -72,22 +72,29 @@ export default createRule({
       return result;
     }
 
-    function isLikelyToContainGlobalFlag(
+    /**
+     * Returns true if and only if we have syntactic proof that the /g flag is
+     * absent. Returns false in all other cases (i.e. it still might or might
+     * not contain the global flag).
+     */
+    function definitelyDoesNotContainGlobalFlag(
       node: TSESTree.CallExpressionArgument,
     ): boolean {
       if (
-        node.type === AST_NODE_TYPES.CallExpression ||
-        node.type === AST_NODE_TYPES.NewExpression
+        (node.type === AST_NODE_TYPES.CallExpression ||
+          node.type === AST_NODE_TYPES.NewExpression) &&
+        node.callee.type === AST_NODE_TYPES.Identifier &&
+        node.callee.name === 'RegExp'
       ) {
         const flags = node.arguments.at(1);
-        return !!(
+        return !(
           flags?.type === AST_NODE_TYPES.Literal &&
           typeof flags.value === 'string' &&
           flags.value.includes('g')
         );
       }
 
-      return node.type === AST_NODE_TYPES.Identifier;
+      return false;
     }
 
     return {
@@ -105,7 +112,8 @@ export default createRule({
 
         // Don't report regular expressions with global flag.
         if (
-          (!argumentValue && isLikelyToContainGlobalFlag(argumentNode)) ||
+          (!argumentValue &&
+            !definitelyDoesNotContainGlobalFlag(argumentNode)) ||
           (argumentValue &&
             argumentValue.value instanceof RegExp &&
             argumentValue.value.flags.includes('g'))
diff --git a/packages/eslint-plugin/tests/rules/prefer-regexp-exec.test.ts b/packages/eslint-plugin/tests/rules/prefer-regexp-exec.test.ts
@@ -82,6 +82,28 @@ function test(str: string) {
   str.match('[a-z');
 }
     `,
+    {
+      code: `
+const text = 'something';
+declare const search: RegExp;
+text.match(search);
+      `,
+    },
+    // https://github.com/typescript-eslint/typescript-eslint/issues/8614
+    {
+      code: `
+const text = 'something';
+declare const obj: { search: RegExp };
+text.match(obj.search);
+      `,
+    },
+    {
+      code: `
+const text = 'something';
+declare function returnsRegexp(): RegExp;
+text.match(returnsRegexp());
+      `,
+    },
   ],
   invalid: [
     {
