[8.x][Proposal] Add $validator->sometimesNested() to work with nested arrays

[NickSdot]

Before I send a PR I would like to introduce and propse my idea here. I consider this feature as small but helpful 'quality of life' improvement with no backwards compatibility issues.

Problem

It is not possible to use $validator->sometimes() with nested arrays inwithValidator($validator) of a FormRequest class.

Given an array/request like this (or even more nested):

public function rules(): array
    {
        return [
            "channels"    => "required|array",
            "channels.*.type"  => "required|string|min:3",
            "channels.*.value" => "required|string|distinct|min:3",
            "channels.*.description"  => "nullable|string|min:3|max:80",
        ];
    }

The value attribute can be an url or an email, depending on the value of an other field. $validator->sometimes() is not aware of the current item/index. And dot notation with an asterix is also not available. So it seems there is no flexible way to to apply specifc rules for nested arrays, to archieve this.

$validator->sometimes('channels.*.value', 'email:rfc,dns', function($item) {
  return $item->type === 'email';
});

Solution

I would not touch the existing sometimes() method for this. Hence, I would propose to add the following method to Illuminate\Validation\Validator:

    /**
     * Add conditions to a given nested field based on a Closure.
     *
     * @param  string  $parent
     * @param  string|array  $attribute
     * @param  string|array  $rules
     * @param  callable  $callback
     * @return $this
     */
    function sometimesNested(string $parent, $attribute, $rules, callable $callback)
    {
        foreach ((array) $this->getValue($parent) as $index => $item) {

            $payload = new Fluent($item);

            if ($callback($payload)) {
                foreach ((array) $attribute as $key) {
                    $this->addRules([$parent . '.' . $index . '.' . $key => $rules]);
                }
            }
        }

        return $this;
    }

How it works: Basically the functionality is pretty much the same as in $validator->sometimes(). The main difference is, that we pass a 'parent' key name as a first parameter to the method, get the values and loop trough it. If the callback returns true we add the rules based on the parent/index/key combination.

Usage

Developers would have a convinient way to access and flexible validate nested items in a FormRequest class like this:

    public function withValidator(Validator $validator)
    {
        // validate field 'value' as email, if field 'type is email
        $validator->sometimesNested('channels', 'value', 'email:rfc,dns', function ($item) {
            return $item->type === 'email';
        });

        // validate field 'value' as url, if field 'type' IS NOT email
        $validator->sometimesNested('channels', 'value', 'url', function ($item) {
            return $item->type !== 'email';
        });
    }

Please see this idea as proof of concept. Suggestions to make it even better most welcome. Keen to make a PR with tests and docs changes, if there is a chance to get this merged.

[NickSdot]

I've created a draft:
https://github.com/NickSdot/framework/tree/validator-sometimes-nested-8x

[NickSdot]

Opened a PR got it: #38385