GopeedLab/gopeed · error

promise rejected

Error message

promise rejected

What it means

exportJSError (pkg/download/engine/engine.go:203-218) converts a JS rejection value into a Go error. When the promise rejects with undefined or null (or the Go side passes a nil goja.Value), there is no message or stack to extract, so it falls back to the generic 'promise rejected'. Any richer information (Error object with .stack, a string, an error export) would have been preserved.

Source

Thrown at pkg/download/engine/engine.go:210

	<-done
	return engine
}

func Run(script string) (value any, err error) {
	engine := NewEngine(nil)
	return engine.RunString(script)
}

func exportJSValue(value goja.Value) any {
	if value == nil {
		return nil
	}
	return value.Export()
}

func exportJSError(value goja.Value) error {
	if value == nil || goja.IsUndefined(value) || goja.IsNull(value) {
		return errors.New("promise rejected")
	}
	if err, ok := value.Export().(error); ok {
		return err
	}
	stack := value.String()
	if ro, ok := value.(*goja.Object); ok {
		stackVal := ro.Get("stack")
		if stackVal != nil && stackVal.String() != "" {
			stack = stackVal.String()
		}
	}
	return errors.New(stack)
}

func callExportedFunction(fn func(goja.FunctionCall) goja.Value, args ...goja.Value) (ret goja.Value, err error) {
	defer func() {
		if r := recover(); r != nil {
			switch v := r.(type) {

View on GitHub (pinned to 7b7327ffb3)

Solutions

1. Re-run the failing script with logging or a try/catch wrapper that stringifies the rejection: p.catch(e => console.log(String(e), e && e.stack))
2. Change script code to always reject/throw with an Error: throw new Error('reason') or Promise.reject(new Error('reason')) so exportJSError can carry the message/stack
3. Temporarily wrap the script: Promise.resolve(scriptResult).catch(e => { throw e === undefined ? new Error('rejected with undefined') : e })
4. Once the real message appears, fix the underlying script bug

Example fix

// before (script)
async function resolve() { throw undefined }

// after (script)
async function resolve() { throw new Error('resolve: no stream url found') }

// Script-side: reject with a reason so the Go side gets a real message
// Promise.reject(new Error('why')) instead of Promise.reject()

// Script-side guard:
function fail(msg) { throw msg == null ? new Error('failure (no reason given)') : msg }

_, err := engine.RunString(script)
if err != nil && err.Error() == "promise rejected" {
    // rejection carried undefined/null: instrument the script's .catch to surface the cause
}

When it happens

Trigger: Script calls Promise.reject() with no argument; 'throw undefined' / 'throw null' inside an async function or promise chain; reject(void 0) in minified/bundled code; calling a rejection callback with no args.

Common situations: Bundled/minified resolver scripts that throw bare undefined; scripts copied from environments where throw; undefined is idiomatic; debugging blind because the real cause is lost — the generic message means 'the script failed but gave no reason'.

Related errors

• promise.then is not callable
• promise.then is not callable
• promise rejected
• panic: %v
• EVALUATION_FAILED

AI-assisted analysis of GopeedLab/gopeed@7b7327ffb3 (2026-08-16). Data as JSON: /api/errors/2a95b0701c2237e1. Report an issue: GitHub.