add lowerCamelCase

README.rst

@@ -145,6 +145,35 @@ The `my_key` field would not have its data changed:
 
     {"myKey": {"do_not_change": 1}}
 
+=============
+Use lower camel case style
+=============
+
+You can also specify lowerCamelCase behaviour, in which first letter will be always in lower case.
+For example:
+
+.. code-block:: python
+
+    data = {"_some_key": 1}
+
+Would become:
+
+.. code-block:: python
+
+    {"someKey": 1}
+
+By default, the package not uses lowerCamelCase behaviour. To use it, specify it in your django settings file.
+
+.. code-block:: python
+
+    REST_FRAMEWORK = {
+        # ...
+        'JSON_UNDERSCOREIZE': {
+            'lower_camel_case': True,
+        },
+        # ...
+    }
+
 =============
 Running Tests
 =============

djangorestframework_camel_case/settings.py

@@ -8,7 +8,7 @@
 DEFAULTS = {
     "RENDERER_CLASS": "rest_framework.renderers.JSONRenderer",
     "PARSER_CLASS": "rest_framework.parsers.JSONParser",
-    "JSON_UNDERSCOREIZE": {"no_underscore_before_number": False, "ignore_fields": None},
+    "JSON_UNDERSCOREIZE": {"no_underscore_before_number": False, "ignore_fields": None, "lower_camel_case": False},
 }
 
 # List of settings that may be in string import notation.

djangorestframework_camel_case/util.py

@@ -9,20 +9,13 @@
 
 from rest_framework.utils.serializer_helpers import ReturnDict
 
-camelize_re = re.compile(r"[a-z0-9]?_[a-z0-9]")
-
-
-def underscore_to_camel(match):
-    group = match.group()
-    if len(group) == 3:
-        return group[0] + group[2].upper()
-    else:
-        return group[1].upper()
+camelize_re = re.compile("_[a-z0-9]")
 
 
 def camelize(data, **options):
     # Handle lazy translated strings.
     ignore_fields = options.get("ignore_fields") or ()
+    lower_camel_case = options.get("lower_camel_case") or False
     if isinstance(data, Promise):
         data = force_str(data)
     if isinstance(data, dict):
@@ -34,7 +27,9 @@ def camelize(data, **options):
             if isinstance(key, Promise):
                 key = force_str(key)
             if isinstance(key, str) and "_" in key:
-                new_key = re.sub(camelize_re, underscore_to_camel, key)
+                new_key = re.sub(camelize_re, lambda match: match.group()[1].upper(), key)
+                if new_key and lower_camel_case:
+                    new_key = f'{new_key[0].lower()}{new_key[1:]}'
             else:
                 new_key = key
             if key not in ignore_fields and new_key not in ignore_fields:

tests.py

@@ -38,6 +38,7 @@ def test_under_to_camel_keys(self):
             "mix_123123a_and_letters": 7,
             "mix_123123aa_and_letters_complex": 8,
             "no_underscore_before123": 9,
+            "": 10,
         }
         output = {
             "twoWord": 1,
@@ -49,9 +50,37 @@ def test_under_to_camel_keys(self):
             "mix123123aAndLetters": 7,
             "mix123123aaAndLettersComplex": 8,
             "noUnderscoreBefore123": 9,
+            "": 10,
         }
         self.assertEqual(camelize(data), output)
 
+    def test_under_to_camel_keys_with_lower_camel_case(self):
+        data = {
+            "_two_word": 1,
+            "_long_key_with_many_underscores": 2,
+            "_only_1_key": 3,
+            "_only_one_letter_a": 4,
+            "_b_only_one_letter": 5,
+            "_only_c_letter": 6,
+            "_mix_123123a_and_letters": 7,
+            "_mix_123123aa_and_letters_complex": 8,
+            "_no_underscore_before123": 9,
+            "": 10,
+        }
+        output = {
+            "twoWord": 1,
+            "longKeyWithManyUnderscores": 2,
+            "only1Key": 3,
+            "onlyOneLetterA": 4,
+            "bOnlyOneLetter": 5,
+            "onlyCLetter": 6,
+            "mix123123aAndLetters": 7,
+            "mix123123aaAndLettersComplex": 8,
+            "noUnderscoreBefore123": 9,
+            "": 10,
+        }
+        self.assertEqual(camelize(data, lower_camel_case=True), output)
+
     def test_tuples(self):
         data = {"multiple_values": (1, 2), "data": [1, 3, 4]}
         output = {"multipleValues": [1, 2], "data": [1, 3, 4]}