fix: offload subtitle download after add task

tests/test_download_chain.py

@@ -0,0 +1,97 @@
+from pathlib import Path
+from unittest.mock import MagicMock
+
+import app.chain.download as download_module
+from app.chain.download import DownloadChain
+from app.core.context import Context, MediaInfo, TorrentInfo
+from app.core.metainfo import MetaInfo
+from app.schemas.types import MediaType
+
+
+class _FakeDownloadHistoryOper:
+    """
+    避免单元测试写入真实下载历史，只验证下载链路的控制流。
+    """
+
+    def add(self, **_kwargs):
+        pass
+
+    def add_files(self, _files):
+        pass
+
+
+class _FakeTorrentHelper:
+    """
+    避免解析真实种子内容，让测试聚焦下载成功后的后台处理。
+    """
+
+    def get_fileinfo_from_torrent_content(self, _torrent_content):
+        return "", []
+
+
+class _FakeThreadHelper:
+    """
+    捕获提交到线程池的任务，测试中手动触发以避免真正启动后台线程。
+    """
+
+    submitted = []
+
+    def submit(self, func, *args, **kwargs):
+        self.submitted.append((func, args, kwargs))
+
+
+def test_download_single_submits_download_added_to_background(monkeypatch):
+    """
+    添加下载成功后，站点字幕等后处理应提交到后台，不能阻塞下载接口返回。
+    """
+    _FakeThreadHelper.submitted = []
+    monkeypatch.setattr(download_module, "ThreadHelper", _FakeThreadHelper)
+    monkeypatch.setattr(download_module, "DownloadHistoryOper", _FakeDownloadHistoryOper)
+    monkeypatch.setattr(download_module, "TorrentHelper", _FakeTorrentHelper)
+
+    chain = DownloadChain.__new__(DownloadChain)
+    chain.download = MagicMock(return_value=("qb", "hash123", "Original", "添加下载成功"))
+    chain.download_added = MagicMock()
+    chain.eventmanager = MagicMock()
+    chain.eventmanager.send_event.return_value = None
+    chain.post_message = MagicMock()
+
+    context = Context(
+        meta_info=MetaInfo("Demo Movie 2024"),
+        media_info=MediaInfo(
+            type=MediaType.MOVIE,
+            title="Demo Movie",
+            year="2024",
+            tmdb_id=1,
+            genre_ids=[18],
+        ),
+        torrent_info=TorrentInfo(
+            title="Demo Movie 2024",
+            enclosure="https://example.com/demo.torrent",
+            site_cookie="uid=1",
+            site_name="TestSite",
+        ),
+    )
+
+    result = chain.download_single(
+        context=context,
+        torrent_content=b"torrent-content",
+        save_path="/downloads",
+        username="tester",
+    )
+
+    assert result == "hash123"
+    chain.download_added.assert_not_called()
+    assert len(_FakeThreadHelper.submitted) == 1
+
+    task, args, kwargs = _FakeThreadHelper.submitted[0]
+    assert args == ()
+    assert kwargs == {}
+
+    task()
+
+    chain.download_added.assert_called_once_with(
+        context=context,
+        download_dir=Path("/downloads"),
+        torrent_content=b"torrent-content",
+    )