Raise AlreadyCreatedError when modifying pk of created document

tests/test_document.py

@@ -419,6 +419,28 @@ class Parent(Document):
         assert jane.id != john.id
         assert jane.name == 'John Doe'
 
+    def test_modify_pk_field(self):
+
+        @self.instance.register
+        class User(Document):
+            primary_key = fields.ObjectIdField(attribute='_id', default=ObjectId)
+            name = fields.StrField()
+
+        john = User()
+        john.primary_key = ObjectId()
+        john.from_mongo({'name': 'John Doc'})
+        assert john.is_created
+        with pytest.raises(exceptions.AlreadyCreatedError):
+            john.primary_key = ObjectId()
+        with pytest.raises(exceptions.AlreadyCreatedError):
+            john['primary_key'] = ObjectId()
+        with pytest.raises(exceptions.AlreadyCreatedError):
+            del john.primary_key
+        with pytest.raises(exceptions.AlreadyCreatedError):
+            del john['primary_key']
+        with pytest.raises(exceptions.AlreadyCreatedError):
+            john.update({'primary_key': ObjectId()})
+
 
 class TestConfig(BaseTest):
 

umongo/__init__.py

@@ -20,6 +20,7 @@
     ValidationError,
     UpdateError,
     DeleteError,
+    AlreadyCreatedError,
     NotCreatedError,
     NoneReferenceError,
     UnknownFieldInDBError,
@@ -56,6 +57,7 @@
     'ValidationError',
     'UpdateError',
     'DeleteError',
+    'AlreadyCreatedError',
     'NotCreatedError',
     'NoneReferenceError',
     'UnknownFieldInDBError',

umongo/document.py

@@ -5,7 +5,7 @@
 
 from .abstract import BaseDataObject
 from .data_proxy import missing
-from .exceptions import (NotCreatedError, NoDBDefinedError,
+from .exceptions import (AlreadyCreatedError, NotCreatedError, NoDBDefinedError,
                          AbstractDocumentError, DocumentDefinitionError)
 from .template import Implementation, Template, MetaImplementation
 from .data_objects import Reference
@@ -233,14 +233,13 @@ def to_mongo(self, update=False):
                        update payload instead of containing the entire document
         """
         if update and not self.is_created:
-            raise NotCreatedError('Must create the document before'
-                                  ' using update')
+            raise NotCreatedError('Must create the document before using update')
         return self._data.to_mongo(update=update)
 
     def update(self, data):
-        """
-        Update the document with the given data.
-        """
+        """Update the document with the given data."""
+        if self.is_created and self.pk_field in data.keys():
+            raise AlreadyCreatedError("Can't modify id of a created document")
         self._data.update(data)
 
     def dump(self):
@@ -273,11 +272,21 @@ def __getitem__(self, name):
         value = self._data.get(name)
         return value if value is not missing else None
 
+    def __setitem__(self, name, value):
+        if self.is_created and name == self.pk_field:
+            raise AlreadyCreatedError("Can't modify id of a created document")
+        self._data.set(name, value)
+
     def __delitem__(self, name):
+        if self.is_created and name == self.pk_field:
+            raise AlreadyCreatedError("Can't modify id of a created document")
         self._data.delete(name)
 
-    def __setitem__(self, name, value):
-        self._data.set(name, value)
+    def __getattr__(self, name):
+        if name[:2] == name[-2:] == '__':
+            raise AttributeError(name)
+        value = self._data.get(name, to_raise=AttributeError)
+        return value if value is not missing else None
 
     def __setattr__(self, name, value):
         # Try to retrieve name among class's attributes and __slots__
@@ -288,20 +297,18 @@ def __setattr__(self, name, value):
         if name in self.__real_attributes:
             object.__setattr__(self, name, value)
         else:
+            if self.is_created and name == self.pk_field:
+                raise AlreadyCreatedError("Can't modify id of a created document")
             self._data.set(name, value, to_raise=AttributeError)
 
-    def __getattr__(self, name):
-        if name[:2] == name[-2:] == '__':
-            raise AttributeError(name)
-        value = self._data.get(name, to_raise=AttributeError)
-        return value if value is not missing else None
-
     def __delattr__(self, name):
         if not self.__real_attributes:
             type(self).__real_attributes = dir(self)
         if name in self.__real_attributes:
             object.__delattr__(self, name)
         else:
+            if self.is_created and name == self.pk_field:
+                raise AlreadyCreatedError("Can't modify pk of a created document")
             self._data.delete(name, to_raise=AttributeError)
 
     # Callbacks

umongo/exceptions.py

@@ -38,6 +38,10 @@ class DeleteError(UMongoError):
     """Error while deleting document"""
 
 
+class AlreadyCreatedError(UMongoError):
+    """Modifying id of an already created document"""
+
+
 class NotCreatedError(UMongoError):
     """Document does not exist in database"""