Create built-in Laravel unique_with validation rule

[MatteoT92]

Hi everyone.
I ask you if is possible implementing an rule built-in as actual unique rule but applied on composite key (unique or primary)?

[shaedrich]

You could make the $column property of \Illuminate\Validation\Rules\DatabaseRule plural and an array or string|string[]:

framework/src/Illuminate/Validation/Rules/DatabaseRule.php

Lines 48 to 53 in 6bed63f

	public function __construct($table, $column = 'NULL')
	{
	$this->column = $column;
	$this->table = $this->resolveTableName($table);
	}

Technically, the \Illuminate\Validation\Rules\Unique::ignoreModel() method could take case of that automatically:

framework/src/Illuminate/Validation/Rules/Unique.php

Lines 53 to 59 in 6bed63f

	public function ignoreModel($model, $idColumn = null)
	{
	$this->idColumn = $idColumn ?? $model->getKeyName();
	$this->ignore = $model->{$this->idColumn};
	return $this;
	}

but as the docs state, Laravel doesn't support composite keys natively, so I'm not surprise, that it doesn't.

Eloquent requires each model to have at least one uniquely identifying "ID" that can serve as its primary key. "Composite" primary keys are not supported by Eloquent models. However, you are free to add additional multi-column, unique indexes to your database tables in addition to the table's uniquely identifying primary key.

It's already possible to use \Illuminate\Validation\Rules\Unique::using():

use Illuminate\Validation\Rule;

class MyRequest extends FormRequest
{
    public function rules(): array
        return [
            'user_id' => [ Rule::unique(User::class, 'id')->using(function($query) use($user) {
                $query->where([ 'id' => $this->user_id, 'name' => $this->user_name ]);
            }) ],
        ];
    }
}

You might customize the error message in that case, which is "The user id has already been taken."

But the thing is: The Laravel validation rules are built to validate each field separately, so this would break a bit with that convention.