Dirty workaround to prevent redefinition of SQLAlchemy ORM model classes

platypush/entities/_base.py

@@ -2,7 +2,7 @@ import inspect
 import pathlib
 import types
 from datetime import datetime
-from typing import Mapping, Type, Tuple, Any
+from typing import Dict, Mapping, Type, Tuple, Any
 
 import pkgutil
 from sqlalchemy import (
@@ -22,6 +22,7 @@ from platypush.message import JSONAble
 
 Base = declarative_base()
 entities_registry: Mapping[Type['Entity'], Mapping] = {}
+entity_types_registry: Dict[str, Type['Entity']] = {}
 
 
 class Entity(Base):
@@ -30,7 +31,6 @@ class Entity(Base):
     """
 
     __tablename__ = 'entity'
-    __table_args__ = {'extend_existing': True}
 
     id = Column(Integer, autoincrement=True, primary_key=True)
     external_id = Column(String, nullable=True)
@@ -54,6 +54,7 @@ class Entity(Base):
     __table_args__ = (
         Index('name_and_plugin_index', name, plugin),
         Index('name_type_and_plugin_index', name, type, plugin),
+        {'extend_existing': True},
     )
 
     __mapper_args__ = {

platypush/entities/devices.py

@@ -1,14 +1,22 @@
 from sqlalchemy import Column, Integer, Boolean, ForeignKey
 
-from ._base import Entity
+from ._base import Entity, entity_types_registry
 
 
+if not entity_types_registry.get('Device'):
+
     class Device(Entity):
         __tablename__ = 'device'
 
-    id = Column(Integer, ForeignKey(Entity.id, ondelete='CASCADE'), primary_key=True)
+        id = Column(
+            Integer, ForeignKey(Entity.id, ondelete='CASCADE'), primary_key=True
+        )
         reachable = Column(Boolean, default=True)
 
         __mapper_args__ = {
             'polymorphic_identity': __tablename__,
         }
+
+    entity_types_registry['Device'] = Device
+else:
+    Device = entity_types_registry['Device']

platypush/entities/lights.py

@@ -1,12 +1,16 @@
 from sqlalchemy import Column, Integer, String, ForeignKey, Boolean, Float
 
-from .devices import Device
+from .devices import Device, entity_types_registry
 
 
+if not entity_types_registry.get('Light'):
+
     class Light(Device):
         __tablename__ = 'light'
 
-    id = Column(Integer, ForeignKey(Device.id, ondelete='CASCADE'), primary_key=True)
+        id = Column(
+            Integer, ForeignKey(Device.id, ondelete='CASCADE'), primary_key=True
+        )
         on = Column(Boolean)
         brightness = Column(Float)
         saturation = Column(Float)
@@ -28,3 +32,7 @@ class Light(Device):
         __mapper_args__ = {
             'polymorphic_identity': __tablename__,
         }
+
+    entity_types_registry['Light'] = Light
+else:
+    Light = entity_types_registry['Light']

platypush/entities/switches.py

@@ -1,14 +1,22 @@
 from sqlalchemy import Column, Integer, ForeignKey, Boolean
 
-from .devices import Device
+from .devices import Device, entity_types_registry
 
 
+if not entity_types_registry.get('Switch'):
+
     class Switch(Device):
         __tablename__ = 'switch'
 
-    id = Column(Integer, ForeignKey(Device.id, ondelete='CASCADE'), primary_key=True)
+        id = Column(
+            Integer, ForeignKey(Device.id, ondelete='CASCADE'), primary_key=True
+        )
         state = Column(Boolean)
 
         __mapper_args__ = {
             'polymorphic_identity': __tablename__,
         }
+
+    entity_types_registry['Switch'] = Switch
+else:
+    Switch = entity_types_registry['Switch']