Laravel custom validation rule that works with not required empty field - php

Question

I have required file field which is recorded in the database as a path. I want to make it optionally required if its field in the database is null. In the update action of my controller I have set the following validation:
$this->validate(request(),[
'drawings' => 'requiredIfEmpty:'.$product->drawings.'|file|max:'. config('fox.photoMaxSize').'|mimes:pdf',
Then in app/Providers/AppServiceProvider.php I defined requiredIfEmpty validator:
Validator::extend('requiredIfEmpty',function ($attribute,$value,$parameters,$validator){
if(is_null($parameters[0]) || empty($parameters[0])){
if (is_null($value)){
return false;
}
}
return true;
});
Validator::replacer('requiredIfEmpty', function ($message, $attribute, $rule, $parameters) {
return __('The :attr is required',['attr' => $attribute]);
});
In the view _form I use laravelcollective form helper like the following for the drawings field:
<div class="form-group {{$errors->first('drawings','has-error')}}">
#if (!is_null($product->drawings))
<img src="/imgs/pdf.png" alt="{{__('PDF File')}}" title="{{__('PDF File')}}" />
<br>
#else
<img src="/imgs/empty.png" width="64" height="64" alt="{{__('Empty')}}..." title="{{__('Empty')}}..." /> <br>
#endif
{!! Form::label('drawings', __('Drawings')) !!}
{!! Form::file('drawings',['class' => 'btn btn-info','title' =>__('PDF file')]); !!}
#php ($eleE = $errors->first('drawings'))
#include('layouts.form-ele-error')
</div>
The problem is, my custom validation rule does not invoked because the field is not required and it has null value. I need any way that allows the two scenarios:
when the drawings file field is empty and $product->drawings is not null, there's no validation occured
when the drawings file field is empty and $product->drawings is null, the validation occurred.
In other words, I need a built in validation rule like requiredIf but it does not take another form field as parameter, it just take another value and it always works even the form field value is empty and the field is not required.

Answer 1

You should use the extendImplicit function to run rules when their values are empty.
Validator::extendImplicit('required_if_exists', function($attribute, $value, $parameters, $validator) {
//
});
Alternatively, in a Rule class, you should implement the ImplicitRule interface instead of Rule.
use Illuminate\Contracts\Validation\ImplicitRule;
class RequiredIfExists implements ImplicitRule {
//
}

Answer 2

I have found a solution that does not related directly with Laravel validation. It will depend on keeping original validation for the file field and keep it not required then make validation logic in the controller's action that return errorbag message if an error is found. The solution looks like the following snippet:
public function update(Request $request, Product $product)
{
$product = Product::find(request('product'));
$this->validate(request(),[
'drawings' => 'file|max:'. config('fox.photoMaxSize').'|mimes:pdf' //Original validation
]);
if(is_null($request->drawings) && is_null($product->drawings)){
return redirect()->back()->withErrors(['drawings' => __('A drawing file must be specified')]);
} //If the field is null and the database attribute is null too an error message is returned to form's file field.
...
}
However, this solution does not answer how could we define a custom validation rule that always invoked regarding-less the field is set required or not?
Reference