refs #13, enhance Alias usage

fix the issue that Alias methods like outjoin invoked Model, which
caused the loader couldn't find corresponding columns.

Author: wwwjfy

gino/crud.py

@@ -234,8 +234,8 @@ def __init__(self, model, *args, **kwargs):
 
     def __getattr__(self, item):
         rv = getattr(self.alias.columns, item,
-                     getattr(self.model, item,
-                             getattr(self.alias, item, DEFAULT)))
+                     getattr(self.alias, item,
+                             getattr(self.model, item, DEFAULT)))
         if rv is DEFAULT:
             raise AttributeError
         return rv

tests/test_loader.py

@@ -4,6 +4,7 @@
 import pytest
 from async_generator import yield_, async_generator
 
+from gino.loader import AliasLoader
 from .models import db, User, Team, Company
 
 pytestmark = pytest.mark.asyncio
@@ -144,6 +145,15 @@ def loader(row, context):
         assert u.team.parent.name == user.team.parent.name
 
 
+async def test_alias_loader_columns(user):
+    user_alias = User.alias()
+    base_query = user_alias.outerjoin(Team).select()
+
+    query = base_query.execution_options(loader=AliasLoader(user_alias, 'id'))
+    u = await query.gino.first()
+    assert u.id is not None
+
+
 async def test_adjacency_list_query_builder(user):
     group = Team.alias()
     u = await User.load(team=Team.load(parent=group.on(