fix: add QR token state lock primitive

tests/unit/test_pronote_auth_state.py

@@ -17,10 +17,12 @@ from __future__ import annotations
 import json
 import logging
 import os
+from fcntl import LOCK_EX, LOCK_NB, LOCK_UN, flock
 from pathlib import Path
 
 import pytest
 
+from pronote_sync.errors import PronoteAuthStateLockError
 from pronote_sync.sources.pronote.auth_state import PronoteAuthState
 
 
@@ -206,3 +208,76 @@ def test_no_credentials_in_logs(tmp_path: Path, caplog: pytest.LogCaptureFixture
     assert "SENTINEL_USER_ZZZ" not in caplog.text
     assert "SENTINEL_PASSWORD_ZZZ" not in caplog.text
     assert "SENTINEL_UUID_ZZZ" not in caplog.text
+
+
+def test_lock_rejects_concurrent_access_with_a_redacted_dedicated_error(tmp_path: Path) -> None:
+    """Vérifie qu'un verrou concurrent échoue immédiatement sans fuite interne.
+
+    :param tmp_path: Fixture pytest pour un répertoire temporaire.
+    :return: None
+    """
+    state_file = tmp_path / ".pronote_auth_state.json"
+    state = PronoteAuthState(state_file)
+    competing_state = PronoteAuthState(state_file)
+
+    with state.lock():
+        assert state_file.with_name(f"{state_file.name}.lock").exists()
+        with pytest.raises(PronoteAuthStateLockError) as exc_info:
+            with competing_state.lock():
+                pass
+
+    assert "BlockingIOError" not in str(exc_info.value)
+    assert exc_info.value.__cause__ is None
+    assert exc_info.value.__context__ is None
+
+
+def test_lock_open_failure_does_not_log_sensitive_lock_path(
+    tmp_path: Path, caplog: pytest.LogCaptureFixture, monkeypatch: pytest.MonkeyPatch
+) -> None:
+    """Vérifie qu'un échec d'ouverture du verrou ne divulgue pas son chemin.
+
+    :param tmp_path: Fixture pytest pour un répertoire temporaire.
+    :param caplog: Fixture pytest pour capturer les logs.
+    :param monkeypatch: Fixture pytest pour remplacer l'ouverture du verrou.
+    :return: None
+    """
+    sentinel_path = "/SENTINEL_LOCK_PATH_ZZZ/.pronote_auth_state.json.lock"
+
+    def raise_lock_open_error(*args: object, **kwargs: object) -> int:
+        """Simule un refus d'ouverture portant un chemin sensible."""
+        del args, kwargs
+        raise OSError(13, "Permission denied", sentinel_path)
+
+    monkeypatch.setattr(os, "open", raise_lock_open_error)
+
+    with caplog.at_level(logging.ERROR):
+        with pytest.raises(PronoteAuthStateLockError) as exc_info:
+            with PronoteAuthState(tmp_path / ".pronote_auth_state.json").lock():
+                pass
+
+    assert "Impossible d'ouvrir le verrou d'état d'authentification Pronote" in caplog.text
+    assert "SENTINEL_LOCK_PATH_ZZZ" not in caplog.text
+    assert exc_info.value.__cause__ is None
+    assert exc_info.value.__context__ is None
+
+
+def test_lock_is_released_when_the_protected_operation_raises(tmp_path: Path) -> None:
+    """Vérifie que le verrou est libéré même si le bloc protégé échoue.
+
+    :param tmp_path: Fixture pytest pour un répertoire temporaire.
+    :return: None
+    """
+    state_file = tmp_path / ".pronote_auth_state.json"
+    lock_file = state_file.with_name(f"{state_file.name}.lock")
+    state = PronoteAuthState(state_file)
+
+    with pytest.raises(RuntimeError, match="échec simulé"):
+        with state.lock():
+            raise RuntimeError("échec simulé")
+
+    descriptor = os.open(lock_file, os.O_RDWR)
+    try:
+        flock(descriptor, LOCK_EX | LOCK_NB)
+        flock(descriptor, LOCK_UN)
+    finally:
+        os.close(descriptor)