Adds support for conditional steps

[jochem-blok]

In pull request #118 revertable forms is introduced. I found no proper way to make steps conditional to the answer of the previous steps. The $step closure seems to be an option. But then reverting does not work.

See the example below:

use function Laravel\Prompts\form;
use function Laravel\Prompts\text;

$responses = form()
    ->text('What is your name?')
    ->select('What is your language?', ['PHP', 'JS'], name: 'language')
    ->add(function ($responses) {
        if ($responses['language'] == 'PHP') {
            return text("Which version?");
        }
    },
        name: 'phpversion',
    )
    ->add(function ($responses) {
        if ($responses['language'] == 'JS') {
            return text("Which os?");
        }
    },
        name: 'os'
    )->confirm('Are you sure?')
    ->submit();

The option ignoreWhenReverting seems to be an option, but it that simply skips the step. So conditional forms are hard.

In the example below I rewrote the above example with the suggested change. And now everything seems to work fine.

use function Laravel\Prompts\form;
use function Laravel\Prompts\text;

$responses = form()
    ->text('What is your name?')
    ->select('What is your language?', ['PHP', 'JS'], name: 'language')
    ->add(function () {
            return text("Which version?");
        },
        name: 'phpversion',
        condition: function ($responses) {
            return $responses['language'] == 'PHP';
        }
    )
    ->add(function () {
            return text("Which os?");
        },
        name: 'os',
        condition: function ($responses) {
            return $responses['language'] == 'JS';
        }
    )->confirm('Are you sure?')
    ->submit();

[taylorotwell]

Drafting pending review from @jessarcher

[taylorotwell]

Should this instead be something like addIf where the condition can be the first argument?

[jochem-blok]

Is this something I should answer? This is my first PR :)

I am happy to implement the suggested change.

[devajmeireles]

Is this something I should answer? This is my first PR :)

I am happy to implement the suggested change.

He's asking a general question, to all PR participants (including you), and also to the main maintainer, @jessarcher

[jessarcher]

Having the condition as the first argument reads nicely.

I think the ultimate API would be a when method that gets the form instance:

$responses = form()
    ->text('First question...')
    ->when($condition, fn ($form) => $form
        ->text('Conditional question')
        ->text('Another conditional question')
    );

But I had a quick play around and it's not straight-forward to implement with the revert behavior.

[jochem-blok]

Following your reasoning Taylor why isn't addScrollable (because scroll is also an option) added? Having each optional parameter in a function would create a cartesian product.

And with the option to use named arguments I don't see the need for moving the condition to the first argument (and remove the optional behaviour).

How do we advance in this? Jess is trying to implement the same effect with another solution.

[jessarcher]

Following your reasoning Taylor why isn't addScrollable (because scroll is also an option) added? Having each optional parameter in a function would create a cartesian product.

I'd say it's because the conditional aspect, when present, is important to read before the specific configuration of the step. It follows the way a typical if statement reads (if, then...) and matches things like the abort_if function in the framework.

How do we advance in this? Jess is trying to implement the same effect with another solution.

I think Taylor would be happy to merge if you added a new addIf($condition, ...) method, instead of changing the add method.

[jochem-blok]

I implemented the new method and changed the test cases. Please review :)