Support single command app

[jvalkeal]

There are times when user wants to create an app which:

1. Don't have interactive mode
2. Has only one command

Currently you're forced to have something like myapp mycommand --option xxx. It'd be convenient to be able to have an app which works as myapp --option xxx.

[jvalkeal]

While looking into this realised that there is already a hack to do this in not so obvious way. This issue should be changed to make this easy to config.

Define a command:

@Command
public class DemoCommand {

	@Command
	public String hi(@Option String arg) {
		return String.format("hi arg='%s'", arg);
	}
}

Customise NonInteractiveShellRunner to tweak command in use:

@SpringBootApplication
@CommandScan
public class DemoApplication {

    private static final String SINGLE_QUOTE = "\'";
    private static final String DOUBLE_QUOTE = "\"";

	private static boolean isQuoted(String str) {
		if (str == null) {
			return false;
		}
		return str.startsWith(SINGLE_QUOTE) && str.endsWith(SINGLE_QUOTE)
				|| str.startsWith(DOUBLE_QUOTE) && str.endsWith(DOUBLE_QUOTE);
	}

	private Function<ApplicationArguments, List<String>> commandsFromInputArgs = args -> {
		if (args.getSourceArgs().length == 0) {
			Collections.singletonList("hi");
		}
		// re-quote if needed having whitespace
		String raw = Arrays.stream(args.getSourceArgs())
			.map(a -> {
				if (!isQuoted(a) && StringUtils.containsWhitespace(a)) {
					return "\"" + a + "\"";
				}
				return a;
			})
			.collect(Collectors.joining(" "));
		return Collections.singletonList("hi " + raw);
	};

	@Bean
	public NonInteractiveShellRunnerCustomizer runnerCustomizer() {
		return runner -> {
			runner.setCommandsFromInputArgs(commandsFromInputArgs);
		};
	}

	public static void main(String[] args) {
		SpringApplication.run(DemoApplication.class, args);
	}

}

Disable interactive/script runners:

spring:
  shell:
    interactive:
      enabled: false
    script:
      enabled: false

$ java -jar build/libs/demo-0.0.1-SNAPSHOT.jar --arg xxx

hi arg='xxx'

[jvalkeal]

Current main branch has a skeleton sample https://github.com/spring-projects/spring-shell/tree/main/spring-shell-samples/spring-shell-sample-catalog. Branch 3.1.x don't have split sample structure so it can't be shown there but concept on main is same.

Docs for this are here https://github.com/spring-projects/spring-shell/blob/main/spring-shell-docs/src/main/asciidoc/using-shell-customization-singlecommand.adoc