Method error

nix/command.go:199–238

(ctx context.Context, err error)

}

func (c *Cmd) error(ctx context.Context, err error) error {
	if err == nil {
		return nil
	}

	cmdErr := &cmdError{err: err}
	if errors.Is(err, exec.ErrNotFound) {
		cmdErr.msg = fmt.Sprintf("nix: %s not found in $PATH", c.Args[0])
	}

	switch {
	case errors.Is(ctx.Err(), context.Canceled):
		cmdErr.msg = "nix: command canceled"
	case errors.Is(ctx.Err(), context.DeadlineExceeded):
		cmdErr.msg = "nix: command timed out"
	default:
		cmdErr.msg = "nix: command error"
	}
	cmdErr.msg += ": " + c.String()

	var exitErr *exec.ExitError
	if errors.As(err, &exitErr) {
		if stderr := c.stderrExcerpt(exitErr.Stderr); len(stderr) != 0 {
			cmdErr.msg += ": " + stderr
		}
		if exitErr.Exited() {
			cmdErr.msg += fmt.Sprintf(": exit code %d", exitErr.ExitCode())
			return cmdErr
		}
		if stat, ok := exitErr.Sys().(syscall.WaitStatus); ok && stat.Signaled() {
			cmdErr.msg += fmt.Sprintf(": exit due to signal %d (%[1]s)", stat.Signal())
			return cmdErr
		}
	}

	if !errors.Is(err, ctx.Err()) {
		cmdErr.msg += ": " + err.Error()
	}
	return cmdErr
}

func (*Cmd) stderrExcerpt(stderr []byte) string {
	stderr = bytes.TrimSpace(stderr)