From 2926864a02e1b8fdd06f65a71e65573799d3052f Mon Sep 17 00:00:00 2001
From: robobun <117481402+robobun@users.noreply.github.com>
Date: Wed, 9 Sep 2026 06:52:46 +0000
Subject: [PATCH] ShadowRealm: importValue resolves an export whose value is
 undefined

WEBKIT_VERSION points at the preview build of oven-sh/WebKit#612.

ShadowRealm.prototype.importValue treated an export whose value is
undefined as missing. The ExportGetter checks HasOwnProperty(exports,
name) and then reads the value, so `export const v = undefined` and an
`export let v` that is assigned later now resolve.
---
 scripts/build/deps/webkit.ts   |  2 +-
 test/js/bun/jsc/shadow.test.js | 39 +++++++++++++++++++++++++++++++++-
 2 files changed, 39 insertions(+), 2 deletions(-)

diff --git a/scripts/build/deps/webkit.ts b/scripts/build/deps/webkit.ts
index 7e8ddecce2ac..9de8a2e48df0 100644
--- a/scripts/build/deps/webkit.ts
+++ b/scripts/build/deps/webkit.ts
@@ -3,7 +3,7 @@
  * for local mode. Override via `--webkit-version=<hash>` to test a branch.
  * From https://github.com/oven-sh/WebKit releases.
  */
-export const WEBKIT_VERSION = "2e2aa2290fac856d6f451ceacb58f7f5b44dd057";
+export const WEBKIT_VERSION = "autobuild-preview-pr-612-43d09378";
 
 /**
  * WebKit (JavaScriptCore) — the JS engine.
diff --git a/test/js/bun/jsc/shadow.test.js b/test/js/bun/jsc/shadow.test.js
index 3fdca5391413..248540b6b02e 100644
--- a/test/js/bun/jsc/shadow.test.js
+++ b/test/js/bun/jsc/shadow.test.js
@@ -1,4 +1,6 @@
-import { expect, it } from "bun:test";
+import { describe, expect, it } from "bun:test";
+import { tempDir } from "harness";
+import { join } from "node:path";
 
 it("shadow realm works", () => {
   const red = new ShadowRealm();
@@ -8,3 +10,38 @@ it("shadow realm works", () => {
   expect(globalThis.someValue).toBe(1);
   expect(result).toBe(2);
 });
+
+describe("importValue", () => {
+  // https://tc39.es/proposal-shadowrealm/#sec-export-getter-functions checks HasOwnProperty(exports, name), then reads
+  // the value. An export whose value is undefined exists.
+  it("resolves an export whose value is undefined", async () => {
+    using dir = tempDir("shadow-realm-import-value", {
+      "mod.mjs": `
+        export const undefinedValue = undefined;
+        export let notYet;
+        export function setNotYet(v) { notYet = v; }
+        export const nullValue = null;
+      `,
+    });
+    const mod = join(String(dir), "mod.mjs");
+    const realm = new ShadowRealm();
+    expect(await realm.importValue(mod, "undefinedValue")).toBe(undefined);
+    expect(await realm.importValue(mod, "nullValue")).toBe(null);
+    // A live binding that is still undefined reads its current value each time.
+    expect(await realm.importValue(mod, "notYet")).toBe(undefined);
+    (await realm.importValue(mod, "setNotYet"))("now");
+    expect(await realm.importValue(mod, "notYet")).toBe("now");
+    // A name that is not exported still rejects. That includes names an ordinary object would inherit, and __esModule,
+    // which Bun's module namespace objects inherit from their prototype: the check is HasOwnProperty.
+    for (const name of ["missing", "toString", "__proto__", "constructor", "then", "__esModule"]) {
+      let error;
+      try {
+        await realm.importValue(mod, name);
+      } catch (e) {
+        error = e;
+      }
+      expect(error).toBeInstanceOf(TypeError);
+      expect(error.message).toBe("%ShadowRealm%.importValue requires |exportName| to exist in the |specifier|");
+    }
+  });
+});