From a8cde960ce626c77416edd4b58a8e502bcb0bacc Mon Sep 17 00:00:00 2001
From: Marvin Hagemeister <marvin@deno.com>
Date: Wed, 13 Aug 2025 15:46:51 +0200
Subject: [PATCH] fix(unstable): lint node properties should be enumerable
 (#30391)

This makes npm libraries that traverse the ESTree format like `zimmerframe` or `periscopic` work with our lint ast.
---
 cli/js/40_lint.js              |  3 +++
 tests/unit/lint_plugin_test.ts | 20 +++++++++++++++++++-
 2 files changed, 22 insertions(+), 1 deletion(-)

diff --git a/cli/js/40_lint.js b/cli/js/40_lint.js
index 5d0a10538e..8355c056a5 100644
--- a/cli/js/40_lint.js
+++ b/cli/js/40_lint.js
@@ -607,6 +607,9 @@ function setNodeGetters(ctx) {
     const name = getString(ctx.strTable, id);
 
     Object.defineProperty(FacadeNode.prototype, name, {
+      // The `parent` key is expected to be non-enumerable.
+      // See the npm `zimmerframe` library.
+      enumerable: name !== "parent",
       get() {
         return readValue(
           this[INTERNAL_CTX],
diff --git a/tests/unit/lint_plugin_test.ts b/tests/unit/lint_plugin_test.ts
index 6c1b70719e..30ea116e69 100644
--- a/tests/unit/lint_plugin_test.ts
+++ b/tests/unit/lint_plugin_test.ts
@@ -1,6 +1,6 @@
 // Copyright 2018-2025 the Deno authors. MIT license.
 
-import { assertEquals } from "./test_util.ts";
+import { assert, assertEquals } from "./test_util.ts";
 import { assertSnapshot } from "@std/testing/snapshot";
 
 // TODO(@marvinhagemeister) Remove once we land "official" types
@@ -1228,3 +1228,21 @@ Deno.test("Plugin - TS keywords", async (t) => {
   await testSnapshot(t, "type A = unknown", "TSUnknownKeyword");
   await testSnapshot(t, "type A = void", "TSVoidKeyword");
 });
+
+Deno.test("Plugin - enumerable properties", () => {
+  const keys: string[] = [];
+  testPlugin(`const a = 42`, {
+    create() {
+      return {
+        Program(node) {
+          // deno-lint-ignore guard-for-in
+          for (const k in node) {
+            keys.push(k);
+          }
+        },
+      };
+    },
+  });
+
+  assert(keys.length > 0);
+});