[mypy] Enforcing typing for superset.migrations (#9583)

Co-authored-by: John Bodley <john.bodley@airbnb.com>

setup.cfg

@@ -53,7 +53,7 @@ order_by_type = false
 ignore_missing_imports = true
 no_implicit_optional = true
 
-[mypy-superset.bin.*,superset.charts.*,superset.datasets.*,superset.dashboards.*,superset.commands.*,superset.common.*,superset.dao.*,superset.db_engine_specs.*,superset.db_engines.*,superset.examples.*]
+[mypy-superset.bin.*,superset.charts.*,superset.datasets.*,superset.dashboards.*,superset.commands.*,superset.common.*,superset.dao.*,superset.db_engine_specs.*,superset.db_engines.*,superset.examples.*,superset.migrations.*]
 check_untyped_defs = true
 disallow_untyped_calls = true
 disallow_untyped_defs = true

superset/migrations/env.py

@@ -16,8 +16,11 @@
 # under the License.
 import logging
 from logging.config import fileConfig
+from typing import List
 
 from alembic import context
+from alembic.operations.ops import MigrationScript
+from alembic.runtime.migration import MigrationContext
 from flask import current_app
 from flask_appbuilder import Base
 from sqlalchemy import engine_from_config, pool
@@ -41,7 +44,7 @@
 # ... etc.
 
 
-def run_migrations_offline():
+def run_migrations_offline() -> None:
     """Run migrations in 'offline' mode.
 
     This configures the context with just a URL
@@ -60,7 +63,7 @@ def run_migrations_offline():
         context.run_migrations()
 
 
-def run_migrations_online():
+def run_migrations_online() -> None:
     """Run migrations in 'online' mode.
 
     In this scenario we need to create an Engine
@@ -71,9 +74,9 @@ def run_migrations_online():
     # this callback is used to prevent an auto-migration from being generated
     # when there are no changes to the schema
     # reference: https://alembic.sqlalchemy.org/en/latest/cookbook.html
-    def process_revision_directives(
-        context, revision, directives
-    ):  # pylint: disable=redefined-outer-name, unused-argument
+    def process_revision_directives(  # pylint: disable=redefined-outer-name, unused-argument
+        context: MigrationContext, revision: str, directives: List[MigrationScript]
+    ) -> None:
         if getattr(config.cmd_opts, "autogenerate", False):
             script = directives[0]
             if script.upgrade_ops.is_empty():