Use default MetaData() object instead of creating a new one

src/alchemical/core.py

@@ -31,9 +31,13 @@ class BaseModel:
 
     def __init_subclass__(cls, **kwargs):
         bind_key = getattr(cls, '__bind_key__', None)
-        if bind_key not in cls.__metadatas__:
-            cls.__metadatas__[bind_key] = MetaData()
-        cls.metadata = cls.__metadatas__[bind_key]
+        if bind_key is not None:
+            if bind_key not in cls.__metadatas__:
+                cls.__metadatas__[bind_key] = MetaData()
+            cls.metadata = cls.__metadatas__[bind_key]
+        elif None not in cls.__metadatas__ and \
+                getattr(cls, 'metadata', None) is not None:
+            cls.__metadatas__[None] = cls.metadata
         super().__init_subclass__(**kwargs)
 
     @classmethod

tests/test_aio.py

@@ -16,6 +16,7 @@ def wrapper(*args, **kwargs):
 
 class TestAio(unittest.TestCase):
     def setUp(self):
+        Model.metadata.clear()
         Model.__metadatas__.clear()
         clear_mappers()
 
@@ -29,6 +30,7 @@ class User(db.Model):
             name: Mapped[str]
 
         await db.create_all()
+        assert db.metadatas[None] == db.Model.metadata
         assert db.metadatas[None] == User.metadata
 
         async with db.begin() as session:

tests/test_core.py

@@ -14,6 +14,7 @@ def create_alchemical(self, url=None, binds=None):
         else:
             db = Alchemical()
             db.initialize(url, binds=binds)
+        db.Model.metadata.clear()
         db.Model.__metadatas__.clear()
         clear_mappers()
         return db
@@ -27,6 +28,7 @@ class User(db.Model):
             name: Mapped[str]
 
         db.create_all()
+        assert db.metadatas[None] == db.Model.metadata
         assert db.metadatas[None] == User.metadata
 
         with db.begin() as session:

tests/test_flask.py

@@ -8,6 +8,7 @@
 
 class TestFlask(unittest.TestCase):
     def setUp(self):
+        Model.metadata.clear()
         Model.__metadatas__.clear()
         clear_mappers()