Refactor sql_analyser into multiple classes for simpler extension in the future

django_migration_linter/sql_analyser/mysql.py

@@ -0,0 +1,29 @@
+# Copyright 2019 3YOURMIND GmbH
+
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+
+# http://www.apache.org/licenses/LICENSE-2.0
+
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+import re
+
+from .base import BaseAnalyser
+
+
+class MySqlAnalyser(BaseAnalyser):
+    migration_tests = [
+        {
+            "code": "ALTER_COLUMN",
+            "fn": lambda sql, **kw: re.search(
+                "ALTER TABLE .* MODIFY .* (?!NULL);?$", sql
+            ),
+            "mode": "one_liner",
+        }
+    ]