Files
hermes-agent/tests/hermes_cli/test_atomic_json_write.py
teknium1 4157494d2f fix(utils): atomic_json_write escapes lone surrogates instead of raising UnicodeEncodeError
The canonical writer defaults to ensure_ascii=False, but ~10 of the sites
repointed onto it (terminal breadcrumbs, shell-hook allowlist, active
sessions, debug pending, model-catalog cache, the credential writers)
previously used json's ensure_ascii=True default. A surrogate-escaped str
(os.fsdecode of a non-UTF-8 cwd/argv) that json used to persist as \udcff
now made the utf-8 text handle raise UnicodeEncodeError - a ValueError that
the callers' `except OSError` never catches, so breadcrumbs silently stopped
writing and the other sites leaked a new error type.

Fix at the canonical: serialize to a str first (so nothing lands in the
temp file on failure), and on UnicodeEncodeError retry the dump with
ensure_ascii=True. That escape round-trips - json.loads returns the same
str with the lone surrogate - whereas encoding with surrogateescape emits a
raw 0xFF byte the reader's utf-8 decode rejects. The happy path is
unchanged: normal content keeps its raw UTF-8 bytes on disk.
2026-09-13 05:07:11 -07:00

86 lines
2.6 KiB
Python

"""Tests for utils.atomic_json_write — crash-safe JSON file writes."""
import json
import os
from pathlib import Path
from unittest.mock import patch
import pytest
from utils import atomic_json_write
class TestAtomicJsonWrite:
"""Core atomic write behavior."""
def test_cleans_up_temp_file_on_baseexception(self, tmp_path):
class SimulatedAbort(BaseException):
pass
target = tmp_path / "data.json"
original = {"preserved": True}
target.write_text(json.dumps(original), encoding="utf-8")
with patch("utils.json.dumps", side_effect=SimulatedAbort):
with pytest.raises(SimulatedAbort):
atomic_json_write(target, {"new": True})
tmp_files = [f for f in tmp_path.iterdir() if ".tmp" in f.name]
assert len(tmp_files) == 0
assert json.loads(target.read_text(encoding="utf-8")) == original
def test_mode_does_not_crash_without_fchmod(self, tmp_path):
"""Regression: os.fchmod is Unix-only and absent on Windows. Passing a
mode must not raise AttributeError when fchmod is unavailable.
Simulates the Windows os module by removing fchmod from the namespace.
Previously this crashed in `hermes memory setup` while saving the
Hindsight config with mode=0o600 (GitHub: Windows setup traceback).
"""
import utils
target = tmp_path / "secret.json"
no_fchmod = {k: getattr(os, k) for k in dir(os) if k != "fchmod"}
fake_os = type("FakeOs", (), no_fchmod)
assert not hasattr(fake_os, "fchmod")
with patch.object(utils, "os", fake_os):
atomic_json_write(target, {"api_key": "secret"}, mode=0o600)
assert json.loads(target.read_text(encoding="utf-8")) == {"api_key": "secret"}
def test_concurrent_writes_dont_corrupt(self, tmp_path):
"""Multiple rapid writes should each produce valid JSON."""
import threading
target = tmp_path / "concurrent.json"
errors = []
def writer(n):
try:
atomic_json_write(target, {"writer": n, "data": list(range(100))})
except Exception as e:
errors.append(e)
threads = [threading.Thread(target=writer, args=(i,)) for i in range(10)]
for t in threads:
t.start()
for t in threads:
t.join()
assert not errors
# File should contain valid JSON from one of the writers
result = json.loads(target.read_text())
assert "writer" in result
assert len(result["data"]) == 100