From 5f010c65d8abb8bb4aa6b26ff76ee3fe61563c34 Mon Sep 17 00:00:00 2001
From: fuyou <imshuazi@126.com>
Date: Thu, 31 Jul 2025 12:45:38 +0800
Subject: [PATCH] fix(mock): add support for rejected values in JSMockFunction
 (#21489)

---
 src/bun.js/bindings/JSMockFunction.cpp | 10 ++++++++--
 test/js/bun/test/mock-fn.test.js       |  5 +++++
 2 files changed, 13 insertions(+), 2 deletions(-)

diff --git a/src/bun.js/bindings/JSMockFunction.cpp b/src/bun.js/bindings/JSMockFunction.cpp
index a852d532fe..92f4e15cbd 100644
--- a/src/bun.js/bindings/JSMockFunction.cpp
+++ b/src/bun.js/bindings/JSMockFunction.cpp
@@ -148,6 +148,7 @@ public:
         Call,
         ReturnValue,
         ReturnThis,
+        RejectedValue,
     };
 
     static JSMockImplementation* create(JSC::JSGlobalObject* globalObject, JSC::Structure* structure, Kind kind, JSC::JSValue heldValue, bool isOnce)
@@ -962,6 +963,11 @@ JSC_DEFINE_HOST_FUNCTION(jsMockFunctionCall, (JSGlobalObject * lexicalGlobalObje
             setReturnValue(createMockResult(vm, globalObject, "return"_s, thisValue));
             return JSValue::encode(thisValue);
         }
+        case JSMockImplementation::Kind::RejectedValue: {
+            JSValue rejectedPromise = JSC::JSPromise::rejectedPromise(globalObject, impl->underlyingValue.get());
+            setReturnValue(createMockResult(vm, globalObject, "return"_s, rejectedPromise));
+            return JSValue::encode(rejectedPromise);
+        }
         default: {
             RELEASE_ASSERT_NOT_REACHED();
         }
@@ -1235,7 +1241,7 @@ JSC_DEFINE_HOST_FUNCTION(jsMockFunctionMockRejectedValue, (JSC::JSGlobalObject *
     auto scope = DECLARE_THROW_SCOPE(vm);
     CHECK_IS_MOCK_FUNCTION(thisValue);
 
-    pushImpl(thisObject, globalObject, JSMockImplementation::Kind::ReturnValue, JSC::JSPromise::rejectedPromise(globalObject, callframe->argument(0)));
+    pushImpl(thisObject, globalObject, JSMockImplementation::Kind::RejectedValue, callframe->argument(0));
 
     RELEASE_AND_RETURN(scope, JSValue::encode(thisObject));
 }
@@ -1248,7 +1254,7 @@ JSC_DEFINE_HOST_FUNCTION(jsMockFunctionMockRejectedValueOnce, (JSC::JSGlobalObje
     auto scope = DECLARE_THROW_SCOPE(vm);
     CHECK_IS_MOCK_FUNCTION(thisValue);
 
-    pushImplOnce(thisObject, globalObject, JSMockImplementation::Kind::ReturnValue, JSC::JSPromise::rejectedPromise(globalObject, callframe->argument(0)));
+    pushImplOnce(thisObject, globalObject, JSMockImplementation::Kind::RejectedValue, callframe->argument(0));
 
     RELEASE_AND_RETURN(scope, JSValue::encode(thisObject));
 }
diff --git a/test/js/bun/test/mock-fn.test.js b/test/js/bun/test/mock-fn.test.js
index 4f813f7ffa..6f67cefa1f 100644
--- a/test/js/bun/test/mock-fn.test.js
+++ b/test/js/bun/test/mock-fn.test.js
@@ -599,6 +599,11 @@ describe("mock()", () => {
     expect(await expectRejects(fn())).toBe(44);
     expect(await expectRejects(fn())).toBe(42);
   });
+  test("mockRejectedValue doesn't throw when never called", () => {
+    const fn = jest.fn().mockRejectedValue(new Error("Test error"));
+    expect(fn).toBeDefined();
+    expect(typeof fn).toBe("function");
+  });
   test("withImplementation (sync)", () => {
     const fn = jest.fn(() => "1");
     expect(fn()).toBe("1");