Made field validation lazier

mongoengine/base.py

@@ -35,17 +35,8 @@ class BaseField(object):
         return value
 
     def __set__(self, instance, value):
-        """Descriptor for assigning a value to a field in a document. Do any 
-        necessary conversion between Python and MongoDB types.
+        """Descriptor for assigning a value to a field in a document.
         """
-        if value is not None:
-            try:
-                self.validate(value)
-            except (ValueError, AttributeError, AssertionError), e:
-                raise ValidationError('Invalid value for field of type "' +
-                                      self.__class__.__name__ + '"')
-        elif self.required:
-            raise ValidationError('Field "%s" is required' % self.name)
         instance._data[self.name] = value
 
     def to_python(self, value):
@@ -183,8 +174,6 @@ class BaseDocument(object):
             else:
                 # Use default value if present
                 value = getattr(self, attr_name, None)
-                if value is None and attr_value.required:
-                    raise ValidationError('Field "%s" is required' % attr_name)
                 setattr(self, attr_name, value)
 
     @classmethod

mongoengine/document.py

@@ -1,4 +1,5 @@
-from base import DocumentMetaclass, TopLevelDocumentMetaclass, BaseDocument
+from base import (DocumentMetaclass, TopLevelDocumentMetaclass, BaseDocument,
+                  ValidationError)
 from connection import _get_db
 
 
@@ -44,6 +45,7 @@ class Document(BaseDocument):
         document already exists, it will be updated, otherwise it will be
         created.
         """
+        self.validate()
         object_id = self.__class__.objects._collection.save(self.to_mongo())
         self.id = self._fields['id'].to_python(object_id)
 
@@ -54,6 +56,25 @@ class Document(BaseDocument):
         object_id = self._fields['id'].to_mongo(self.id)
         self.__class__.objects(id=object_id).delete()
 
+    def validate(self):
+        """Ensure that all fields' values are valid and that required fields
+        are present.
+        """
+        # Get a list of tuples of field names and their current values
+        fields = [(field, getattr(self, name)) 
+                  for name, field in self._fields.items()]
+
+        # Ensure that each field is matched to a valid value
+        for field, value in fields:
+            if value is not None:
+                try:
+                    field.validate(value)
+                except (ValueError, AttributeError, AssertionError), e:
+                    raise ValidationError('Invalid value for field of type "' +
+                                          field.__class__.__name__ + '"')
+            elif field.required:
+                raise ValidationError('Field "%s" is required' % field.name)
+
     @classmethod
     def drop_collection(cls):
         """Drops the entire collection associated with this