fix: fall back to direct write when atomic state save hits EPERM on NFS

app/tests/test_state_store.py

@@ -4,6 +4,7 @@ import os
 import tempfile
 import unittest
 from datetime import datetime
+from unittest.mock import patch
 
 from state_store import AtomicJsonStore, from_json_compatible, to_json_compatible
 
@@ -21,6 +22,55 @@ class StateStoreTests(unittest.TestCase):
             self.assertEqual(payload["schema_version"], 2)
             self.assertEqual(payload["items"][0]["info"]["title"], "hello")
 
+    def test_save_falls_back_to_direct_write_when_mkstemp_fails(self):
+        with tempfile.TemporaryDirectory() as tmp:
+            path = os.path.join(tmp, "queue.json")
+            store = AtomicJsonStore(path, kind="persistent_queue:queue")
+
+            with self.assertLogs("state_store", level="WARNING") as logs:
+                with patch(
+                    "state_store.tempfile.mkstemp",
+                    side_effect=PermissionError(1, "Operation not permitted"),
+                ):
+                    store.save({"items": [{"key": "a"}]})
+
+            self.assertTrue(os.path.exists(path))
+            self.assertTrue(any(path in message for message in logs.output))
+            payload = store.load()
+            self.assertEqual(payload["items"], [{"key": "a"}])
+
+    def test_save_falls_back_to_direct_write_when_replace_fails(self):
+        with tempfile.TemporaryDirectory() as tmp:
+            path = os.path.join(tmp, "queue.json")
+            store = AtomicJsonStore(path, kind="persistent_queue:queue")
+
+            with patch(
+                "state_store.os.replace",
+                side_effect=PermissionError(1, "Operation not permitted"),
+            ):
+                store.save({"items": [{"key": "a"}]})
+
+            self.assertTrue(os.path.exists(path))
+            payload = store.load()
+            self.assertEqual(payload["items"], [{"key": "a"}])
+            self.assertEqual([], [name for name in os.listdir(tmp) if name.endswith(".tmp")])
+
+    def test_save_reraises_when_atomic_and_direct_write_fail(self):
+        with tempfile.TemporaryDirectory() as tmp:
+            path = os.path.join(tmp, "queue.json")
+            store = AtomicJsonStore(path, kind="persistent_queue:queue")
+
+            with patch(
+                "state_store.tempfile.mkstemp",
+                side_effect=PermissionError(1, "Operation not permitted"),
+            ):
+                with patch("builtins.open", side_effect=PermissionError(13, "Permission denied")):
+                    with self.assertRaises(PermissionError) as ctx:
+                        store.save({"items": [{"key": "a"}]})
+
+            self.assertEqual(ctx.exception.errno, 13)
+            self.assertFalse(os.path.exists(path))
+
     def test_invalid_file_is_quarantined(self):
         with tempfile.TemporaryDirectory() as tmp:
             path = os.path.join(tmp, "queue.json")