From d5c8615c3c10e07123fe7edb229a11c683290941 Mon Sep 17 00:00:00 2001
From: "copilot-swe-agent[bot]" <198982749+Copilot@users.noreply.github.com>
Date: Sun, 5 Jul 2026 07:25:30 +0000
Subject: [PATCH 1/3] Initial plan


From 69d37b5ef4c717628f3a4542ef3488686bc25cff Mon Sep 17 00:00:00 2001
From: "copilot-swe-agent[bot]" <198982749+Copilot@users.noreply.github.com>
Date: Sun, 5 Jul 2026 07:44:08 +0000
Subject: [PATCH 2/3] fix(eslint-factory): treat import bindings as local
 shadows in prefer-number-isnan

Co-authored-by: pelikhan <4175913+pelikhan@users.noreply.github.com>
---
 eslint-factory/src/rules/prefer-number-isnan.test.ts | 3 +++
 eslint-factory/src/rules/prefer-number-isnan.ts      | 3 ++-
 2 files changed, 5 insertions(+), 1 deletion(-)

diff --git a/eslint-factory/src/rules/prefer-number-isnan.test.ts b/eslint-factory/src/rules/prefer-number-isnan.test.ts
index 080aef770fe..269f10d03f2 100644
--- a/eslint-factory/src/rules/prefer-number-isnan.test.ts
+++ b/eslint-factory/src/rules/prefer-number-isnan.test.ts
@@ -34,9 +34,12 @@ describe("prefer-number-isnan", () => {
       valid: [
         `function isNaN(value) { return false; } isNaN(value);`,
         `const isNaN = Number.isNaN; isNaN(value);`,
+        `import { isNaN } from "lodash"; isNaN(value);`,
         `const globalThis = { isNaN(value) { return value; } }; globalThis.isNaN(value);`,
         `const window = { isNaN(value) { return value; } }; window["isNaN"](value);`,
         `const global = { isNaN(value) { return value; } }; global.isNaN(value);`,
+        `import { window } from "./browser-shim"; window.isNaN(value);`,
+        `import { global } from "./server-shim"; global["isNaN"](value);`,
         // Dynamic computed access — identifier property reference, not string literal "isNaN"
         `globalThis[isNaN](value);`,
       ],
diff --git a/eslint-factory/src/rules/prefer-number-isnan.ts b/eslint-factory/src/rules/prefer-number-isnan.ts
index d6e55111379..0589239b1d1 100644
--- a/eslint-factory/src/rules/prefer-number-isnan.ts
+++ b/eslint-factory/src/rules/prefer-number-isnan.ts
@@ -34,7 +34,8 @@ export const preferNumberIsNanRule = createRule({
       while (scope) {
         const variable = scope.set.get(name);
 
-        if (variable?.defs.some(d => d.type !== "ImportBinding")) {
+        // Any local definition shadows the global (including ESM ImportBinding).
+        if (variable && variable.defs.length > 0) {
           return true;
         }
 

From 1e59acdc5ed9713a748206ce4953cb17fab3955b Mon Sep 17 00:00:00 2001
From: "copilot-swe-agent[bot]" <198982749+Copilot@users.noreply.github.com>
Date: Sun, 5 Jul 2026 09:42:58 +0000
Subject: [PATCH 3/3] test(eslint-factory): add globalThis ESM import-shadow
 case and ESM invalid tests

Co-authored-by: gh-aw-bot <259018956+gh-aw-bot@users.noreply.github.com>
---
 .../src/rules/prefer-number-isnan.test.ts       | 17 +++++++++++++++++
 1 file changed, 17 insertions(+)

diff --git a/eslint-factory/src/rules/prefer-number-isnan.test.ts b/eslint-factory/src/rules/prefer-number-isnan.test.ts
index 269f10d03f2..e27bbb0fbde 100644
--- a/eslint-factory/src/rules/prefer-number-isnan.test.ts
+++ b/eslint-factory/src/rules/prefer-number-isnan.test.ts
@@ -38,6 +38,7 @@ describe("prefer-number-isnan", () => {
         `const globalThis = { isNaN(value) { return value; } }; globalThis.isNaN(value);`,
         `const window = { isNaN(value) { return value; } }; window["isNaN"](value);`,
         `const global = { isNaN(value) { return value; } }; global.isNaN(value);`,
+        `import { globalThis } from "./global-shim"; globalThis.isNaN(value);`,
         `import { window } from "./browser-shim"; window.isNaN(value);`,
         `import { global } from "./server-shim"; global["isNaN"](value);`,
         // Dynamic computed access — identifier property reference, not string literal "isNaN"
@@ -102,4 +103,20 @@ describe("prefer-number-isnan", () => {
       ],
     });
   });
+
+  it("invalid: global isNaN() is still flagged in ESM mode without a shadow", () => {
+    esmRuleTester.run("prefer-number-isnan", preferNumberIsNanRule, {
+      valid: [],
+      invalid: [
+        {
+          code: `isNaN(value);`,
+          errors: [{ messageId: "preferNumberIsNaN", suggestions: [{ messageId: "replaceWithNumberIsNaN", output: `Number.isNaN(value);` }] }],
+        },
+        {
+          code: `window.isNaN(value);`,
+          errors: [{ messageId: "preferNumberIsNaN", suggestions: [{ messageId: "replaceWithNumberIsNaN", output: `Number.isNaN(value);` }] }],
+        },
+      ],
+    });
+  });
 });