Archived
refactor: 播客流式下载拆解（嵌套 10 层 → 1，三段职责各就其位）
为什么：_podcast_stream_download 是播客单集下载的**唯一落盘路径**（单集 worker 与整台打包的首集都走它），却零测试覆盖；而且它把三段互不相关的职责——全局名额 排队、流式写盘与进度上报、完整性校验与坏文件清理——叠在 try/with/with/for 加四层 if 里，最大嵌套 10 层，是全仓最深的一个。 改法：拆成四个具名函数，主函数只留编排。 _stream_to_part ：拿响应 → 写 .part → 按 0.5s 节流上报进度，返回 (已写, 期望) _report_progress ：把一次进度写进任务表（含单集任务的 live_percent） _verify_downloaded ：完整性判定 + 清掉坏文件（精确相等 / 非空两条口径） _remove_quietly ：删文件并吞掉 OSError（Windows 句柄未释放时 remove 会抛） 复杂度（同口径 AST 实测）： _podcast_stream_download 63 行 / 圈 19 / 嵌套 10 → 21 行 / 圈 3 / 嵌套 1 新增 _stream_to_part 25 行/圈 8/嵌套 4 · _report_progress 22/6/3 · _verify_downloaded 14/3/1 文件内嵌套 ≥5 层 2 → 1（余下那个是本次未动的 _podcast_download_worker） 刻意保留的语义（是决定，不是疏漏）： - 取消时 **.part 留存不删**（改名不发生，下次同名下载直接覆盖）——已用测试固化。 不「顺手」改成删除，那是行为变更。 - 进度 msg 的计算与「是否真有可取的任务」无关：task_id 为空时仍会格式化字符串再 return。这是既有的无害浪费，一并保留。 - 完整性口径原样：已知期望大小要求**精确相等**（放宽到 95% 容差会交付截断的坏文件 还照扣次数），期望未知则退化为非空校验。 等价性证据（两道）： 1. 反向注入验证：把 HEAD 的旧实现换回去，用同一套 tests/test_podcast_stream.py 跑 → 12 例**全过**，证明这批测试忠实编码旧行为、对新实现构成等价性验证。 2. 新增 12 例行为契约（该函数此前零覆盖）：正常落盘与改名、空分块跳过、 Content-Length 兜底、字节数不符清坏文件、空下载报错、已知大小不容忍部分交付、 上游 4xx、开始前取消、中途取消留 .part、running 任务写 msg/live_percent、 终态任务不被覆盖、无 task_id 不报错。 顺带记录一个测试自身的坑：替身响应最初用 list(chunks) 归一化，导致传入生成器的 副作用（中途置取消位）在**构造时刻**就执行，测出来变成「开始前取消」——两条本不 相同的路径被混成一条。已改为保留原 iterable 并写明原因。 验证：ruff 全过 · pyright 0/0 · pytest 245 passed（233→245）· 生产 data/ 未被触碰。
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@@ -56,21 +56,46 @@ def _podcast_safe_name(s: str, fallback: str = 'unknown') -> str:
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return s or fallback
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def _podcast_stream_download(url: str, target: Path, total_size: int,
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cancel_ev: threading.Event,
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task_id: str = '', progress_label: str = '') -> int:
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"""流式下载播客音频到 target（先写 .part 再改名），返回实际字节数
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def _remove_quietly(path: Path) -> None:
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"""删除文件并忽略失败（Windows 上句柄未释放时 os.remove 会抛 OSError）。"""
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try:
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os.remove(str(path))
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except OSError:
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pass
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自动加入全局下载信号量排队；每 0.5s 更新一次任务进度消息。
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def _report_progress(task_id: str, progress_label: str, done: int, total: int) -> None:
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"""把一次进度写进任务表；task_id 为空或任务不在 running 时只计算不写。
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msg 的计算与「是否真有可取的任务」无关（历史实现如此），故 task_id 为空时
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仍会格式化字符串——保持这一无害的既有行为，不做「优化」。
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"""
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pct = 0
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if total:
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pct = min(99, int(done / total * 100))
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msg = (f"{progress_label} {pct}% · "
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f"{api_service._format_file_size(done)}/{api_service._format_file_size(total)}")
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else:
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msg = f"{progress_label} 已下载 {api_service._format_file_size(done)}"
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if not task_id:
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return
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with DOWNLOAD_TASKS_LOCK:
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t = DOWNLOAD_TASKS.get(task_id)
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if t and t['status'] == 'running':
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t['msg'] = msg
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# 单集任务的字节级进度（批量任务保持按集数口径）
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if t.get('type') == 'single' and total:
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t['live_percent'] = min(99.0, float(pct))
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def _stream_to_part(url: str, part: Path, total_size: int, cancel_ev: threading.Event,
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task_id: str, progress_label: str) -> tuple[int, int]:
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"""把响应体流式写入 part，返回 (已写字节数, 期望总大小)。
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期望总大小取入参，缺失时回落到 Content-Length（仍可能为 0，表示上游没给）。
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"""
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done = 0
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last_update = 0.0
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part = target.with_name(target.name + '.part')
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# 等待全局下载名额期间可被取消（与音乐批量 BATCH_ZIP_SEM 同语义）
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sem = api_service.downloader._download_semaphore
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if not sem.acquire_cancellable(cancel_ev):
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raise DownloadCanceled("任务已取消")
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try:
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with _stream_open(url, timeout=60) as r:
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if r.status >= 400:
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raise DownloadException(f"上游返回 {r.status}")
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@@ -79,45 +104,53 @@ def _podcast_stream_download(url: str, target: Path, total_size: int,
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for chunk in r.iter_content(chunk_size=256 * 1024):
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if cancel_ev.is_set():
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raise DownloadCanceled("任务已取消")
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if chunk:
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if not chunk:
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continue
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f.write(chunk)
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done += len(chunk)
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now = time.time()
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if now - last_update > 0.5:
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last_update = now
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pct = 0
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if total:
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pct = min(99, int(done / total * 100))
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msg = f"{progress_label} {pct}% · {api_service._format_file_size(done)}/{api_service._format_file_size(total)}"
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else:
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msg = f"{progress_label} 已下载 {api_service._format_file_size(done)}"
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if task_id:
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with DOWNLOAD_TASKS_LOCK:
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t = DOWNLOAD_TASKS.get(task_id)
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if t and t['status'] == 'running':
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t['msg'] = msg
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# 单集任务的字节级进度（批量任务保持按集数口径）
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if t.get('type') == 'single' and total:
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t['live_percent'] = min(99.0, float(pct))
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_report_progress(task_id, progress_label, done, total)
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return done, total
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def _verify_downloaded(target: Path, done: int, total_size: int) -> None:
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"""完整性校验：不达标则删掉已落地的文件并抛 DownloadException。
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为什么非要校验：CDN 提前断流时 iter_content 会「正常」结束，文件静默截断。
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已知期望大小时要求**精确相等**（API 报的大小与实际一致；放宽到 95% 容差会
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交付截断的坏文件还照扣次数）；期望未知时退化为非空校验——Content-Length
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兜底值可能是压缩口径，不做精确比对。
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"""
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if total_size and done != total_size:
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_remove_quietly(target)
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raise DownloadException(f"下载不完整（{done}/{total_size} 字节），请重试")
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if not total_size and done <= 0:
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_remove_quietly(target)
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raise DownloadException("下载内容为空，请重试")
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def _podcast_stream_download(url: str, target: Path, total_size: int,
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cancel_ev: threading.Event,
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task_id: str = '', progress_label: str = '') -> int:
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"""流式下载播客音频到 target（先写 .part 再改名），返回实际字节数。
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自动加入全局下载信号量排队；每 0.5s 更新一次任务进度消息。
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取消时 .part 会留存（不删）——下次下载同名文件直接覆盖，是既有行为。
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"""
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part = target.with_name(target.name + '.part')
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# 等待全局下载名额期间可被取消（与音乐批量 BATCH_ZIP_SEM 同语义）
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sem = api_service.downloader._download_semaphore
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if not sem.acquire_cancellable(cancel_ev):
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raise DownloadCanceled("任务已取消")
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try:
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done, _total = _stream_to_part(url, part, total_size, cancel_ev, task_id, progress_label)
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finally:
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sem.release()
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if part.exists():
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part.replace(target)
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# 完整性校验：CDN 提前断流时 iter_content 会"正常"结束，文件静默截断
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# （API 报告的期望大小时精确相等——95% 容差会交付截断的坏文件还扣次数；
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# 期望未知时退化为非空校验，Content-Length 兜底值可能是压缩口径不做精确比对）
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if total_size and done != total_size:
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try:
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os.remove(str(target))
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except OSError:
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pass
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raise DownloadException(f"下载不完整（{done}/{total_size} 字节），请重试")
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if not total_size and done <= 0:
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try:
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os.remove(str(target))
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except OSError:
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pass
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raise DownloadException("下载内容为空，请重试")
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_verify_downloaded(target, done, total_size)
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return done
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@@ -0,0 +1,220 @@
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# -*- coding: utf-8 -*-
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"""`_podcast_stream_download` 的行为契约。
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为什么：这是播客单集下载的**唯一落盘路径**（单集 worker 与整台打包的首集都走它），
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却零测试覆盖。把 63 行 / 嵌套 10 层的实现拆成「拿名额 → 流式写 → 改名 → 校验」
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四步后，需要行为级测试钉住可观察契约：返回字节数、半成品文件名、失败时是否清掉
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已落地的坏文件、取消语义、进度消息写到哪。
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断言只看「调用后世界里发生了什么」（文件系统 + 任务表），不引用私有函数名，
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故可跨后续重构复用。
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"""
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import threading
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import pytest
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from core.state import DOWNLOAD_TASKS, DOWNLOAD_TASKS_LOCK
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from music_downloader import DownloadCanceled, DownloadException
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from services import podcast as podcast_svc
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class _FakeResp:
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"""`_stream_open` 的替身：可控状态码、Content-Length 与分块序列。
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注意不能用 list(chunks) 归一化——那会把传入的生成器**立即求值**，使「迭代中
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才触发的副作用」（如中途置取消位）提前到构造时刻，测出来的就不是想测的路径。
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"""
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def __init__(self, chunks, status=200, content_length=None):
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self._chunks = chunks
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self.status = status
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self.headers = {} if content_length is None else {'Content-Length': str(content_length)}
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def __enter__(self):
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return self
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def __exit__(self, *exc):
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return False
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def iter_content(self, chunk_size=0):
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yield from self._chunks
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class _CancelAfterFirstChunk:
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"""迭代器：吐第一块后置取消位，再吐第二块。
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这样取消发生在**迭代过程中**（下载已开始、.part 已建立），与「开始前取消」
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是两条不同的路径。
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"""
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def __init__(self, cancel):
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self._cancel = cancel
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self._n = 0
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def __iter__(self):
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return self
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def __next__(self):
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self._n += 1
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if self._n == 1:
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return b'x' * 10
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if self._n == 2:
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self._cancel.set()
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return b'y' * 10
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raise StopIteration
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@pytest.fixture()
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def fake_stream(monkeypatch):
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"""替换 _stream_open；测试通过 holder['resp'] 指定本次响应。"""
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holder: dict = {}
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def _open(url, timeout=60):
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assert url == holder.get('url', url)
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return holder['resp']
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monkeypatch.setattr(podcast_svc, '_stream_open', _open)
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return holder
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@pytest.fixture()
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def task_table():
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"""在全局任务表里放一条任务，测试结束清理（该表是跨模块共享的进程内状态）。"""
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tid = 'stream-test-task'
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def _put(**kw):
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task = {'id': tid, 'status': 'running', 'type': 'single', 'msg': ''}
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task.update(kw)
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with DOWNLOAD_TASKS_LOCK:
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DOWNLOAD_TASKS[tid] = task
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return task
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yield _put
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with DOWNLOAD_TASKS_LOCK:
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DOWNLOAD_TASKS.pop(tid, None)
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# ============ 正常路径 ============
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def test_writes_target_and_renames_part(tmp_path, fake_stream):
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"""正常下载：返回实际字节数，落地 target，不残留 .part。"""
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fake_stream['resp'] = _FakeResp([b'a' * 600, b'b' * 400])
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target = tmp_path / 'ep.mp3'
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done = podcast_svc._podcast_stream_download('http://u', target, 1000, threading.Event())
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assert done == 1000
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assert target.read_bytes() == b'a' * 600 + b'b' * 400
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assert not target.with_name('ep.mp3.part').exists()
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def test_empty_chunks_are_skipped(tmp_path, fake_stream):
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"""空分块不计入字节数（上游偶发发空 chunk）。"""
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fake_stream['resp'] = _FakeResp([b'', b'x' * 50, b''])
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target = tmp_path / 'ep.mp3'
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assert podcast_svc._podcast_stream_download('http://u', target, 50, threading.Event()) == 50
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def test_content_length_used_when_total_unknown(tmp_path, fake_stream):
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"""未传期望大小时用 Content-Length 兜底，并据此校验完整性。"""
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fake_stream['resp'] = _FakeResp([b'x' * 30], content_length=30)
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target = tmp_path / 'ep.mp3'
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assert podcast_svc._podcast_stream_download('http://u', target, 0, threading.Event()) == 30
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# ============ 完整性校验 ============
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def test_size_mismatch_removes_delivered_file(tmp_path, fake_stream):
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"""字节数不符：删掉已落地的文件并报错（不交付截断的坏文件）。"""
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fake_stream['resp'] = _FakeResp([b'x' * 100])
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target = tmp_path / 'ep.mp3'
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with pytest.raises(DownloadException) as ei:
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podcast_svc._podcast_stream_download('http://u', target, 200, threading.Event())
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assert '下载不完整' in str(ei.value)
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assert not target.exists(), '坏文件必须被清掉'
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def test_empty_download_raises_and_removes(tmp_path, fake_stream):
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"""期望大小未知且一个字节都没拿到 → 报「下载内容为空」。"""
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fake_stream['resp'] = _FakeResp([])
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target = tmp_path / 'ep.mp3'
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with pytest.raises(DownloadException) as ei:
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podcast_svc._podcast_stream_download('http://u', target, 0, threading.Event())
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assert '下载内容为空' in str(ei.value)
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assert not target.exists()
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def test_known_size_does_not_tolerate_partial(tmp_path, fake_stream):
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"""已知期望大小时要求精确相等——95% 容差会放行截断的坏文件。"""
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fake_stream['resp'] = _FakeResp([b'x' * 95])
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target = tmp_path / 'ep.mp3'
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with pytest.raises(DownloadException):
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podcast_svc._podcast_stream_download('http://u', target, 100, threading.Event())
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# ============ 上游与取消 ============
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def test_upstream_error_status_raises(tmp_path, fake_stream):
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fake_stream['resp'] = _FakeResp([], status=404)
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target = tmp_path / 'ep.mp3'
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with pytest.raises(DownloadException) as ei:
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podcast_svc._podcast_stream_download('http://u', target, 100, threading.Event())
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assert '上游返回 404' in str(ei.value)
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assert not target.exists()
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def test_cancel_before_first_chunk(tmp_path, fake_stream):
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"""取消已置位：抛 DownloadCanceled，不发布 target。"""
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cancel = threading.Event()
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cancel.set()
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fake_stream['resp'] = _FakeResp([b'x' * 10])
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target = tmp_path / 'ep.mp3'
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with pytest.raises(DownloadCanceled):
|
||||
podcast_svc._podcast_stream_download('http://u', target, 10, cancel)
|
||||
assert not target.exists()
|
||||
|
||||
|
||||
def test_cancel_midway_leaves_part_file(tmp_path, fake_stream):
|
||||
"""下载中途取消：.part 残留（不删）——改名不发生，下次同名下载直接覆盖。"""
|
||||
cancel = threading.Event()
|
||||
fake_stream['resp'] = _FakeResp(_CancelAfterFirstChunk(cancel))
|
||||
target = tmp_path / 'ep.mp3'
|
||||
with pytest.raises(DownloadCanceled):
|
||||
podcast_svc._podcast_stream_download('http://u', target, 20, cancel)
|
||||
assert not target.exists()
|
||||
assert target.with_name('ep.mp3.part').exists(), '既有行为：取消时 .part 留存'
|
||||
|
||||
|
||||
# ============ 进度消息 ============
|
||||
|
||||
|
||||
def test_progress_written_for_running_single_task(tmp_path, fake_stream, task_table):
|
||||
"""running 的单集任务：写 msg，并按字节级口径写 live_percent。
|
||||
|
||||
单块即完成 → 百分比被 min(99, ...) 封在 99（进度条不预支 100%，收尾靠终态）。
|
||||
"""
|
||||
task = task_table()
|
||||
fake_stream['resp'] = _FakeResp([b'x' * 100])
|
||||
target = tmp_path / 'ep.mp3'
|
||||
podcast_svc._podcast_stream_download('http://u', target, 100, threading.Event(),
|
||||
task_id=task['id'], progress_label='下载中')
|
||||
assert '下载中' in task['msg'] and '99%' in task['msg']
|
||||
assert task['live_percent'] == 99.0
|
||||
|
||||
|
||||
def test_progress_not_written_for_finished_task(tmp_path, fake_stream, task_table):
|
||||
"""已终态的任务不再被写进度（避免覆盖终态消息），但下载照常完成。"""
|
||||
task = task_table(status='done', msg='原消息')
|
||||
fake_stream['resp'] = _FakeResp([b'x' * 50])
|
||||
target = tmp_path / 'ep.mp3'
|
||||
assert podcast_svc._podcast_stream_download('http://u', target, 50, threading.Event(),
|
||||
task_id=task['id']) == 50
|
||||
assert task['msg'] == '原消息'
|
||||
|
||||
|
||||
def test_progress_skipped_without_task_id(tmp_path, fake_stream):
|
||||
"""task_id 为空时只下载不写任务表（不得因缺 id 而报错）。"""
|
||||
fake_stream['resp'] = _FakeResp([b'x' * 50])
|
||||
target = tmp_path / 'ep.mp3'
|
||||
assert podcast_svc._podcast_stream_download('http://u', target, 50, threading.Event()) == 50
|
||||
Reference in new issue
Block a user