Fix rollback behavior (#19)

Co-authored-by: Nate Rubin <nrubin@element84.com>

Author: naterubin

src/dbami/db.py

@@ -538,7 +538,7 @@ async def migrate(
 
                 # build rollback chain
                 chain: list[Migration] = []
-                while next_migration and next_migration.id >= target:
+                while next_migration and next_migration.id > target:
                     if next_migration.down is None:
                         raise exceptions.MigrationError(
                             f"Cannot rollback from version {schema_version} "
@@ -556,7 +556,7 @@ async def migrate(
                         async with conn.transaction():
                             await self.run_sqlfile(migration.down, conn=conn)
                             await self._update_schema_version(
-                                migration.id,
+                                migration.id - 1,
                                 conn,
                             )
 

tests/conftest.py

@@ -35,10 +35,11 @@ def project(tmp_chdir: Path):
     migrations_dir.mkdir()
     migrations_dir.joinpath("00000_base.down.sql").touch()
     migrations_dir.joinpath("01_migration.up.sql").touch()
+    migrations_dir.joinpath("01_migration.down.sql").touch()
+    migrations_dir.joinpath("02_migration.up.sql").touch()
     db: DB = DB.new_project(tmp_chdir)
     db.new_migration("migration")
     db.new_migration("migration")
-    db.new_migration("migration")
     db.new_fixture("a_fixture")
     db.fixtures["a_fixture"].path.write_text("select current_database();")
     return db

tests/test_db.py

@@ -123,7 +123,7 @@ async def test_rollback(tmp_db, project):
 
 @pytest.mark.asyncio
 async def test_rollback_bad_file(tmp_db, project):
-    project.migrations[2].down.path.write_text("not valid sql")
+    project.migrations[3].down.path.write_text("not valid sql")
     await project.load_schema(database=tmp_db)
     with pytest.raises(asyncpg.PostgresSyntaxError):
         await project.migrate(target=2, database=tmp_db)