Laravel Parameter-Specific Custom Validation Messages

AppServiceProvider.php

<?php

namespace App\Providers;

use Illuminate\Support\ServiceProvider;
use App\Overrides\Illuminate\Validation\Factory as FactoryOverride;

/**
 * Class AppServiceProvider
 * @package App\Providers
 */
class AppServiceProvider extends ServiceProvider
{
    /**
     * Bootstrap any application services.
     *
     * @return void
     */
    public function boot()
    {
        $this->validatorExtensions();
    }

    /**
     * Custom extensions to the Validator Facade
     */
    protected function validatorExtensions()
    {
        //Borrowed from Illuminate\Validation\ValidationServiceProvider::registerValidationFactory()
        $this->app->singleton('validator', function ($app) {
            $validator = new FactoryOverride($app['translator'], $app);
            
            if (isset($app['db'], $app['validation.presence'])) {
                $validator->setPresenceVerifier($app['validation.presence']);
            }
            
            return $validator;
        });
    }
}

Factory.php

<?php

namespace App\Overrides\Illuminate\Validation;

use Illuminate\Validation\Factory as BaseFactory;

/**
 * Class Factory
 * @package App\Overrides\Illuminate\Validation
 */
class Factory extends BaseFactory
{
    /**
     * Override so that the override of the Validator class is returned instead of the original
     *
     * @param array $data
     * @param array $rules
     * @param array $messages
     * @param array $customAttributes
     * @return Validator|\Illuminate\Validation\Validator|mixed
     */
    protected function resolve(array $data, array $rules, array $messages, array $customAttributes)
    {
        if (is_null($this->resolver)) {
            return new Validator($this->translator, $data, $rules, $messages, $customAttributes);
        }
        
        return call_user_func($this->resolver, $this->translator, $data, $rules, $messages, $customAttributes);
    }
}

Validator.php

<?php

namespace App\Overrides\Illuminate\Validation;

use Illuminate\Support\Str;
use Illuminate\Validation\ValidationRuleParser;
use Illuminate\Validation\Validator as BaseValidator;

/**
 * Class Validator
 * @package App\Overrides\Illuminate\Validation
 */
class Validator extends BaseValidator
{
    /**
     * @var array
     */
    protected $parameters = [];
    
    /**
     * @param string $attribute
     * @param string $rule
     * @param array $parameters
     */
    protected function addFailure($attribute, $rule, $parameters)
    {
        //Cheat the process-flow a little bit, and make these values available to the override for the custom error
        //message identification process without having to alter the signature of too many parent methods
        $this->parameters = $parameters;
        
        parent::addFailure($attribute, $rule, $parameters);
    }
    
    /**
     * Most of this method mirrors the original parent, overridden to add support for parameter-specific error messages
     *
     * @param string $attribute
     * @param string $lowerRule
     * @param null $source
     * @return null|string
     */
    protected function getFromLocalArray($attribute, $lowerRule, $source = null)
    {
        //Use a placeholder indicator of the existence of parameters so that they don't need to be known in advance
        $paramPlaceholder = ':params';
        $source = $source ?: $this->customMessages;
        $keys = [
            "$attribute.$lowerRule$paramPlaceholder",
            "$attribute.$lowerRule",
            "$lowerRule$paramPlaceholder",
            $lowerRule
        ];
        
        foreach (array_keys($source) as $sourceKey) {
            list($rule, $sourceParams) = ValidationRuleParser::parse($sourceKey);
            $hasAllSourceParams = count(array_intersect($sourceParams, $this->parameters)) == count($sourceParams);
            //If the custom message key specifies parameters, replace it with out placeholder for comparison
            $testKey = preg_replace('/(.+?)(\:.+)/', "$1$paramPlaceholder", $sourceKey);
            
            foreach ($keys as $key) {
                if (Str::is($testKey, $key) && $hasAllSourceParams) {
                    $message = $source[$sourceKey];
                    
                    return $message;
                }
            }
        }
    }
}