Fix post-migrate call. Replace with manual migrations

Author: zkayyali812

ansible_base/feature_flags/apps.py

@@ -11,7 +11,4 @@ class FeatureFlagsConfig(AppConfig):
     verbose_name = 'Feature Flags'
 
     def ready(self):
-        try:
-            create_initial_data()
-        except Exception:
-            post_migrate.connect(create_initial_data, sender=self)
+        post_migrate.connect(create_initial_data, sender=self)

ansible_base/feature_flags/migrations/0001_initial.py

@@ -1,4 +1,5 @@
 # Generated by Django 4.2.21 on 2025-06-17 20:08
+# FileHash: df8a46833e96d189abbfb07f557975091a80adbe3637e365d93ff7acb7fb3343
 
 import ansible_base.feature_flags.models.aap_flag
 from django.conf import settings

ansible_base/feature_flags/migrations/example_migration

@@ -0,0 +1,21 @@
+### INSTRUCTIONS ###
+# If updating the feature_flags.yaml, create a new migration file by copying this one.
+# 1. Name the file XXXX_manual_YYYYMMDD.py. For example 0002_manual_20250808.py
+# 1. Uncomment the migration below, by uncommenting everything below the FileHash
+# 2. Update the dependency to point to the last dependency
+# 3. Set the FileHash
+###
+
+# FileHash: <FileHash>
+
+# from django.db import migrations
+
+
+# class Migration(migrations.Migration):
+
+#     dependencies = [
+#         ('dab_feature_flags', '0001_initial'),
+#     ]
+
+#     operations = [
+#     ]

docs/apps/feature_flags.md

@@ -48,9 +48,9 @@ urlpatterns = [
 ]
 ```
 
-## Adding Feature Flags
+## Adding/updating/removing feature flags
 
-To add a feature flag to the platform, specify it in the following [file](../../ansible_base/feature_flags/definitions/feature_flags.yaml)
+To add/update/remove a feature flag to the platform, ensure its configuration is specified correctly it in the following [file](../../ansible_base/feature_flags/definitions/feature_flags.yaml)
 
 An example flag could resemble -
 
@@ -73,3 +73,11 @@ Validate this file against the json schema by running `check-jsonschema` -
 pip install check-jsonschema
 check-jsonschema --schemafile ansible_base/feature_flags/definitions/schema.json ansible_base/feature_flags/definitions/feature_flags.yaml
 ```
+
+After adding/updating/removing a feature flag, make a manual migration. This can be done by -
+
+1. Copying this [example-migration](../../ansible_base/feature_flags/migrations/example_migration).
+2. Name the file XXXX_manual_YYYYMMDD.py. For example 0002_manual_20250808.py
+3. Uncomment the migration, by uncommenting everything below the FileHash
+4. Update the dependency in the migration to point to the previous migration
+5. Set the **FileHash** in the migration file

test_app/tests/feature_flags/migrations/test_migrations.py

@@ -0,0 +1,82 @@
+import hashlib
+import os
+
+from django.conf import settings
+from django.test import TestCase
+
+
+class FileHashTest(TestCase):
+    FILE_TO_CHECK_PATH = os.path.join(settings.BASE_DIR, 'ansible_base', 'feature_flags', 'definitions', 'feature_flags.yaml')
+    HASH_ALGORITHM = 'sha256'
+    HASH_COMMENT_PREFIX = '# FileHash:'
+
+    def _get_last_migration_file(self):
+        """
+        Finds the path to the last migration file in the specified Django app.
+        """
+        migrations_dir = os.path.join(settings.BASE_DIR, 'ansible_base', 'feature_flags', 'migrations')
+        if not os.path.isdir(migrations_dir):
+            raise FileNotFoundError(f"Migrations directory not found for app: {self.APP_NAME}")
+
+        migration_files = sorted([
+            f for f in os.listdir(migrations_dir)
+            if f.endswith('.py') and f != '__init__.py'
+        ])
+
+        if not migration_files:
+            raise FileNotFoundError(f"No migration files found in {migrations_dir}")
+
+        return os.path.join(migrations_dir, migration_files[-1])
+
+    def _extract_hash_from_migration(self, migration_file_path):
+        """
+        Extracts the expected hash from a comment in the migration file.
+        Assumes the format: '# FileHash: <hash_value>'
+        """
+        with open(migration_file_path, 'r') as f:
+            for line in f:
+                if line.strip().startswith(self.HASH_COMMENT_PREFIX):
+                    return line.strip().replace(self.HASH_COMMENT_PREFIX, '').strip()
+        return None
+
+    def _calculate_file_hash(self, file_path):
+        """
+        Calculates the hash of the given file.
+        """
+        hash_func = getattr(hashlib, self.HASH_ALGORITHM, None)
+        if not hash_func:
+            raise ValueError(f"Unsupported hash algorithm: {self.HASH_ALGORITHM}")
+
+        hasher = hash_func()
+        with open(file_path, 'rb') as f:
+            for chunk in iter(lambda: f.read(4096), b""):
+                hasher.update(chunk)
+        return hasher.hexdigest()
+
+    def test_file_hash_matches_migration_comment(self):
+        """
+        Checks if the hash of a specified file matches the hash commented
+        in the last migration file.
+        """
+        # 1. Get the last migration file
+        try:
+            last_migration_file = self._get_last_migration_file()
+        except FileNotFoundError as e:
+            self.fail(f"Could not find last migration file: {e}")
+
+        # 2. Extract the expected hash from the migration file
+        expected_hash = self._extract_hash_from_migration(last_migration_file)
+        self.assertIsNotNone(expected_hash,
+                             f"No hash comment '{self.HASH_COMMENT_PREFIX}' found in {last_migration_file}")
+        self.assertTrue(expected_hash, "Extracted hash is empty.")
+
+        # 3. Calculate the hash of the target file
+        self.assertTrue(os.path.exists(self.FILE_TO_CHECK_PATH),
+                        f"File to check does not exist: {self.FILE_TO_CHECK_PATH}")
+        actual_hash = self._calculate_file_hash(self.FILE_TO_CHECK_PATH)
+
+        # 4. Compare the hashes
+        self.assertEqual(expected_hash, actual_hash,
+                         f"Hash mismatch for '{os.path.basename(self.FILE_TO_CHECK_PATH)}'. "
+                         f"Expected: {expected_hash}, Got: {actual_hash} "
+                         f"If the feature_flags.yaml file changed, generate a new no-op migration file, and correctly set the FileHash.")