Harden backup JSON parsing and fix queue display

handlers/backup.py

@@ -30,6 +30,17 @@ async def _unit_status(unit: str, props: list[str]) -> dict[str, str]:
     return _parse_systemctl_kv(out)
 
 
+def _load_json(raw: str, label: str) -> tuple[bool, object | None, str]:
+    if not raw or not raw.strip():
+        return False, None, f"? {label} returned empty output"
+    try:
+        return True, json.loads(raw), ""
+    except json.JSONDecodeError:
+        preview = raw.strip().splitlines()
+        head = preview[0] if preview else "invalid output"
+        return False, None, f"? {label} invalid JSON: {head}"
+
+
 async def send_backup_jobs_status(msg: Message):
     services = [
         ("backup-auto", "backup-auto.timer"),
@@ -78,7 +89,11 @@ async def cmd_repo_stats(msg: Message):
         await msg.answer(raw1, reply_markup=backup_kb)
         return
 
-    restore = json.loads(raw1)
+    ok, restore, err = _load_json(raw1, "restic stats")
+    if not ok:
+        await msg.answer(err, reply_markup=backup_kb)
+        return
+
 
     # --- raw-data stats ---
     rc2, raw2 = await run_cmd(
@@ -90,7 +105,11 @@ async def cmd_repo_stats(msg: Message):
         await msg.answer(raw2, reply_markup=backup_kb)
         return
 
-    raw = json.loads(raw2)
+    ok, raw, err = _load_json(raw2, "restic stats raw-data")
+    if not ok:
+        await msg.answer(err, reply_markup=backup_kb)
+        return
+
 
     # --- snapshots count ---
     rc3, raw_snaps = await run_cmd(
@@ -98,7 +117,14 @@ async def cmd_repo_stats(msg: Message):
         use_restic_env=True,
         timeout=20
     )
-    snaps = len(json.loads(raw_snaps)) if rc3 == 0 else "n/a"
+    if rc3 != 0:
+        snaps = "n/a"
+    else:
+        ok, snap_data, err = _load_json(raw_snaps, "restic snapshots")
+        if ok and isinstance(snap_data, list):
+            snaps = len(snap_data)
+        else:
+            snaps = "n/a"
 
     msg_text = (
         "📦 **Repository stats**\n\n"
@@ -124,7 +150,10 @@ async def cmd_backup_status(msg: Message):
             await msg.answer(raw, reply_markup=backup_kb)
             return
 
-        snaps = json.loads(raw)
+        ok, snaps, err = _load_json(raw, "restic snapshots")
+        if not ok or not isinstance(snaps, list):
+            await msg.answer(err, reply_markup=backup_kb)
+            return
         if not snaps:
             await msg.answer("📦 Snapshots: none", reply_markup=backup_kb)
             return
@@ -193,7 +222,10 @@ async def cmd_last_snapshot(msg: Message):
             await msg.answer(raw, reply_markup=backup_kb)
             return
 
-        snaps = json.loads(raw)
+        ok, snaps, err = _load_json(raw, "restic snapshots")
+        if not ok or not isinstance(snaps, list):
+            await msg.answer(err, reply_markup=backup_kb)
+            return
         if not snaps:
             await msg.answer("📦 Snapshots: none", reply_markup=backup_kb)
             return
@@ -212,7 +244,10 @@ async def cmd_last_snapshot(msg: Message):
             await msg.answer(raw2, reply_markup=backup_kb)
             return
 
-        stats = json.loads(raw2)
+        ok, stats, err = _load_json(raw2, f"restic stats {short_id}")
+        if not ok or not isinstance(stats, dict):
+            await msg.answer(err, reply_markup=backup_kb)
+            return
 
         msg_text = (
             "📦 **Last snapshot**\n\n"