BoundaryML/baml · error

failed to get function name

Error message

failed to get function name: %w

What it means

This error wraps any failure from raw_objects.CallMethod when FunctionName() asks the BAML runtime (via the C FFI) for the 'function_name' attribute of a FunctionLog. It is a pass-through wrapper: the real cause (failed FFI call, nil pointer, proto unmarshal failure, or object-response decode failure) is in the wrapped error. It means the Go client could not successfully retrieve this property from the runtime object.

Solutions

1. Read the wrapped cause via errors.Unwrap / %w output to identify whether it is 'failed to call object method function', 'object method function returned nil pointer', or a decode failure.
2. Ensure you access the FunctionLog while the function call/stream it belongs to is still valid; don't cache log objects beyond the request lifetime.
3. Align the Go client version with the BAML runtime (re-run `baml generate` so the client and engine match).
4. If the underlying error is a decode/unmarshal failure, report it upstream with your baml CLI and client versions; it indicates an FFI contract mismatch.

if fnLog == nil {
    return errors.New("function log is nil; cannot read FunctionName")
}

func isCallMethodFailure(err error) bool {
    return errors.Is(err, errCallFailed) || strings.Contains(err.Error(), "failed to call object method")
}

name, err := fnLog.FunctionName()
if err != nil {
    log.Printf("FunctionName unavailable: %v (wrapped: %v)", err, errors.Unwrap(err))
    return fmt.Errorf("baml function log inaccessible: %w", err)
}

When it happens

Trigger: Calling FunctionName() on a functionLog when the underlying runtime object pointer is invalid or already destroyed, the runtime returns an empty/nil buffer ('failed to call object method function'), or protobuf unmarshalling/decoding of the response fails.

Common situations: Iterating logs from a finished function stream after the runtime cleaned them up; stale collector/log references held across long-lived processes; version skew between the generated Go client and the BAML runtime library.

Related errors

• failed to get log type
• failed to get raw LLM response
• failed to get timing
• failed to get usage
• decodeLiteralValue: valueLiteral is nil

AI-assisted analysis of BoundaryML/baml@bd85ce9dee (2026-09-12). Data as JSON: /api/errors/adb315e994bd7cb0. Report an issue: GitHub.

Appendix: source

Thrown at engine/language_client_go/pkg/rawobjects_function_log.go:44

func (f *functionLog) Id() (string, error) {
	result, err := raw_objects.CallMethod(f, "id", nil)
	if err != nil {
		return "", fmt.Errorf("failed to get ID: %w", err)
	}

	id, ok := result.(string)
	if !ok {
		return "", fmt.Errorf("unexpected type for ID: %T", result)
	}

	return id, nil
}

func (f *functionLog) FunctionName() (string, error) {
	result, err := raw_objects.CallMethod(f, "function_name", nil)
	if err != nil {
		return "", fmt.Errorf("failed to get function name: %w", err)
	}

	name, ok := result.(string)
	if !ok {
		return "", fmt.Errorf("unexpected type for function name: %T", result)
	}

	return name, nil
}

func (f *functionLog) LogType() (string, error) {
	result, err := raw_objects.CallMethod(f, "log_type", nil)
	if err != nil {
		return "", fmt.Errorf("failed to get log type: %w", err)
	}

	logType, ok := result.(string)
	if !ok {

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