Improve default parser to accept boolean options without values

[fmbenhassine]

This was initially reported by @ThomasVitale in #1262

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Furthermore, when providing the option at execution time, a value is also required. This bit is mentioned in the docs, but it would be great to highlight that in the migration guide as a breaking change since it completely change the user experience.

It's common for CLIs to pass boolean options to a command without a value, meaning it's "true". Any chance the previous behaviour could be restored? This breaking change doesn't affect only developers when upgrading to 4.0, but also all users of CLIs implemented with Spring Shell, having to change commands like:

mycli test --clean

to:

mycli test --clean true

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As of 4.0.0, the default parser expects all options to have a value, even boolean ones, and the reason was explained in #1248.

However, this seems to hinder things and affect the user experience.

[czpilar]

Fixed in PR #1305

package org.springframework.shell.samples.helloworld.boot;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.shell.core.command.annotation.Command;
import org.springframework.shell.core.command.annotation.Option;

@SpringBootApplication
public class SpringShellApplication {

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

	@Command(name = "test")
	public void test(@Option(longName = "clean") boolean clean) {
		System.out.println("Hello " + clean + "!");
	}

}

[czpilar]

@fmbenhassine It could be added to 4.0.1 if it is not too late.

[fmbenhassine]

@czpilar Perfect! No it's not too late, I will include it in 4.0.1. Thank you very much for your help!