Decompose migration operations into individual sql functions

Author: jleclanche

postgres_composite_types/operations.py

@@ -5,6 +5,26 @@
 __all__ = ["BaseOperation"]
 
 
+def sql_field_definition(field_name, field, schema_editor):
+    quoted_name = schema_editor.quote_name(field_name)
+    db_type = field.db_type(schema_editor.connection)
+    return f"{quoted_name} {db_type}"
+
+
+def sql_create_type(type_name, fields, schema_editor):
+    fields_list = ", ".join(
+        sql_field_definition(field_name, field, schema_editor)
+        for field_name, field in fields
+    )
+    quoted_name = schema_editor.quote_name(type_name)
+    return f"CREATE TYPE {quoted_name} AS ({fields_list})"
+
+
+def sql_drop_type(type_name, schema_editor):
+    quoted_name = schema_editor.quote_name(type_name)
+    return f"DROP TYPE {quoted_name}"
+
+
 class BaseOperation(Operation):
     """Base class for the DB operation that relates to this type."""
 
@@ -18,20 +38,13 @@ def describe(self):
         return f"Creates type {self.Meta.db_type}"
 
     def database_forwards(self, app_label, schema_editor, from_state, to_state):
-        connection = schema_editor.connection
-        fields = ", ".join(
-            f"{schema_editor.quote_name(name)} {field.db_type(connection)}"
-            for name, field in self.Meta.fields
+        schema_editor.execute(
+            sql_create_type(self.Meta.db_type, self.Meta.fields, schema_editor)
+        )
+        self.Meta.model.register_composite(schema_editor.connection)
+        composite_type_created.send(
+            self.Meta.model, connection=schema_editor.connection
         )
-
-        type_name = schema_editor.quote_name(self.Meta.db_type)
-
-        schema_editor.execute(f"CREATE TYPE {type_name} AS ({fields})")
-
-        self.Meta.model.register_composite(connection)
-
-        composite_type_created.send(self.Meta.model, connection=connection)
 
     def database_backwards(self, app_label, schema_editor, from_state, to_state):
-        type_name = schema_editor.quote_name(self.Meta.db_type)
-        schema_editor.execute(f"DROP TYPE {type_name}")
+        return sql_drop_type(self.Meta.db_type, schema_editor=schema_editor)