JS-1336 Fix infinite loop in getFullyQualifiedNameTS when import is shadowed (#6402)

Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: zglicz

packages/jsts/src/rules/S2077/unit.test.ts

@@ -257,7 +257,13 @@ describe('S2077', () => {
   it('S2077 with type information', () => {
     const ruleTester = new RuleTester();
     ruleTester.run('Formatting SQL queries is security-sensitive [TS]', rule, {
-      valid: [],
+      valid: [
+        // No infinite loop when local variable shadows imported name
+        {
+          code: `import { geolocation as geo } from "@vercel/functions";
+      const geo = geo(request);`,
+        },
+      ],
       invalid: [
         // mysql: ESM namespace import with concatenation
         {

packages/jsts/src/rules/helpers/ancestor.ts

@@ -17,6 +17,7 @@
 import type { TSESTree } from '@typescript-eslint/utils';
 import { Rule, SourceCode } from 'eslint';
 import type { Node } from 'estree';
+import ts from 'typescript';
 import { functionLike } from './ast.js';
 
 export function findFirstMatchingLocalAncestor(
@@ -99,3 +100,14 @@ export function childrenOf(node: Node, visitorKeys: SourceCode.VisitorKeys): Nod
   }
   return children.filter(Boolean);
 }
+
+export function isTsAncestor(candidate: ts.Node, node: ts.Node): boolean {
+  let current: ts.Node | undefined = node.parent;
+  while (current) {
+    if (current === candidate) {
+      return true;
+    }
+    current = current.parent;
+  }
+  return false;
+}

packages/jsts/src/rules/helpers/module-ts.ts

@@ -16,6 +16,7 @@
  */
 import ts from 'typescript';
 import type { ParserServicesWithTypeInformation } from '@typescript-eslint/utils';
+import { isTsAncestor } from './ancestor.js';
 import { removeNodePrefixIfExists } from './module.js';
 
 export function getFullyQualifiedNameTS(
@@ -104,8 +105,14 @@ export function getFullyQualifiedNameTS(
       case ts.SyntaxKind.Identifier: {
         const identifierSymbol = services.program.getTypeChecker().getSymbolAtLocation(node);
         const declaration = identifierSymbol?.declarations?.at(0);
-        // Handle: no symbol info, compiler module, or self-referential declaration (e.g., `module` in CommonJS)
-        if (isCompilerModule(identifierSymbol) || !declaration || declaration === node) {
+        // Handle: no symbol info, compiler module, self-referential declaration (e.g., `module` in CommonJS),
+        // or declaration that contains the root node (e.g., `const geo = geo(request)` where import is shadowed)
+        if (
+          isCompilerModule(identifierSymbol) ||
+          !declaration ||
+          declaration === node ||
+          isTsAncestor(declaration, rootNode)
+        ) {
           result.push((node as ts.Identifier).text);
           return returnResult();
         } else {