Function loginUser

cli/command/registry/login.go:229–254

(ctx context.Context, dockerCLI command.Cli, opts loginOptions, defaultUsername, serverAddress string)

}

func loginUser(ctx context.Context, dockerCLI command.Cli, opts loginOptions, defaultUsername, serverAddress string) (msg string, _ error) {
	// Some links documenting this:
	// - https://code.google.com/archive/p/mintty/issues/56
	// - https://github.com/docker/docker/issues/15272
	// - https://mintty.github.io/ (compatibility)
	// Linux will hit this if you attempt `cat | docker login`, and Windows
	// will hit this if you attempt docker login from mintty where stdin
	// is a pipe, not a character based console.
	if (opts.user == "" || opts.password == "") && !dockerCLI.In().IsTerminal() {
		return "", errors.New("error: cannot perform an interactive login from a non-TTY device")
	}

	// If we're logging into the index server and the user didn't provide a username or password, use the device flow
	if serverAddress == registry.IndexServer && opts.user == "" && opts.password == "" {
		var err error
		msg, err = loginWithDeviceCodeFlow(ctx, dockerCLI)
		// if the error represents a failure to initiate the device-code flow,
		// then we fallback to regular cli credentials login
		if !errors.Is(err, manager.ErrDeviceLoginStartFail) {
			return msg, err
		}
		_, _ = fmt.Fprint(dockerCLI.Err(), "Failed to start web-based login - falling back to command line login...\n\n")
	}

	return loginWithUsernameAndPassword(ctx, dockerCLI, opts, defaultUsername, serverAddress)
}

func loginWithUsernameAndPassword(ctx context.Context, dockerCLI command.Cli, opts loginOptions, defaultUsername, serverAddress string) (msg string, _ error) {
	// Prompt user for credentials