fix #717, return empty objects instead of None

For queries that request for selected columns and all the returned
results are NULL, still construct the objects with all values None.

Author: wwwjfy

mysql_tests/test_loader.py

@@ -368,23 +368,12 @@ async def test_tuple_loader_279(user):
 
 
 async def test_none_as_none_281(user):
-    import gino
+    query = Team.outerjoin(User).select()
+    loader = Team, User
+    assert any(row[1] is None for row in await query.gino.load(loader).all())
 
-    if gino.__version__ < "0.9":
-        query = Team.outerjoin(User).select()
-        loader = Team, User.none_as_none()
-        assert any(row[1] is None for row in await query.gino.load(loader).all())
-
-        loader = Team.distinct(Team.id).load(add_member=User.none_as_none())
-        assert any(not team.members for team in await query.gino.load(loader).all())
-
-    if gino.__version__ >= "0.8.0":
-        query = Team.outerjoin(User).select()
-        loader = Team, User
-        assert any(row[1] is None for row in await query.gino.load(loader).all())
-
-        loader = Team.distinct(Team.id).load(add_member=User)
-        assert any(not team.members for team in await query.gino.load(loader).all())
+    loader = Team.distinct(Team.id).load(add_member=User)
+    assert any(not team.members for team in await query.gino.load(loader).all())
 
 
 async def test_model_in_query(user):
@@ -400,3 +389,10 @@ async def test_model_in_query(user):
     assert users[0] != user
     assert users[0].id == user.id
     assert users[0].nickname == user.nickname
+
+
+async def test_empty_model(user):
+    u = await User.query.with_only_columns([User.realname]).gino.first()
+    assert u is not None
+    assert u.id is None
+    assert u.realname is None

src/gino/loader.py

@@ -212,9 +212,9 @@ def __init__(self, model, *columns, **extras):
         self.extras = dict((key, self.get(value)) for key, value in extras.items())
         self.on_clause = None
 
-    def _do_load(self, row):
+    def _do_load(self, row, none_as_none):
         values = dict((c.name, row[c]) for c in self.columns if c in row)
-        if all((v is None) for v in values.values()):
+        if none_as_none and all((v is None) for v in values.values()):
             return None
         rv = self.model()
         for c in self.columns:
@@ -241,17 +241,18 @@ def do_load(self, row, context):
             key = tuple(row[col] for col in self._distinct)
             rv = ctx.get(key, _none)
             if rv is _none:
-                rv = self._do_load(row)
+                rv = self._do_load(row, context.get('none_as_none', False))
                 ctx[key] = rv
             else:
                 distinct = False
         else:
-            rv = self._do_load(row)
+            rv = self._do_load(row, context.get('none_as_none', False))
 
         if rv is None:
             return None, None
         else:
             for key, value in self.extras.items():
+                context.setdefault('none_as_none', True)
                 value, distinct_ = value.do_load(row, context)
                 if distinct_ is None:
                     continue

tests/test_loader.py

@@ -368,23 +368,12 @@ async def test_tuple_loader_279(user):
 
 
 async def test_none_as_none_281(user):
-    import gino
+    query = Team.outerjoin(User).select()
+    loader = Team, User
+    assert any(row[1] is None for row in await query.gino.load(loader).all())
 
-    if gino.__version__ < "0.9":
-        query = Team.outerjoin(User).select()
-        loader = Team, User.none_as_none()
-        assert any(row[1] is None for row in await query.gino.load(loader).all())
-
-        loader = Team.distinct(Team.id).load(add_member=User.none_as_none())
-        assert any(not team.members for team in await query.gino.load(loader).all())
-
-    if gino.__version__ >= "0.8.0":
-        query = Team.outerjoin(User).select()
-        loader = Team, User
-        assert any(row[1] is None for row in await query.gino.load(loader).all())
-
-        loader = Team.distinct(Team.id).load(add_member=User)
-        assert any(not team.members for team in await query.gino.load(loader).all())
+    loader = Team.distinct(Team.id).load(add_member=User)
+    assert any(not team.members for team in await query.gino.load(loader).all())
 
 
 async def test_model_in_query(user):
@@ -400,3 +389,10 @@ async def test_model_in_query(user):
     assert users[0] != user
     assert users[0].id == user.id
     assert users[0].nickname == user.nickname
+
+
+async def test_empty_model(user):
+    u = await User.query.with_only_columns([User.realname]).gino.first()
+    assert u is not None
+    assert u.id is None
+    assert u.realname is None