Add internal classes and add type hints + mypy.

django_migration_linter/utils.py

@@ -1,9 +1,11 @@
+from __future__ import annotations
+
 import os
 from importlib import import_module
 
 
-def split_path(path):
-    decomposed_path = []
+def split_path(path: str) -> list[str]:
+    decomposed_path: list[str] = []
     while 1:
         head, tail = os.path.split(path)
         if head == path:  # sentinel for absolute paths
@@ -21,20 +23,21 @@ def split_path(path):
     return decomposed_path
 
 
-def split_migration_path(migration_path):
+def split_migration_path(migration_path: str) -> tuple[str, str]:
     from django.db.migrations.loader import MIGRATIONS_MODULE_NAME
 
     decomposed_path = split_path(migration_path)
     for i, p in enumerate(decomposed_path):
         if p == MIGRATIONS_MODULE_NAME:
             return decomposed_path[i - 1], os.path.splitext(decomposed_path[i + 1])[0]
+    return "", ""
 
 
-def clean_bytes_to_str(byte_input):
+def clean_bytes_to_str(byte_input: bytes) -> str:
     return byte_input.decode("utf-8").strip()
 
 
-def get_migration_abspath(app_label, migration_name):
+def get_migration_abspath(app_label: str, migration_name: str) -> str:
     from django.db.migrations.loader import MigrationLoader
 
     module_name, _ = MigrationLoader.migrations_module(app_label)
@@ -42,6 +45,9 @@ def get_migration_abspath(app_label, migration_name):
     migration_module = import_module(migration_path)
 
     migration_file = migration_module.__file__
+    if not migration_file:
+        raise ValueError("Migration file not found")
+
     if migration_file.endswith(".pyc"):
         migration_file = migration_file[:-1]
     return migration_file