Merge pull request #2408 from bagerard/refactoring_remove_useless_cod…

…e_only_fields

Removed code related to Document.__only_fields

docs/changelog.rst

@@ -14,6 +14,7 @@ Development
 - Bug fix in ListField when updating the first item, it was saving the whole list, instead of
     just replacing the first item (as it's usually done) #2392
 - Add EnumField: ``mongoengine.fields.EnumField``
+- Refactoring - Remove useless code related to Document.__only_fields and Queryset.only_fields
 
 Changes in 0.20.0
 =================

mongoengine/base/document.py

@@ -64,8 +64,6 @@ def __init__(self, *args, **values):
             It may contain additional reserved keywords, e.g. "__auto_convert".
         :param __auto_convert: If True, supplied values will be converted
             to Python-type values via each field's `to_python` method.
-        :param __only_fields: A set of fields that have been loaded for
-            this document. Empty if all fields have been loaded.
         :param _created: Indicates whether this is a brand new document
             or whether it's already been persisted before. Defaults to true.
         """
@@ -80,8 +78,6 @@ def __init__(self, *args, **values):
 
         __auto_convert = values.pop("__auto_convert", True)
 
-        __only_fields = set(values.pop("__only_fields", values))
-
         _created = values.pop("_created", True)
 
         signals.pre_init.send(self.__class__, document=self, values=values)
@@ -106,10 +102,8 @@ def __init__(self, *args, **values):
         self._dynamic_fields = SON()
 
         # Assign default values to the instance.
-        # We set default values only for fields loaded from DB. See
-        # https://github.com/mongoengine/mongoengine/issues/399 for more info.
         for key, field in self._fields.items():
-            if self._db_field_map.get(key, key) in __only_fields:
+            if self._db_field_map.get(key, key) in values:
                 continue
             value = getattr(self, key, None)
             setattr(self, key, value)
@@ -758,11 +752,8 @@ def _get_collection_name(cls):
         return cls._meta.get("collection", None)
 
     @classmethod
-    def _from_son(cls, son, _auto_dereference=True, only_fields=None, created=False):
+    def _from_son(cls, son, _auto_dereference=True, created=False):
         """Create an instance of a Document (subclass) from a PyMongo SON."""
-        if not only_fields:
-            only_fields = []
-
         if son and not isinstance(son, dict):
             raise ValueError(
                 "The source SON object needs to be of type 'dict' but a '%s' was found"
@@ -817,9 +808,7 @@ def _from_son(cls, son, _auto_dereference=True, only_fields=None, created=False)
         if cls.STRICT:
             data = {k: v for k, v in data.items() if k in cls._fields}
 
-        obj = cls(
-            __auto_convert=False, _created=created, __only_fields=only_fields, **data
-        )
+        obj = cls(__auto_convert=False, _created=created, **data)
         obj._changed_fields = []
         if not _auto_dereference:
             obj._fields = fields

mongoengine/queryset/base.py

@@ -88,7 +88,6 @@ def __init__(self, document, collection):
         self._hint = -1  # Using -1 as None is a valid value for hint
         self._collation = None
         self._batch_size = None
-        self.only_fields = []
         self._max_time_ms = None
         self._comment = None
 
@@ -190,19 +189,15 @@ def __getitem__(self, key):
             if queryset._scalar:
                 return queryset._get_scalar(
                     queryset._document._from_son(
-                        queryset._cursor[key],
-                        _auto_dereference=self._auto_dereference,
-                        only_fields=self.only_fields,
+                        queryset._cursor[key], _auto_dereference=self._auto_dereference,
                     )
                 )
 
             if queryset._as_pymongo:
                 return queryset._cursor[key]
 
             return queryset._document._from_son(
-                queryset._cursor[key],
-                _auto_dereference=self._auto_dereference,
-                only_fields=self.only_fields,
+                queryset._cursor[key], _auto_dereference=self._auto_dereference,
             )
 
         raise TypeError("Provide a slice or an integer index")
@@ -719,12 +714,10 @@ def modify(
 
         if full_response:
             if result["value"] is not None:
-                result["value"] = self._document._from_son(
-                    result["value"], only_fields=self.only_fields
-                )
+                result["value"] = self._document._from_son(result["value"])
         else:
             if result is not None:
-                result = self._document._from_son(result, only_fields=self.only_fields)
+                result = self._document._from_son(result)
 
         return result
 
@@ -757,18 +750,14 @@ def in_bulk(self, object_ids):
         docs = self._collection.find({"_id": {"$in": object_ids}}, **self._cursor_args)
         if self._scalar:
             for doc in docs:
-                doc_map[doc["_id"]] = self._get_scalar(
-                    self._document._from_son(doc, only_fields=self.only_fields)
-                )
+                doc_map[doc["_id"]] = self._get_scalar(self._document._from_son(doc))
         elif self._as_pymongo:
             for doc in docs:
                 doc_map[doc["_id"]] = doc
         else:
             for doc in docs:
                 doc_map[doc["_id"]] = self._document._from_son(
-                    doc,
-                    only_fields=self.only_fields,
-                    _auto_dereference=self._auto_dereference,
+                    doc, _auto_dereference=self._auto_dereference,
                 )
 
         return doc_map
@@ -841,7 +830,6 @@ def _clone_into(self, new_qs):
             "_collation",
             "_auto_dereference",
             "_search_text",
-            "only_fields",
             "_max_time_ms",
             "_comment",
             "_batch_size",
@@ -1045,7 +1033,6 @@ def only(self, *fields):
         .. versionchanged:: 0.5 - Added subfield support
         """
         fields = {f: QueryFieldList.ONLY for f in fields}
-        self.only_fields = list(fields.keys())
         return self.fields(True, **fields)
 
     def exclude(self, *fields):
@@ -1310,10 +1297,7 @@ def to_json(self, *args, **kwargs):
     def from_json(self, json_data):
         """Converts json data to unsaved objects"""
         son_data = json_util.loads(json_data)
-        return [
-            self._document._from_son(data, only_fields=self.only_fields)
-            for data in son_data
-        ]
+        return [self._document._from_son(data) for data in son_data]
 
     def aggregate(self, pipeline, *suppl_pipeline, **kwargs):
         """Perform a aggregate function based in your queryset params
@@ -1638,9 +1622,7 @@ def __next__(self):
             return raw_doc
 
         doc = self._document._from_son(
-            raw_doc,
-            _auto_dereference=self._auto_dereference,
-            only_fields=self.only_fields,
+            raw_doc, _auto_dereference=self._auto_dereference,
         )
 
         if self._scalar:

tests/document/test_instance.py

@@ -3434,7 +3434,7 @@ class Test(Document):
         assert obj3 != dbref2
         assert dbref2 != obj3
 
-    def test_default_values(self):
+    def test_default_values_dont_get_override_upon_save_when_only_is_used(self):
         class Person(Document):
             created_on = DateTimeField(default=lambda: datetime.utcnow())
             name = StringField()