Added ability to customise validation errors (#113)

* Added ability to customise validation errors

* Added documentation for validation
Made validationErrorMessages a method that can be overridden

* Update Readme.md

* Update Field.php

Readme.md

@@ -461,6 +461,28 @@ When you execute a mutation, it will return any validation errors that occur. Si
 	}
 ```
 
+
+The validation errors returned can be customised by overriding the `validationErrorMessages` method on the mutation. This method should return an array of custom validation messages in the same way documented by Laravel's validation. For example, to check an `email` argument doesn't conflict with any existing data, you could perform the following -
+
+Note: the keys should be in `field_name`.`validator_type` format so you can return specific errors per validation type.
+
+
+````php
+
+    public function validationErrorMessages ($args = []) 
+    {
+        return [
+            'name.required' => 'Please enter your full name',
+            'name.string' => 'Your name must be a valid string',
+            'email.required' => 'Please enter your email address',
+            'email.email' => 'Please enter a valid email address',
+            'email.exists' => 'Sorry, this email address is already in use',                     
+        ];
+    }
+
+````
+
+
 #### File uploads
 
 For uploading new files just use `UploadType`. This support of uploading files is base on https://github.com/jaydenseric/graphql-multipart-request-spec

src/Rebing/GraphQL/Support/Field.php

@@ -36,6 +36,17 @@ public function args()
         return [];
     }
 
+    /**
+     * Define custom Laravel Validator messages as per Laravel 'custom error messages'
+     * @param array $args submitted arguments
+     * @return array
+     */
+    public function validationErrorMessages(array $args = [])
+    {
+        return [];
+    }
+
+
     protected function rules(array $args = [])
     {
         return [];
@@ -155,7 +166,11 @@ protected function getResolver()
                 $rules = call_user_func_array([$this, 'getRules'], [$args]);
                 if(sizeof($rules))
                 {
-                    $validator = Validator::make($args, $rules);
+
+                    // allow our error messages to be customised
+                    $messages = $this->validationErrorMessages($args);
+
+                    $validator = Validator::make($args, $rules, $messages);
                     if($validator->fails())
                     {
                         throw with(new ValidationError('validation'))->setValidator($validator);