Error.appendStackTrace: don't abort when stackTraceLimit is unset

src/jsc/bindings/FormatStackTraceForJS.cpp

@@ -668,11 +668,11 @@ JSC_DEFINE_HOST_FUNCTION(errorConstructorFuncAppendStackTrace, (JSC::JSGlobalObj
         return {};
     }
 
-    if (!destination->stackTrace()) {
+    if (!destination->stackTrace() && globalObject->stackTraceLimit()) {
         destination->captureStackTrace(vm, globalObject, 1);
     }
 
-    if (source->stackTrace()) {
+    if (source->stackTrace() && destination->stackTrace()) {
         destination->stackTrace()->appendVector(*source->stackTrace());
         source->stackTrace()->clear();
     }

test/js/node/v8/capture-stack-trace.test.js

@@ -1121,3 +1121,28 @@ test("lazy error-info materialization does not store an empty stack value when t
   });
   expect(exitCode).toBe(0);
 });
+
+test("Error.appendStackTrace does not abort when stackTraceLimit is not a number", async () => {
+  const src = `
+    Error.stackTraceLimit = undefined;
+    const a = new Error();
+    const b = new Error();
+    Error.appendStackTrace(a, b);
+
+    Error.stackTraceLimit = 10;
+    const c = new Error();
+    delete Error.stackTraceLimit;
+    const d = new Error();
+    Error.appendStackTrace(c, d);
+
+    process.stdout.write("ok");
+  `;
+  await using proc = Bun.spawn({
+    cmd: [bunExe(), "-e", src],
+    env: bunEnv,
+    stderr: "pipe",
+  });
+  const [stdout, stderr, exitCode] = await Promise.all([proc.stdout.text(), proc.stderr.text(), proc.exited]);
+  expect({ stdout, stderr, signalCode: proc.signalCode }).toEqual({ stdout: "ok", stderr: "", signalCode: null });
+  expect(exitCode).toBe(0);
+});