fix: aerich migrate crashes without init-db & aerich init-db should create folder after validating app (#443)

* fix: aerich init-db should create folder after get_app_connection

* fix: migrate without init-db will raise error

* aerich init-db should create folder after validating app

* fix: catch empty old model exception and raise with a tip.

Author: hail-pas

aerich/__init__.py

@@ -256,6 +256,10 @@ async def migrate(self, name: str = "update", empty: bool = False) -> str:
     async def init_db(self, safe: bool) -> None:
         location = self.location
         app = self.app
+
+        await Tortoise.init(config=self.tortoise_config)
+        connection = get_app_connection(self.tortoise_config, app)
+
         dirname = Path(location, app)
         if not dirname.exists():
             dirname.mkdir(parents=True)
@@ -264,8 +268,6 @@ async def init_db(self, safe: bool) -> None:
             for unexpected_file in dirname.glob("*"):
                 raise FileExistsError(str(unexpected_file))
 
-        await Tortoise.init(config=self.tortoise_config)
-        connection = get_app_connection(self.tortoise_config, app)
         await generate_schema_for_client(connection, safe)
 
         schema = get_schema_sql(connection, safe)

aerich/migrate.py

@@ -405,7 +405,13 @@ def diff_models(
         :return:
         """
         _aerich = f"{cls.app}.{cls._aerich}"
-        old_models.pop(_aerich, None)
+        try:
+            old_models.pop(_aerich, None)
+        except AttributeError:
+            # Invalid use when app migration directory exists but aerich table not exist
+            raise click.UsageError(
+                "You may need to run `aerich init-db` first to initialize the database."
+            )
         new_models.pop(_aerich, None)
         models_with_rename_field: set[str] = set()  # models that trigger the click.prompt