Allow to add custom metadata to fields

AUTHORS

@@ -225,4 +225,5 @@ that much better:
  * Charanpal Dhanjal (https://github.com/charanpald)
  * Emmanuel Leblond (https://github.com/touilleMan)
  * Breeze.Kay (https://github.com/9nix00)
+ * Vicki Donchenko (https://github.com/kivistein)
 

docs/changelog.rst

@@ -19,7 +19,7 @@ Changes in 0.9.X - DEV
 - Fix for updating sorting in SortedListField. #978
 - Added __ support to escape field name in fields lookup keywords that match operators names #949
 - Support for PyMongo 3+ #946
-- Fix for issue where FileField deletion did not free space in GridFS. 
+- Fix for issue where FileField deletion did not free space in GridFS.
 - No_dereference() not respected on embedded docs containing reference. #517
 - Document save raise an exception if save_condition fails #1005
 - Fixes some internal _id handling issue. #961
@@ -30,6 +30,7 @@ Changes in 0.9.X - DEV
 - Fix for delete with write_concern {'w': 0}. #1008
 - Allow dynamic lookup for more than two parts. #882
 - Added support for min_distance on geo queries. #831
+- Allow to add custom metadata to fields #705
 
 Changes in 0.9.0
 ================

mongoengine/base/fields.py

@@ -44,7 +44,7 @@ class BaseField(object):
     def __init__(self, db_field=None, name=None, required=False, default=None,
                  unique=False, unique_with=None, primary_key=False,
                  validation=None, choices=None, verbose_name=None,
-                 help_text=None, null=False, sparse=False):
+                 help_text=None, null=False, sparse=False, custom_data=None):
         """
         :param db_field: The database field to store this field in
             (defaults to the name of the field)
@@ -71,6 +71,7 @@ class BaseField(object):
             then the default value is set
         :param sparse: (optional) `sparse=True` combined with `unique=True` and `required=False`
             means that uniqueness won't be enforced for `None` values
+        :param custom_data: (optional) Custom metadata for this field.
         """
         self.db_field = (db_field or name) if not primary_key else '_id'
 
@@ -89,6 +90,7 @@ class BaseField(object):
         self.null = null
         self.sparse = sparse
         self._owner_document = None
+        self.custom_data = custom_data
 
         # Adjust the appropriate creation counter, and save our local copy.
         if self.db_field == '_id':

tests/fields/fields.py

@@ -3818,5 +3818,22 @@ class EmbeddedDocumentListFieldTestCase(unittest.TestCase):
         # deleted from the database
         self.assertEqual(number, 1)
 
+    def test_custom_data(self):
+        """
+        Tests that custom data is saved in the field object
+        and doesn't interfere with the rest of field functionalities.
+        """
+        custom_data = {'a': 'a_value', 'b': [1, 2]}
+        class CustomData(Document):
+            a_field = IntField()
+            c_field = IntField(custom_data=custom_data)
+
+        a1 = CustomData(a_field=1, c_field=2).save()
+        self.assertEqual(2, a1.c_field)
+        self.assertFalse(hasattr(a1.c_field, 'custom_data'))
+        self.assertTrue(hasattr(CustomData.c_field, 'custom_data'))
+        self.assertEqual(custom_data['a'], CustomData.c_field.custom_data['a'])
+
+
 if __name__ == '__main__':
     unittest.main()