fix: add stack trace to AbortSignal.timeout errorsfix: add stack trace to AbortSignal.timeout errors

src/bun.js/bindings/ErrorCode.cpp

@@ -1642,11 +1642,25 @@ JSC_DEFINE_HOST_FUNCTION(jsFunctionMakeAbortError, (JSC::JSGlobalObject * lexica
     return JSC::JSValue::encode(error);
 }
 
-JSC::JSValue WebCore::toJS(JSC::JSGlobalObject* globalObject, CommonAbortReason abortReason)
+JSC::JSValue WebCore::toJS(JSC::JSGlobalObject* globalObject, CommonAbortReason abortReason, JSC::JSObject* capturedStack)
 {
+    auto& vm = globalObject->vm();
     switch (abortReason) {
     case CommonAbortReason::Timeout: {
-        return createDOMException(globalObject, ExceptionCode::TimeoutError, "The operation timed out."_s);
+        auto error = createDOMException(globalObject, ExceptionCode::TimeoutError, "The operation timed out."_s);
+
+        // If we have a captured stack (from AbortSignal.timeout() call site), copy it to this error
+        if (capturedStack) {
+            auto scope = DECLARE_CATCH_SCOPE(vm);
+            JSValue stackValue = capturedStack->get(globalObject, vm.propertyNames->stack);
+            if (!scope.exception() && stackValue && !stackValue.isUndefined()) {
+                if (auto* errorObject = error.getObject()) {
+                    errorObject->putDirect(vm, vm.propertyNames->stack, stackValue, 0);
+                }
+            }
+            scope.clearException();
+        }
+        return error;
     }
     case CommonAbortReason::UserAbort: {
         return createDOMException(globalObject, ExceptionCode::AbortError, "The operation was aborted."_s);
@@ -1664,7 +1678,7 @@ JSC::JSValue WebCore::toJS(JSC::JSGlobalObject* globalObject, CommonAbortReason
 
 extern "C" JSC::EncodedJSValue WebCore__CommonAbortReason__toJS(JSC::JSGlobalObject* globalObject, WebCore::CommonAbortReason abortReason)
 {
-    return JSC::JSValue::encode(WebCore::toJS(globalObject, abortReason));
+    return JSC::JSValue::encode(WebCore::toJS(globalObject, abortReason, nullptr));
 }
 
 JSC::JSObject* Bun::createInvalidThisError(JSC::JSGlobalObject* globalObject, const String& message)

src/bun.js/bindings/webcore/AbortSignal.cpp

@@ -66,6 +66,18 @@ Ref<AbortSignal> AbortSignal::abort(JSDOMGlobalObject& globalObject, ScriptExecu
 Ref<AbortSignal> AbortSignal::timeout(ScriptExecutionContext& context, uint64_t milliseconds)
 {
     auto signal = adoptRef(*new AbortSignal(&context));
+
+    // Capture stack trace at creation time for later use when timeout fires
+    // This ensures the TimeoutError has a stack trace pointing to where timeout() was called
+    if (auto* globalObject = context.jsGlobalObject()) {
+        auto& vm = globalObject->vm();
+        JSC::JSObject* errorForStack = JSC::constructEmptyObject(globalObject);
+        if (auto* errorInstance = JSC::jsDynamicCast<JSC::ErrorInstance*>(JSC::createError(globalObject, String()))) {
+            errorInstance->captureStackTrace(vm, globalObject, 1);
+            signal->m_timeoutCreationStack.setWeakly(errorInstance);
+        }
+    }
+
     signal->m_timeout = AbortSignal__Timeout__create(bunVM(context.vm()), signal.ptr(), milliseconds);
     ASSERT(signal->m_timeout);
     signal->ref();
@@ -210,7 +222,10 @@ void AbortSignal::signalAbort(JSC::JSGlobalObject* globalObject, CommonAbortReas
         return;
 
     m_commonReason = reason;
-    signalAbort(toJS(globalObject, reason));
+
+    // Pass the captured stack trace if this is a timeout signal
+    JSValue capturedStack = m_timeoutCreationStack.getValue();
+    signalAbort(toJS(globalObject, reason, capturedStack.isObject() ? jsCast<JSC::JSObject*>(capturedStack) : nullptr));
 }
 
 void AbortSignal::cleanNativeBindings(void* ref)

src/bun.js/bindings/webcore/AbortSignal.h

@@ -55,7 +55,7 @@ enum class CommonAbortReason : uint8_t {
     ConnectionClosed,
 };
 
-JSC::JSValue toJS(JSC::JSGlobalObject*, CommonAbortReason);
+JSC::JSValue toJS(JSC::JSGlobalObject*, CommonAbortReason, JSC::JSObject* capturedStack = nullptr);
 
 typedef void* AbortSignalTimeout;
 
@@ -125,6 +125,7 @@ class AbortSignal final : public RefCounted<AbortSignal>, public EventTargetWith
     size_t memoryCost() const;
 
     AbortSignalTimeout getTimeout() const { return m_timeout; }
+    const JSValueInWrappedObject& timeoutCreationStack() const { return m_timeoutCreationStack; }
 
 private:
     enum class Aborted : bool {
@@ -189,6 +190,7 @@ class AbortSignal final : public RefCounted<AbortSignal>, public EventTargetWith
     std::atomic<uint32_t> pendingActivityCount { 0 };
     uint32_t m_algorithmIdentifier { 0 };
     AbortSignalTimeout m_timeout { nullptr };
+    JSValueInWrappedObject m_timeoutCreationStack; // Captured stack at AbortSignal.timeout() call site
     uint8_t m_flags { 0 };
 };
 

test/js/bun/abort-signal-timeout-stack.test.ts

@@ -0,0 +1,51 @@
+import { expect, test, describe } from "bun:test";
+
+describe("AbortSignal.timeout stack trace", () => {
+    test("should include stack trace pointing to where AbortSignal.timeout() was called", async () => {
+        // This test verifies fix for issue #25182
+        // The stack trace should point to where AbortSignal.timeout() was called,
+        // not just where the timeout was triggered internally
+
+        async function myFunction() {
+            const signal = AbortSignal.timeout(50);
+            await new Promise((resolve, reject) => {
+                signal.addEventListener('abort', () => {
+                    reject(signal.reason);
+                });
+                setTimeout(resolve, 1000);
+            });
+        }
+
+        try {
+            await myFunction();
+            expect.unreachable("Should have thrown");
+        } catch (e: any) {
+            expect(e instanceof DOMException).toBe(true);
+            expect(e.name).toBe("TimeoutError");
+            expect(e.message).toBe("The operation timed out.");
+
+            // The stack trace should include 'myFunction' 
+            // since that's where AbortSignal.timeout() was called
+            const stack = e.stack;
+            expect(stack).toBeDefined();
+            expect(typeof stack).toBe("string");
+
+            // Check that stack trace includes the calling function
+            // This is the key fix - previously this would be empty or only have internals
+            expect(stack).toInclude("myFunction");
+        }
+    });
+
+    test("stack trace should include the test file name", async () => {
+        try {
+            const signal = AbortSignal.timeout(10);
+            await new Promise((resolve, reject) => {
+                signal.addEventListener('abort', () => reject(signal.reason));
+                setTimeout(resolve, 1000);
+            });
+        } catch (e: any) {
+            // Stack should reference this test file
+            expect(e.stack).toInclude("abort-signal-timeout-stack.test.ts");
+        }
+    });
+});