Merge pull request 'Make save operation transactional' (#3) from transaction_patch into main

Reviewed-on: #3

README.md

@@ -5,7 +5,7 @@
 # chguard
 
 <div align="center">
-  <img src="chguard.png" alt="chguard logo" width="256" />
+  <img src="https://git.sysmd.uk/guardutils/chguard/src/branch/main/chguard.png" alt="chguard logo" width="256" />
 </div>
 
 

chguard/cli.py

@@ -248,14 +248,19 @@ def main() -> None:
 
         root = normalize_root(args.save)
 
+        try:
+            with conn:  # start transaction
                 if state_exists(conn, args.name):
                     if not args.overwrite:
                         raise SystemExit(
                             f"State '{args.name}' already exists (use --overwrite)"
                         )
-            delete_state(conn, args.name)
+                    # if the new save fails, this delete_state step will also roll back
+                    delete_state(conn, args.name, commit=False)
 
-        state_id = create_state(conn, args.name, str(root), os.getuid())
+                state_id = create_state(
+                    conn, args.name, str(root), os.getuid(), commit=False
+                )
 
                 # Abort early if root-owned files exist and user is not root.
                 # This prevents creating snapshots that cannot be meaningfully restored.
@@ -281,10 +286,12 @@ def main() -> None:
                         ),
                     )
 
-        conn.commit()
             console.print(f"Saved state '{args.name}' for {root}")
             return
 
+        except SystemExit:
+            raise
+
     if args.restore:
         if not args.state:
             parser.error("STATE is required with --restore")

chguard/db.py

@@ -61,18 +61,27 @@ def state_exists(conn: sqlite3.Connection, name: str) -> bool:
 
 
 def create_state(
-    conn: sqlite3.Connection, name: str, root_path: str, created_by_uid: int
+    conn: sqlite3.Connection,
+    name: str,
+    root_path: str,
+    created_by_uid: int,
+    *,
+    commit: bool = True,
 ) -> int:
     cur = conn.execute(
         "INSERT INTO states (name, root_path, created_at, created_by_uid) VALUES (?, ?, ?, ?)",
         (name, root_path, utc_now_iso(), created_by_uid),
     )
+    if commit:
         conn.commit()
     return int(cur.lastrowid)
 
 
-def delete_state(conn: sqlite3.Connection, name: str) -> int:
+def delete_state(
+    conn: sqlite3.Connection, name: str, commit: bool = True
+) -> int:
     cur = conn.execute("DELETE FROM states WHERE name = ?", (name,))
+    if commit:
         conn.commit()
     return cur.rowcount
 

pyproject.toml

@@ -1,6 +1,6 @@
 [tool.poetry]
 name = "chguard"
-version = "0.2.1"
+version = "0.2.2"
 description = "Safety-first tool to snapshot and restore filesystem ownership and permissions."
 authors = ["Marco D'Aleo <marco@marcodaleo.com>"]
 license = "GPL-3.0-or-later"