ignore any number of leading underscores when converting from snake case to camel case (ie. leave '_username' unchanged)

Author: lsmith77

Normalizer/CamelKeysNormalizer.php

@@ -75,8 +75,17 @@ private function normalizeString($string)
             return $string;
         }
 
-        return preg_replace_callback('/_([a-zA-Z0-9])/', function ($matches) {
+        if (preg_match('/^(_+)(.*)/', $string, $matches)) {
+            $underscorePrefix = $matches[1];
+            $string = $matches[2];
+        } else {
+            $underscorePrefix = '';
+        }
+
+        $string = preg_replace_callback('/_([a-zA-Z0-9])/', function ($matches) {
             return strtoupper($matches[1]);
         }, $string);
+
+        return $underscorePrefix.$string;
     }
 }

Tests/Normalizer/CamelKeysNormalizerTest.php

@@ -50,6 +50,8 @@ public function normalizeProvider()
                     'foo1ar' => array('foo_bar'),
                 ),
             ),
+            // ignore leading underscores
+            array(array('__username' => 'foo', '_password' => 'bar', '_foo_bar' => 'foobar'), array('__username' => 'foo', '_password' => 'bar', '_fooBar' => 'foobar')),
         );
     }
 }