From 55d7eb3d4593f9c24f6de01b2ca6deb7a83ea588 Mon Sep 17 00:00:00 2001
From: Anna Schumaker <Anna@NoWheyCreamery.com>
Date: Thu, 4 May 2023 10:44:48 -0400
Subject: [PATCH] db: Raise an exception if the user_version is too new

Future proof. If we update the database schema, then we'll bump the
user_version field. If the user then tries to open the new database with
an old Emmental version then there could be a lot of issues. Let's
detect this and raise an error with a description of the problem.

Signed-off-by: Anna Schumaker <Anna@NoWheyCreamery.com>
---
 emmental/db/__init__.py | 16 +++++++++++-----
 tests/db/test_db.py     |  9 +++++++++
 2 files changed, 20 insertions(+), 5 deletions(-)

diff --git a/emmental/db/__init__.py b/emmental/db/__init__.py
index 1a98676..f7b8b02 100644
--- a/emmental/db/__init__.py
+++ b/emmental/db/__init__.py
@@ -29,11 +29,7 @@ class Connection(connection.Connection):
     def __init__(self):
         """Initialize a sqlite connection."""
         super().__init__()
-
-        match self("PRAGMA user_version").fetchone()["user_version"]:
-            case 0:
-                with open(SQL_SCRIPT) as f:
-                    self._sql.executescript(f.read())
+        self.__check_version()
 
         self.settings = settings.Table(self)
         self.playlists = playlists.Table(self)
@@ -47,6 +43,16 @@ class Connection(connection.Connection):
 
         self.tracks = tracks.Table(self)
 
+    def __check_version(self) -> None:
+        user_version = self("PRAGMA user_version").fetchone()["user_version"]
+        match user_version:
+            case 0:
+                with open(SQL_SCRIPT) as f:
+                    self._sql.executescript(f.read())
+            case 1: pass
+            case _:
+                raise Exception(f"Unsupported data version: {user_version}")
+
     def close(self) -> None:
         """Close the database connection."""
         self.settings.stop()
diff --git a/tests/db/test_db.py b/tests/db/test_db.py
index 716c023..3203cd5 100644
--- a/tests/db/test_db.py
+++ b/tests/db/test_db.py
@@ -23,6 +23,15 @@ class TestConnection(tests.util.TestCase):
         cur = self.sql("PRAGMA user_version")
         self.assertEqual(cur.fetchone()["user_version"], 1)
 
+    def test_version_too_new(self):
+        """Test failing when the database version is too new."""
+        self.sql._Connection__check_version()
+
+        self.sql("PRAGMA user_version = 2")
+        with self.assertRaises(Exception) as e:
+            self.sql._Connection__check_version()
+        self.assertEqual(str(e.exception), "Unsupported data version: 2")
+
     def test_close(self):
         """Check closing the connection."""
         self.sql.settings.queue.running = True