Single + Default Command

What if my application is only going to have a single command? I would love the ability to define a configuration property that says I only have a single command and here is what it is. When I run the program I am dropped into the shell and whatever I type is now the argument to the single default command.

This came up when building a Spring Shell + Spring AI application that interfaces with Open AI's GPT-4. I have included the rep for reference below.

https://github.com/danvega/sbdocs

i think u can see this https://docs.spring.io/spring-shell/reference/customization/singlecommand.html

Update docs

Ups, linked and closed wrong issue

Little clarification when I discussed with Dan. This is about interactive shell and having that one command there without having a need to define that command.

Hi~ What's the progress on this issue? I'm eager to find out how to specify a default command in interactive mode, just like the single-command in non-interactive mode.

@danvega

@danvega After some exploration, I've found a way to implement a "default command" — by customizing org.springframework.shell.Shell and overriding its evaluate method. The original evaluate method:

So, what we need to do is modify the behavior of evaluate to use a default command for every input (except special commands):

I've defined the default command as chat:

@Command(command = "chat", description = "Chat with the assistant")
public void chat(@Option(longNames = "query", shortNames = 'q', description = "The message to send", required = true, arity = ONE_OR_MORE)
                 String[] words) {
    String userQuery = String.join(" ", words);

    try {
        streamChat(userQuery);
    } catch (Exception e) {
        e.printStackTrace(System.err);
    }
}

Customize Shell to change the behavior of evaluate:

/**
 * @see org.springframework.shell.Shell
 * @see org.springframework.shell.boot.SpringShellAutoConfiguration
 */
@Primary
@Component
public class MyShell extends Shell {

    // This is just an example; you may obtain the current system’s command set to replace it.
    private static final Set<String> INTERNAL_COMMANDS = Set.of("help", "exit", "quit");

    public MyShell(ResultHandlerService resultHandlerService,
                   CommandCatalog commandRegistry,
                   Terminal terminal,
                   ShellContext shellContext,
                   ExitCodeMappings exitCodeMappings) {
        super(resultHandlerService, commandRegistry, terminal, shellContext, exitCodeMappings);
    }

    @Override
    protected Object evaluate(Input input) {
        List<String> words = input.words();

        if (words.isEmpty() || words.getFirst().isEmpty()) {
            return super.evaluate(input);
        }

        // If the first word is an internal command (like `help`, `exit`), execute the original logic directly
        if (INTERNAL_COMMANDS.contains(words.getFirst())) {
            return super.evaluate(input);
        }

        // Use the `chat` command to process the input text
        String rawText = input.rawText();
        return super.evaluate(() -> "chat " + rawText);
    }
}

Running example as shown below. You can see that if the input does not match INTERNAL_COMMANDS, it will default to using the chat command to process the input:

Now there's another issue: because there's no matching command, the "highlighting feature" will treat this as an erroneous input and display it in red, which looks odd. Fortunately, we can also customize the "highlighting feature":

/**
 * @see org.springframework.shell.boot.LineReaderAutoConfiguration#lineReader()
 */
public class MyHighlighter implements Highlighter {

    // This is just an example; you may obtain the current system’s command set to replace it.
    private static final Set<String> INTERNAL_COMMANDS = Set.of("help", "exit", "quit");

    private final CommandCatalog commandRegistry;

    public MyHighlighter(CommandCatalog commandRegistry) {
        this.commandRegistry = commandRegistry;
    }

    @Override
    public AttributedString highlight(LineReader reader, String buffer) {
        String trimmedBuffer = buffer.trim();

        if (trimmedBuffer.isEmpty()) {
            return new AttributedString(buffer);
        }

        String[] words = trimmedBuffer.split(" ", 2);

        // If the first word of the input is not an internal command (like `help`, `exit`), then it's using the `chat` command
        if (!INTERNAL_COMMANDS.contains(words[0])) {
            // You can choose a style you like; here I'm using foreground color CYAN
            return new AttributedString(buffer, AttributedStyle.DEFAULT.foreground(AttributedStyle.CYAN));
        }

        // Copy from org.springframework.shell.boot.LineReaderAutoConfiguration#lineReader()
        int len = 0;
        String best = null;
        // Find the longest matching command
        for (String command : commandRegistry.getRegistrations().keySet()) {
            if (buffer.startsWith(command) && command.length() > len) {
                len = command.length();
                best = command;
            }
        }

        if (best != null) {
            return new AttributedStringBuilder(buffer.length())
                    .append(best, AttributedStyle.BOLD)
                    .append(buffer.substring(len))
                    .toAttributedString();
        } else {
            return new AttributedString(buffer, AttributedStyle.DEFAULT.foreground(AttributedStyle.RED));
        }
    }
}

Customize JLine's LineReader to use MyHighlighter for the "highlighting feature":

/**
 * @see org.springframework.shell.boot.LineReaderAutoConfiguration;
 */
@Configuration
public class LineReaderConfig {

    private final LineReader lineReader;

    private final CommandCatalog commandRegistry;

    public LineReaderConfig(LineReader lineReader, CommandCatalog commandRegistry) {
        this.lineReader = lineReader;
        this.commandRegistry = commandRegistry;
    }

    @PostConstruct
    public void customHighlighter() {
        if (lineReader instanceof LineReaderImpl lineReaderImpl) {
            var highlighter = new MyHighlighter(commandRegistry);
            lineReaderImpl.setHighlighter(highlighter);
        }
    }
}

Final result:

My Java version: 25.0.2
My Spring Shell version: 3.4.1

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Single + Default Command #1067

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