[6.x] Allow formatting an implicit attribute using a closure (#31246)

*          allow formatting an implicit attribute using a closure

src/Illuminate/Validation/Concerns/FormatsMessages.php

@@ -250,7 +250,9 @@ public function getDisplayableAttribute($attribute)
         // an implicit attribute we will display the raw attribute's name and not
         // modify it with any of these replacements before we display the name.
         if (isset($this->implicitAttributes[$primaryAttribute])) {
-            return $attribute;
+            return ($formatter = $this->implicitAttributesFormatter)
+                            ? $formatter($attribute)
+                            : $attribute;
         }
 
         return str_replace('_', ' ', Str::snake($attribute));

src/Illuminate/Validation/Validator.php

@@ -97,6 +97,13 @@ class Validator implements ValidatorContract
      */
     protected $implicitAttributes = [];
 
+    /**
+     * The callback that should be used to format the attribute.
+     *
+     * @var callable|null
+     */
+    protected $implicitAttributesFormatter;
+
     /**
      * The cached data for the "distinct" rule.
      *
@@ -1112,6 +1119,19 @@ public function addCustomAttributes(array $customAttributes)
         return $this;
     }
 
+    /**
+     * Set the callback that used to format an implicit attribute..
+     *
+     * @param  callable|null  $formatter
+     * @return $this
+     */
+    public function setImplicitAttributesFormatter(callable $formatter = null)
+    {
+        $this->implicitAttributesFormatter = $formatter;
+
+        return $this;
+    }
+
     /**
      * Set the custom values on the validator.
      *

tests/Integration/Validation/ValidatorTest.php

@@ -32,6 +32,23 @@ public function testExists()
         $this->assertFalse($validator->passes());
     }
 
+    public function testImplicitAttributeFormatting()
+    {
+        $translator = new Translator(new ArrayLoader, 'en');
+        $translator->addLines(['validation.string' => ':attribute must be a string!'], 'en');
+        $validator = new Validator($translator, [['name' => 1]], ['*.name' => 'string']);
+
+        $validator->setImplicitAttributesFormatter(function ($attribute) {
+            [$line, $attribute] = explode('.', $attribute);
+
+            return sprintf('%s at line %d', $attribute, $line + 1);
+        });
+
+        $validator->passes();
+
+        $this->assertEquals('name at line 1 must be a string!', $validator->getMessageBag()->all()[0]);
+    }
+
     protected function getValidator(array $data, array $rules)
     {
         $translator = new Translator(new ArrayLoader, 'en');