fix #307, explicit error when bind is None

Author: wwwjfy

gino/api.py

@@ -7,6 +7,7 @@
 
 from .crud import CRUDModel
 from .declarative import declarative_base, declared_attr
+from .exceptions import UninitializedError
 from .schema import GinoSchemaVisitor, patch_schema
 from . import json_support
 
@@ -361,6 +362,9 @@ def bind(self):
         :class:`~sqlalchemy.engine.url.URL`).
 
         """
+        if self._bind is None:
+            return _PlaceHolder(
+                UninitializedError('Gino engine is not initialized.'))
         return self._bind
 
     # noinspection PyMethodOverriding,PyAttributeOutsideInit
@@ -483,3 +487,20 @@ def transaction(self, *args, **kwargs):
 
         """
         return self.bind.transaction(*args, **kwargs)
+
+
+class _PlaceHolder:
+    __slots__ = '_exception'
+
+    def __init__(self, exception):
+        self._exception = exception
+
+    def __getattribute__(self, item):
+        if item == '_exception':
+            return super().__getattribute__(item)
+        raise self._exception
+
+    def __setattr__(self, key, value):
+        if key == '_exception':
+            return super().__setattr__(key, value)
+        raise UninitializedError(self._exception)

gino/exceptions.py

@@ -4,3 +4,7 @@ class GinoException(Exception):
 
 class NoSuchRowError(GinoException):
     pass
+
+
+class UninitializedError(GinoException):
+    pass

tests/test_bind.py

@@ -1,5 +1,6 @@
 import random
 
+from gino.exceptions import UninitializedError
 import pytest
 
 from .models import db, PG_URL, User
@@ -30,8 +31,11 @@ async def test_unbind(asyncpg_pool):
     await test_create(None)
     await db.pop_bind().close()
     db.bind = None
-    with pytest.raises(AttributeError):
+    with pytest.raises(UninitializedError):
         await test_create(None)
+    # test proper exception when engine is not initialized
+    with pytest.raises(UninitializedError):
+        db.bind.first = lambda x: 1
 
 
 async def test_db_api(bind, random_name):

tests/test_engine.py

@@ -3,10 +3,11 @@
 from datetime import datetime
 
 import asyncpg
+from asyncpg.exceptions import InvalidCatalogNameError
+from gino import UninitializedError
 import pytest
-import sqlalchemy as sa
 from sqlalchemy.exc import ObjectNotExecutableError
-from asyncpg.exceptions import InvalidCatalogNameError
+import sqlalchemy as sa
 
 from .models import db, User, PG_URL, qsize
 
@@ -181,7 +182,8 @@ async def test_async_metadata():
     db_ = await gino.Gino(PG_URL)
     assert isinstance((await db_.scalar('select now()')), datetime)
     await db_.pop_bind().close()
-    assert db.bind is None
+    with pytest.raises(UninitializedError):
+        db.bind.first()
 
 
 # noinspection PyUnreachableCode

tests/test_iterate.py

@@ -1,3 +1,4 @@
+from gino import UninitializedError
 import pytest
 
 from .models import db, User
@@ -74,7 +75,7 @@ async def test_bind(bind, names):
 async def test_basic(engine, names):
     result = set()
     async with engine.transaction() as tx:
-        with pytest.raises(AttributeError, match='iterate'):
+        with pytest.raises(UninitializedError):
             await db.iterate(User.query)
         result = set()
         async for u in tx.connection.iterate(User.query):