added a test for setting a column as nullable via a MigrationManager

Author: dantownsend

tests/apps/migrations/auto/test_migration_manager.py

@@ -310,6 +310,36 @@ def test_alter_column_unique(self):
         response = self.run_sync("SELECT name FROM manager;")
         self.assertEqual(response, [{"name": "Dave"}, {"name": "Dave"}])
 
+    @postgres_only
+    def test_alter_column_set_null(self):
+        """
+        Test altering whether a column is nullable with MigrationManager.
+        """
+        manager = MigrationManager()
+
+        manager.alter_column(
+            table_class_name="Manager",
+            tablename="manager",
+            column_name="name",
+            params={"null": True},
+            old_params={"null": False},
+        )
+
+        asyncio.run(manager.run())
+        self.assertTrue(
+            self.get_postgres_is_nullable(
+                tablename="manager", column_name="name"
+            )
+        )
+
+        # Reverse
+        asyncio.run(manager.run_backwards())
+        self.assertFalse(
+            self.get_postgres_is_nullable(
+                tablename="manager", column_name="name"
+            )
+        )
+
     def _get_column_precision_and_scale(
         self, tablename="ticket", column_name="price"
     ):

tests/base.py

@@ -55,22 +55,46 @@ def table_exists(self, tablename: str) -> bool:
         _Table._meta.tablename = tablename
         return _Table.table_exists().run_sync()
 
-    def get_postgres_column_type_str(
+    ###########################################################################
+
+    # Postgres specific utils
+
+    def get_postgres_column_definition(
         self, tablename: str, column_name: str
-    ) -> str:
-        """
-        Fetches the column type as a string, from the database.
-        """
+    ) -> t.Dict[str, t.Any]:
         query = """
-            SELECT data_type FROM information_schema.columns
+            SELECT * FROM information_schema.columns
             WHERE table_name = '{tablename}'
             AND table_catalog = 'piccolo'
             AND column_name = '{column_name}'
         """.format(
             tablename=tablename, column_name=column_name
         )
         response = self.run_sync(query)
-        return response[0]["data_type"].upper()
+        return response[0]
+
+    def get_postgres_column_type_str(
+        self, tablename: str, column_name: str
+    ) -> str:
+        """
+        Fetches the column type as a string, from the database.
+        """
+        return self.get_postgres_column_definition(
+            tablename=tablename, column_name=column_name
+        )["data_type"].upper()
+
+    def get_postgres_is_nullable(self, tablename, column_name: str) -> bool:
+        """
+        Fetches whether the column is defined as nullable, from the database.
+        """
+        return (
+            self.get_postgres_column_definition(
+                tablename=tablename, column_name=column_name
+            )["is_nullable"].upper()
+            == "YES"
+        )
+
+    ###########################################################################
 
     def create_tables(self):
         if ENGINE.engine_type == "postgres":