Fix drop model in the downgrade. (#132)

Author: long2ice

CHANGELOG.md

@@ -6,6 +6,7 @@
 
 - Fix tortoise connections not being closed properly. (#120)
 - Fix bug for field change. (#119)
+- Fix drop model in the downgrade. (#132)
 
 ### 0.5.0
 

aerich/migrate.py

@@ -169,7 +169,11 @@ def diff_models(cls, old_models: Dict[str, dict], new_models: Dict[str, dict], u
             model = cls._get_model(new_model_describe.get("name").split(".")[1])
 
             if new_model_str not in old_models.keys():
-                cls._add_operator(cls.add_model(model), upgrade)
+                if upgrade:
+                    cls._add_operator(cls.add_model(model), upgrade)
+                else:
+                    # we can't find origin model when downgrade, so skip
+                    pass
             else:
                 old_model_describe = old_models.get(new_model_str)
 

poetry.lock

@@ -66,3 +66,7 @@ class Config(Model):
     value = fields.JSONField()
     status: Status = fields.IntEnumField(Status)
     user = fields.ForeignKeyField("models.User", description="User")
+
+
+class NewModel(Model):
+    name = fields.CharField(max_length=50)