change arity of parameters based on options ?

[mand...@redhat.com]

Hey,

Trying to figure out how best to do the following in jbang:

Normally jbang has a parameter:

@CommandLine.Parameters(index = "0", arity = "1", description = "A file with java code or if named .jsh will be run with jshell")
String scriptOrFile; 

meaning for all cases a file is required.

Now, I would like to add an option `-i` which says - no need to have a file and enter interactive mode.

How would you go about adding such option that mades the arity 0 for "scriptOrFile" but otherwise should be arity 1 ?

[Remko Popma]

The simplest thing to do is to change the arity of the positional parameter from 1 to "0..1" and do the validation in the logic of the command.

The implementation of this validation could look like this:

```java 

@Spec CommandSpec spec;

public void run() { // or call 

  if (!interactive && scriptOrFile == null) {

    throw new ParameterException(spec.commandLine(),

        "Missing required file with Java code.");

  }

```

I would also change the description of the positional parameter  to add a sentence like "Ignored when --interactive is specified."

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[Max Rydahl Andersen]

Hi Remko,

The issue is that the help now makes it show as not required when it really is for 99% of cases....but I guess I can't have it all :)

/max

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/max
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[Andres Almiray]

Hi Max,

I use composite with include and exclude sections. JReleaser release command shows how it can be done. —auto-config and all other options related to it are exclusive from the “main” use case. No custom validation logic was needed in this way. 

https://github.com/jreleaser/jreleaser/blob/91d94f7b5cb7c84aa0e290d28bf662b87758d5a4/apps/jreleaser/src/main/java/org/jreleaser/cli/Release.java

Sent from my primitive tricorder

On 7 Feb 2022, at 9:52, Max Rydahl Andersen <mand...@redhat.com> wrote:



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[Remko Popma]

Max,

Other than Andres' solution, if the issue is that the synopsis now shows `command -xyz [<scriptOrFile>]`, 

where you want to show `command -xyz <scriptOrFile>`, there are several solutions.

The simplest solution is to use a custom synopsis (https://picocli.info/#_custom_synopsis).

This has the drawback that any subsequent changes require you to also update the custom synopsis, which is fragile.

A less simple solution is to parse in two phases, similar to what is documented here: https://picocli.info/#_controlling_the_locale

The idea is that you use the first phase to determine whether the --interactive flag was set, and depending on that

you would create a different model (e.g. add the `scriptOrFile` positional parameter or leave it out, or something like that.)

This is quite a bit of work though...

Another option is to just live with the truth. :-)

If the `scriptOrFile` positional parameter is not mandatory in 1% of the cases, it is not always mandatory.

And the description of the `scriptOrFile` positional parameter and the --interactive option could clarify when the positional parameter becomes mandatory.

Hope this helps,

:-)

Remko