fix(music): honor umask when publishing lyric sidecars (#7065)

歌词临时文件在原子替换前使用与其他刮削文件一致的 0666 & ~UMASK 权限，避免 TXT、LRC 和 Lyricsfile 沿用临时文件的 0600 权限，导致不同 UID 的媒体服务器无法读取。

覆盖写入同样遵循部署权限；保留链接种源保护和失败时清理临时文件的行为。

验证：198 项相关 pytest 回归通过；变更文件 Pylint、Ruff ratchet、mypy ratchet、复杂度 ratchet 和 git diff --check 通过。

app/chain/scraping.py

@@ -1906,6 +1906,12 @@ class ScrapingChain(ChainBase, ConfigReloadMixin, metaclass=Singleton):
     def _write_music_text_sidecar(target: Path, content: str) -> None:
         """
         同目录原子替换歌词目录项，避免覆盖已有硬/软链接时改写PT源旁挂文件。
+
+        新建和覆盖文件均遵循刮削文件的 UMASK 规则，不沿用临时文件的私有权限。
+
+        :param target: 媒体库中需要新建或替换的歌词路径
+        :param content: 使用 UTF-8 保存的歌词正文
+        :raises OSError: 创建、设置权限或替换失败，原歌词保持不变并清理临时文件
         """
         temporary: Optional[Path] = None
         try:
@@ -1913,6 +1919,7 @@ class ScrapingChain(ChainBase, ConfigReloadMixin, metaclass=Singleton):
                                     prefix=f".{target.name[:40]}.", delete=False) as stream:
                 temporary = Path(stream.name)
                 stream.write(f"{content.rstrip()}\n")
+            temporary.chmod(0o666 & ~current_umask)
             temporary.replace(target)
         finally:
             if temporary is not None:

tests/test_music_lyrics_permissions.py

@@ -0,0 +1,101 @@
+"""
+本地歌词原子写入的权限、链接保护及失败清理回归。
+"""
+
+import os
+from pathlib import Path
+from unittest.mock import Mock
+
+import pytest
+
+from app.chain import scraping
+
+pytestmark = pytest.mark.skipif(os.name != "posix", reason="仅 POSIX 平台支持完整文件权限语义")
+
+
+@pytest.mark.parametrize("extension", [".txt", ".lrc", ".lyricsfile.yaml"])
+@pytest.mark.parametrize("umask,expected_mode", [(0o000, 0o666), (0o022, 0o644), (0o027, 0o640), (0o077, 0o600)])
+def test_new_music_sidecar_respects_umask(
+        tmp_path: Path, monkeypatch: pytest.MonkeyPatch, extension: str, umask: int, expected_mode: int,
+) -> None:
+    """
+    新建三种歌词旁挂均遵循部署权限规则，允许媒体服务器按配置读取。
+    """
+    monkeypatch.setattr(scraping, "current_umask", umask)
+    target = tmp_path / f"track{extension}"
+
+    scraping.ScrapingChain._write_music_text_sidecar(target, "南方姑娘\n")
+
+    assert target.stat().st_mode & 0o777 == expected_mode
+    assert target.read_text(encoding="utf-8") == "南方姑娘\n"
+    assert list(tmp_path.iterdir()) == [target]
+
+
+@pytest.mark.parametrize("original_mode", [0o600, 0o664])
+@pytest.mark.parametrize("umask,expected_mode", [(0o022, 0o644), (0o077, 0o600)])
+def test_replaced_music_sidecar_respects_umask(
+        tmp_path: Path, monkeypatch: pytest.MonkeyPatch, original_mode: int, umask: int, expected_mode: int,
+) -> None:
+    """
+    覆盖写入同样应用部署规则，修正旧私有歌词并尊重显式限制读取的部署。
+    """
+    monkeypatch.setattr(scraping, "current_umask", umask)
+    target = tmp_path / "track.txt"
+    target.write_text("旧歌词", encoding="utf-8")
+    target.chmod(original_mode)
+
+    scraping.ScrapingChain._write_music_text_sidecar(target, "新歌词")
+
+    assert target.stat().st_mode & 0o777 == expected_mode
+    assert target.read_text(encoding="utf-8") == "新歌词\n"
+    assert list(tmp_path.iterdir()) == [target]
+
+
+@pytest.mark.parametrize("link_type", ["hardlink", "symlink", "dangling_symlink"])
+def test_music_sidecar_permissions_do_not_change_linked_source(
+        tmp_path: Path, monkeypatch: pytest.MonkeyPatch, link_type: str,
+) -> None:
+    """
+    仅设置独立副本权限并替换目录项，种源字节和权限均不受影响。
+    """
+    monkeypatch.setattr(scraping, "current_umask", 0o022)
+    source = tmp_path / "seed.lrc"
+    target = tmp_path / "track.lrc"
+    if link_type != "dangling_symlink":
+        source.write_text("种源歌词", encoding="utf-8")
+        source.chmod(0o640)
+    if link_type == "hardlink":
+        target.hardlink_to(source)
+    else:
+        target.symlink_to(source)
+
+    scraping.ScrapingChain._write_music_text_sidecar(target, "媒体库歌词")
+
+    assert not target.is_symlink()
+    assert target.stat().st_mode & 0o777 == 0o644
+    assert target.read_text(encoding="utf-8") == "媒体库歌词\n"
+    if link_type == "dangling_symlink":
+        assert not source.exists()
+    else:
+        assert source.read_text(encoding="utf-8") == "种源歌词"
+        assert source.stat().st_mode & 0o777 == 0o640
+
+
+@pytest.mark.parametrize("operation", ["chmod", "replace"])
+def test_music_sidecar_publish_failure_keeps_original_and_removes_temporary(
+        tmp_path: Path, monkeypatch: pytest.MonkeyPatch, operation: str,
+) -> None:
+    """
+    权限设置或原子替换失败时保留原歌词，并清理未发布的临时文件。
+    """
+    target = tmp_path / "track.txt"
+    target.write_text("原歌词", encoding="utf-8")
+    target.chmod(0o640)
+    monkeypatch.setattr(Path, operation, Mock(side_effect=PermissionError("拒绝发布")))
+
+    with pytest.raises(PermissionError, match="拒绝发布"):
+        scraping.ScrapingChain._write_music_text_sidecar(target, "新歌词")
+
+    assert target.read_text(encoding="utf-8") == "原歌词"
+    assert target.stat().st_mode & 0o777 == 0o640
+    assert list(tmp_path.iterdir()) == [target]