Reject duplicate module migration revisions

tests/test_database_migrations.py

@@ -1,11 +1,13 @@
 from __future__ import annotations
 
 import logging
+import os
 import tempfile
 import unittest
 from pathlib import Path
 
 from alembic import command
+from alembic.config import Config
 from alembic.runtime.migration import MigrationContext
 from alembic.script import ScriptDirectory
 from sqlalchemy import create_engine, inspect, text
@@ -16,6 +18,7 @@ from govoplan_core.db.migrations import (
     migrate_database,
     reconcile_change_sequence_retention_floor_drift,
     reconcile_namespace_table_drift,
+    validate_unique_migration_revisions,
 )
 
 
@@ -40,6 +43,25 @@ def database_migration_heads(connection) -> set[str]:
 
 
 class DatabaseMigrationTests(unittest.TestCase):
+    def test_duplicate_module_revision_ids_are_rejected_with_file_provenance(self) -> None:
+        with tempfile.TemporaryDirectory(prefix="govoplan-duplicate-revision-test-") as directory:
+            root = Path(directory)
+            first = root / "first"
+            second = root / "second"
+            first.mkdir()
+            second.mkdir()
+            (first / "first.py").write_text('revision = "duplicate123"\n', encoding="utf-8")
+            (second / "second.py").write_text('revision: str = "duplicate123"\n', encoding="utf-8")
+            config = Config()
+            config.set_main_option("version_locations", os.pathsep.join((str(first), str(second))))
+
+            with self.assertRaisesRegex(ValueError, "duplicate123") as raised:
+                validate_unique_migration_revisions(config)
+
+            message = str(raised.exception)
+            self.assertIn("first.py", message)
+            self.assertIn("second.py", message)
+
     def test_migration_logging_keeps_application_loggers_enabled(self) -> None:
         logger = logging.getLogger("govoplan.request")
         previous_disabled = logger.disabled