Archived
snowy-yang
8716617d5d
为什么：download_music_file 是**唯一**的音频落盘路径（单曲 worker、音乐批量 ZIP
都经它），205 行 / 圈复杂度 47 / 嵌套 7 的单体里叠着缓存校验、断点续传、内容嗅探、
体积上限、取消语义、重试退避、元数据限流七件事，却**零直接测试覆盖**
（test_zip_workers 里只有一个 stub）。任何一处被改坏都不会有测试报警。
改法：拆成 8 个具名方法，主函数只留「5 步管线 + 重试策略」：
_cached_result 锁内复查缓存（命中即返回，坏缓存删除重下）
_promote_complete_part 已下完未改名的 .part 直接转正，不发起网络请求
_resume_offset 断点续传起点，并清理没有续传价值的残片
_transfer 占全局名额 + 选通道（aria2c / 内置 aiohttp）
_size_mismatch_error 完整性判定（已知期望精确相等 / 未知期望至少非空）
_publish 嗅探 → 原子转正 → 写元数据
_write_metadata_locked 标签信号量内的元数据写入（原三处重复的 with 收敛）
_backoff_wait 退避秒数（原五处重复的 0.5*(attempt+1) 收敛）
复杂度（同口径 AST 实测）：
download_music_file 205 行 / 圈 47 / 嵌套 7 → 125 行 / 圈 20 / 嵌套 4
（125 行里 26 行是 docstring，正文 87 行）
文件内嵌套 >=5 层 2 → 1（余下的是本次未动的 _fetch_via_http）
文件内最大圈复杂度 47 → 35（同样落在未动的 _fetch_via_http 上）
文件行数 614 → 710（+96，全是新签名与 docstring）
等价性证据（两道，互相独立）：
1. 29 例行为契约测试**在未改动的原始实现上一次性全绿**（先写测试、后动代码；改完
再跑仍全绿）——这批测试因此忠实编码了旧行为，构成等价性验证，而不是「照着新
实现写的新行为测试」。断言只依赖返回值 / 磁盘上的文件 / 发往网络的请求，不引用
任何内部函数名，故可跨后续重构复用。
2. AST 字面量多重集比对 + **逐条位置定位**：数值/布尔 27 种、字符串 80 种。差异
全部归因，且**没有一条用户可见文案或阈值被改动**——
0 +2：_resume_offset 的三个 return 0 取代原 resume_from = 0
0.0 +1、0.5 −3、1 −3：四处重复的 0.5*(attempt+1) 收敛进 _backoff_wait
None +16：新增方法的 6 处类型标注 + 4 处 return None + 2 处 is not None
'' +1：_size_mismatch_error 的内部哨兵（非用户可见）
续传起点逻辑另做逐例核对：promote 命中 / existing<=0 / 超尺寸 / 部分 四路等价。
刻意保留的语义（是决定，不是疏漏）：
- 退避睡眠仍在文件锁外执行——同名并发任务不陪睡。
- 缓存命中时若 write_meta 仍按本次请求重跑一次标签写入（幂等）；write_meta=False
则不写。
- 已转正（os.replace 之后）才发现取消时**不回滚文件**，只跳过元数据——原行为如此，
已用 test_cancel_after_promote_keeps_file_but_skips_metadata 固化。
- 未知期望尺寸（file_size=0）走「非空即通过」+ 内容嗅探兜底；已知期望尺寸要求
**精确相等**（放宽到容差会交付截断的坏文件还照扣次数）。
- 缓存有效性用 st_size != file_size（而非 >=）：跨账号音质降级 / 上游变更都会让
同 ID 同音质的实际文件不同，命中即返回会把旧文件当本次结果交付。
测试：新增 tests/test_downloader.py（29 例）——正常落盘与 .part 转正、空分块跳过、
进度回调（起点 / 每块 / 异常吞掉）、缓存命中不发请求、坏缓存重下、0 字节缓存拒绝、
续传发 Range 并追加、服务器忽略 Range 时重写、完整残片免网络转正、超尺寸残片丢弃、
206 起点错位 / 206 缺 Content-Range / 416 三路从头重下、CDN 4xx 不重试、408 可重试、
不完整保留 .part、下轮续传、未知尺寸非音频拒绝、体积上限、五种取消路径、元数据开关。
验证：ruff 全过 · pyright 0/0 · pytest 274 passed（245→274）· 生产 data/ 未被触碰
（全部用例走 tmp_path 沙箱）。
582 lines
19 KiB
Python
582 lines
19 KiB
Python
# -*- coding: utf-8 -*-
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"""MusicDownloader.download_music_file 的行为契约测试（沙箱，不触碰生产 data/）。
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为什么：download_music_file 是**唯一**的音频落盘路径——单曲 worker 与音乐批量
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ZIP 都经它，约 205 行 / 圈复杂度 47，此前**零直接测试覆盖**（test_zip_workers 里
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只有一个 stub）。它同时承担缓存校验、断点续传、内容嗅探、体积上限、取消语义、
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重试退避与元数据写入，任何一条被拆坏都不会有测试报警。
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断言只依赖「调用后世界里发生了什么」——返回值、磁盘上的文件、发往网络的请求——
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不引用任何内部函数名，因此本文件可作为后续拆分的等价性验证器。
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替身约定（三处，均为模块级符号，替换点在 downloader 模块命名空间）：
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- 网络：``get_http_session`` / ``get_backend``（后者返回 None = 走内置 HTTP 通道）
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- 内容嗅探：``_sniff_audio_header``（默认放行，按需置 False）
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- 元数据写入：``MusicDownloader._write_metadata``（不真跑 mutagen）
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"""
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import threading
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from pathlib import Path
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from typing import Any
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import pytest
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from core import sync_http
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from music_downloader import DownloadCanceled, DownloadException, MusicInfo
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from music_downloader.downloader import MusicDownloader
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# ============ 替身 ============
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class _FakeResponse:
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"""core.sync_http.SyncResponse 的替身。
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chunks 保留原始 iterable（**不要** list() 归一化）：生成器的副作用
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（如中途置取消位）若在构造时刻就求值，「中途取消」会被悄悄测成
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「开始前取消」——两条不同的路径混成一条，而测试仍是绿的。
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"""
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def __init__(self, chunks, status=200, headers=None):
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self._chunks = chunks
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self.status_code = status
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self.headers = dict(headers or {})
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self.closed = False
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def iter_content(self, chunk_size=0):
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yield from self._chunks
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def raise_for_status(self):
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if self.status_code >= 400:
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raise sync_http.HTTPError(f'HTTP {self.status_code}', self)
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def close(self):
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self.closed = True
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class _FakeSession:
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"""记录每次 GET（含 headers）并按序产出响应。"""
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def __init__(self, responder):
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self._responder = responder
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self.calls: list[tuple[str, dict[str, Any]]] = []
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self.closed = False
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def get(self, url, **kw):
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self.calls.append((url, kw))
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return self._responder(len(self.calls), url, kw)
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def close(self):
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self.closed = True
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def _body(size, status=200, content_range=None):
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"""固定返回 size 字节的响应工厂（每次调用产出新响应对象）。"""
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def _mk(_attempt, _url, _kw):
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headers = {'Content-Range': content_range} if content_range else {}
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return _FakeResponse([b'x' * size], status=status, headers=headers)
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return _mk
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def _info(mid=101, size=20, file_type='mp3'):
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return MusicInfo(
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id=mid, name='测试曲', artists='歌手', album='专辑', pic_url='',
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duration=180, track_number=1, download_url='http://cdn.test/a.mp3',
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file_type=file_type, file_size=size, quality='standard',
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)
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def _paths(dl, info):
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"""按生产同一函数推算落盘路径与 .part 路径（纯函数，可直接复用）。"""
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fp = dl._build_file_path(info)
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return fp, fp.with_name(fp.name + '.part')
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@pytest.fixture()
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def env(tmp_path, monkeypatch):
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"""返回 (downloader, state, install)。
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- state['sniff']：内容嗅探结果，默认 True
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- state['meta']：_write_metadata 的调用记录 [(文件路径, fields), ...]
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- install(responder) -> _FakeSession：安装网络替身，返回该替身以便断言
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"""
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state: dict[str, Any] = {'sniff': True, 'meta': []}
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box: dict[str, _FakeSession] = {}
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def install(responder):
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box['session'] = _FakeSession(responder)
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return box['session']
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def _record_meta(self, file_path, music_info, fields=None):
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state['meta'].append((str(file_path), fields))
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return True
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monkeypatch.setattr('music_downloader.downloader.get_http_session',
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lambda: box['session'])
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monkeypatch.setattr('music_downloader.downloader.get_backend', lambda: None)
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monkeypatch.setattr('music_downloader.downloader._sniff_audio_header',
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lambda _p: state['sniff'])
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monkeypatch.setattr(MusicDownloader, '_write_metadata', _record_meta)
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install(lambda *a: pytest.fail('本用例不应发出网络请求'))
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dl = MusicDownloader(download_dir=str(tmp_path))
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return dl, state, install
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# ============ 正常落盘 ============
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def test_success_promotes_part_to_final(env):
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dl, _state, install = env
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info = _info(size=20)
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fp, part = _paths(dl, info)
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install(_body(20))
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r = dl.download_music_file(101, music_info=info)
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assert r.success and r.error_message == ''
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assert Path(r.file_path) == fp
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assert r.file_size == 20 and fp.read_bytes() == b'x' * 20
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assert not part.exists(), '完成后 .part 应改名转正'
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def test_empty_chunks_skipped(env):
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dl, _state, install = env
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info = _info(size=20)
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fp, _ = _paths(dl, info)
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install(lambda a, u, kw: _FakeResponse([b'', b'x' * 20, b'']))
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seen: list[int] = []
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r = dl.download_music_file(101, music_info=info,
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progress_cb=lambda w, _t: seen.append(w))
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assert r.success and fp.stat().st_size == 20
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assert seen == [0, 20], '空分块不写盘也不触发进度回调'
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def test_progress_reports_resume_start_then_each_chunk(env):
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dl, _state, install = env
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info = _info(size=20)
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install(lambda a, u, kw: _FakeResponse([b'a' * 8, b'b' * 12]))
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seen: list[tuple[int, int]] = []
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r = dl.download_music_file(101, music_info=info,
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progress_cb=lambda w, t: seen.append((w, t)))
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assert r.success
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assert seen == [(0, 20), (8, 20), (20, 20)], '起始回调带续传起点，此后每块一次'
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def test_progress_callback_exception_never_breaks_download(env):
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dl, _state, install = env
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info = _info(size=20)
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install(_body(20))
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def _boom(_w, _t):
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raise RuntimeError('回调炸了')
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r = dl.download_music_file(101, music_info=info, progress_cb=_boom)
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assert r.success, '进度回调异常绝不影响下载主流程'
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def test_music_info_fetched_when_not_provided(env, monkeypatch):
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dl, _state, install = env
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info = _info(size=20)
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seen: list[tuple] = []
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monkeypatch.setattr(dl, 'get_music_info',
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lambda mid, q, c=None: (seen.append((mid, q)), info)[1])
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install(_body(20))
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r = dl.download_music_file(101, 'lossless')
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assert r.success and seen == [(101, 'lossless')]
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# ============ 缓存校验 ============
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def test_cache_hit_skips_network(env):
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dl, _state, install = env
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info = _info(size=20)
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fp, _ = _paths(dl, info)
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fp.write_bytes(b'c' * 20)
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session = install(lambda *a: pytest.fail('缓存命中不应发网络请求'))
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r = dl.download_music_file(101, music_info=info)
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assert r.success and r.file_size == 20
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assert session.calls == []
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def test_cache_size_mismatch_triggers_redownload(env):
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dl, _state, install = env
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info = _info(size=20)
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fp, _ = _paths(dl, info)
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fp.write_bytes(b'c' * 15) # 与本次期望不符 = 缓存 miss
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session = install(_body(20))
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r = dl.download_music_file(101, music_info=info)
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assert r.success and fp.read_bytes() == b'x' * 20
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assert len(session.calls) == 1, '坏缓存应被删除并重下，而不是当结果交付'
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def test_zero_byte_cache_rejected_when_expected_size_unknown(env):
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dl, _state, install = env
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info = _info(size=0)
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fp, _ = _paths(dl, info)
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fp.write_bytes(b'')
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session = install(lambda a, u, kw: _FakeResponse([b'good']))
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r = dl.download_music_file(101, music_info=info)
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assert r.success and fp.read_bytes() == b'good'
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assert len(session.calls) == 1, '期望未知时至少拒绝 0 字节坏文件'
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# ============ 断点续传 ============
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def test_resume_sends_range_and_appends(env):
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dl, _state, install = env
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info = _info(size=20)
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fp, part = _paths(dl, info)
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part.write_bytes(b'p' * 10)
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session = install(lambda a, u, kw: _FakeResponse(
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[b'q' * 10], status=206, headers={'Content-Range': 'bytes 10-19/20'}))
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seen: list[tuple[int, int]] = []
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r = dl.download_music_file(101, music_info=info,
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progress_cb=lambda w, t: seen.append((w, t)))
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assert r.success
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assert session.calls[0][1]['headers'].get('Range') == 'bytes=10-'
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assert fp.read_bytes() == b'p' * 10 + b'q' * 10, '续传应追加而非覆盖'
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assert seen[0] == (10, 20), '起始进度应带续传起点'
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def test_server_ignoring_range_rewrites_from_zero(env):
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dl, _state, install = env
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info = _info(size=20)
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fp, part = _paths(dl, info)
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part.write_bytes(b'p' * 10)
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install(lambda a, u, kw: _FakeResponse([b'r' * 20], status=200))
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r = dl.download_music_file(101, music_info=info)
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assert r.success and fp.read_bytes() == b'r' * 20, '服务器返回 200 须从头重写'
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def test_complete_part_promoted_without_network(env):
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dl, _state, install = env
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info = _info(size=20)
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fp, part = _paths(dl, info)
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part.write_bytes(b'z' * 20) # 已下完但未改名
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session = install(lambda *a: pytest.fail('完整残片不应发网络请求'))
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r = dl.download_music_file(101, music_info=info)
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assert r.success and r.file_size == 20
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assert session.calls == []
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assert fp.read_bytes() == b'z' * 20 and not part.exists()
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def test_oversized_part_discarded_starts_from_zero(env):
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dl, _state, install = env
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info = _info(size=20)
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_fp, part = _paths(dl, info)
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part.write_bytes(b'o' * 30) # 超尺寸残片没有续传价值
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session = install(_body(20))
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r = dl.download_music_file(101, music_info=info)
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assert r.success
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assert 'Range' not in session.calls[0][1]['headers']
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def test_zero_byte_part_discarded(env):
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dl, _state, install = env
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info = _info(size=20)
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_fp, part = _paths(dl, info)
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part.write_bytes(b'')
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session = install(_body(20))
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r = dl.download_music_file(101, music_info=info)
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assert r.success and 'Range' not in session.calls[0][1]['headers']
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def test_content_range_offset_mismatch_restarts_from_scratch(env):
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dl, _state, install = env
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info = _info(size=20)
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fp, part = _paths(dl, info)
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part.write_bytes(b'p' * 10)
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def responder(n, _url, _kw):
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if n == 1:
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return _FakeResponse([b'q' * 5], status=206,
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headers={'Content-Range': 'bytes 3-7/20'})
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return _FakeResponse([b'f' * 20], status=200)
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session = install(responder)
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r = dl.download_music_file(101, music_info=info, retries=1)
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assert r.success and len(session.calls) == 2
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assert 'Range' not in session.calls[1][1]['headers'], '清残片后应从头下'
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assert fp.read_bytes() == b'f' * 20
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def test_206_without_content_range_restarts_from_scratch(env):
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dl, _state, install = env
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info = _info(size=20)
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_fp, part = _paths(dl, info)
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part.write_bytes(b'p' * 10)
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def responder(n, _url, _kw):
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if n == 1:
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return _FakeResponse([b'q' * 5], status=206) # 头被中间层剥离
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return _FakeResponse([b'f' * 20], status=200)
|
||
|
||
session = install(responder)
|
||
|
||
r = dl.download_music_file(101, music_info=info, retries=1)
|
||
|
||
assert r.success and len(session.calls) == 2
|
||
assert 'Range' not in session.calls[1][1]['headers']
|
||
|
||
|
||
def test_http_416_restarts_from_scratch(env):
|
||
dl, _state, install = env
|
||
info = _info(size=20)
|
||
fp, part = _paths(dl, info)
|
||
part.write_bytes(b'p' * 10)
|
||
|
||
def responder(n, _url, _kw):
|
||
if n == 1:
|
||
return _FakeResponse([], status=416)
|
||
return _FakeResponse([b'f' * 20], status=200)
|
||
|
||
session = install(responder)
|
||
|
||
r = dl.download_music_file(101, music_info=info, retries=1)
|
||
|
||
assert r.success and len(session.calls) == 2
|
||
assert 'Range' not in session.calls[1][1]['headers']
|
||
assert fp.read_bytes() == b'f' * 20
|
||
|
||
|
||
# ============ 失败与重试 ============
|
||
|
||
|
||
def test_cdn_4xx_is_deterministic_and_not_retried(env):
|
||
dl, _state, install = env
|
||
info = _info(size=20)
|
||
session = install(lambda a, u, kw: _FakeResponse([], status=403))
|
||
|
||
with pytest.raises(DownloadException) as ei:
|
||
dl.download_music_file(101, music_info=info, retries=2)
|
||
|
||
assert 'HTTP 403' in str(ei.value)
|
||
assert len(session.calls) == 1, '确定性失败对同一失效直链白重试毫无意义'
|
||
|
||
|
||
def test_408_is_retried_then_reported_as_failure(env):
|
||
dl, _state, install = env
|
||
info = _info(size=20)
|
||
session = install(lambda a, u, kw: _FakeResponse([], status=408))
|
||
|
||
r = dl.download_music_file(101, music_info=info, retries=1)
|
||
|
||
assert not r.success
|
||
assert '下载请求失败' in r.error_message
|
||
assert len(session.calls) == 2, '408 请求超时应保留可重试'
|
||
|
||
|
||
def test_incomplete_size_keeps_part_and_reports(env):
|
||
dl, _state, install = env
|
||
info = _info(size=100)
|
||
fp, part = _paths(dl, info)
|
||
install(_body(10))
|
||
|
||
r = dl.download_music_file(101, music_info=info, retries=0)
|
||
|
||
assert not r.success and '下载不完整' in r.error_message
|
||
assert part.exists() and part.stat().st_size == 10, '.part 应保留以供续传'
|
||
assert not fp.exists(), '不完整的下载不得转正交付'
|
||
|
||
|
||
def test_incomplete_then_resumes_on_next_attempt(env):
|
||
dl, _state, install = env
|
||
info = _info(size=100)
|
||
_fp, part = _paths(dl, info)
|
||
|
||
def responder(n, _url, _kw):
|
||
if n == 1:
|
||
return _FakeResponse([b'a' * 10], status=200)
|
||
return _FakeResponse([b'b' * 5], status=206,
|
||
headers={'Content-Range': 'bytes 10-14/100'})
|
||
|
||
session = install(responder)
|
||
|
||
r = dl.download_music_file(101, music_info=info, retries=1)
|
||
|
||
assert not r.success and '下载不完整' in r.error_message
|
||
assert session.calls[1][1]['headers'].get('Range') == 'bytes=10-', '下轮应续传'
|
||
assert part.stat().st_size == 15
|
||
|
||
|
||
def test_network_error_keeps_part_for_resume(env):
|
||
dl, _state, install = env
|
||
info = _info(size=100)
|
||
fp, part = _paths(dl, info)
|
||
|
||
def chunks():
|
||
yield b'a' * 10
|
||
raise sync_http.RequestException('连接中断')
|
||
|
||
install(lambda a, u, kw: _FakeResponse(chunks()))
|
||
|
||
r = dl.download_music_file(101, music_info=info, retries=0)
|
||
|
||
assert not r.success and '下载请求失败' in r.error_message
|
||
assert part.exists() and part.stat().st_size == 10, '网络错误应保留 .part'
|
||
assert not fp.exists()
|
||
|
||
|
||
# ============ 内容校验与体积上限 ============
|
||
|
||
|
||
def test_unknown_size_non_audio_content_rejected(env):
|
||
dl, state, install = env
|
||
info = _info(size=0)
|
||
fp, part = _paths(dl, info)
|
||
state['sniff'] = False
|
||
install(lambda a, u, kw: _FakeResponse([b'<html>blocked</html>']))
|
||
|
||
with pytest.raises(DownloadException) as ei:
|
||
dl.download_music_file(101, music_info=info)
|
||
|
||
assert '非音频数据' in str(ei.value)
|
||
assert not part.exists() and not fp.exists()
|
||
|
||
|
||
def test_unknown_size_audio_content_accepted(env):
|
||
dl, state, install = env
|
||
info = _info(size=0)
|
||
fp, _ = _paths(dl, info)
|
||
state['sniff'] = True
|
||
install(lambda a, u, kw: _FakeResponse([b'ID3audio']))
|
||
|
||
r = dl.download_music_file(101, music_info=info)
|
||
|
||
assert r.success and fp.read_bytes() == b'ID3audio'
|
||
|
||
|
||
def test_size_limit_discards_part_and_fails(env, monkeypatch):
|
||
dl, _state, install = env
|
||
monkeypatch.setattr('music_downloader.downloader._MAX_DOWNLOAD_BYTES', 16)
|
||
info = _info(size=0)
|
||
fp, part = _paths(dl, info)
|
||
install(lambda a, u, kw: _FakeResponse([b'x' * 100]))
|
||
|
||
with pytest.raises(DownloadException) as ei:
|
||
dl.download_music_file(101, music_info=info)
|
||
|
||
assert '大小上限' in str(ei.value)
|
||
assert not part.exists() and not fp.exists(), '超限残片无续传价值，须清理'
|
||
|
||
|
||
# ============ 取消 ============
|
||
|
||
|
||
def test_cancel_before_transfer_clears_part_and_skips_network(env):
|
||
dl, _state, install = env
|
||
info = _info(size=20)
|
||
_fp, part = _paths(dl, info)
|
||
part.write_bytes(b'p' * 5)
|
||
cancel = threading.Event()
|
||
cancel.set()
|
||
session = install(lambda *a: pytest.fail('已取消不应发网络请求'))
|
||
|
||
with pytest.raises(DownloadCanceled):
|
||
dl.download_music_file(101, music_info=info, cancel_event=cancel)
|
||
|
||
assert session.calls == []
|
||
assert not part.exists(), '取消须清掉 .part'
|
||
|
||
|
||
def test_cancel_midway_clears_half_written_file(env):
|
||
dl, _state, install = env
|
||
info = _info(size=20)
|
||
fp, part = _paths(dl, info)
|
||
cancel = threading.Event()
|
||
|
||
def chunks():
|
||
yield b'a' * 5
|
||
cancel.set()
|
||
yield b'b' * 15
|
||
|
||
install(lambda a, u, kw: _FakeResponse(chunks()))
|
||
|
||
with pytest.raises(DownloadCanceled):
|
||
dl.download_music_file(101, music_info=info, cancel_event=cancel)
|
||
|
||
assert not part.exists() and not fp.exists()
|
||
|
||
|
||
def test_network_error_while_canceled_reports_canceled(env):
|
||
dl, _state, install = env
|
||
info = _info(size=20)
|
||
fp, part = _paths(dl, info)
|
||
cancel = threading.Event()
|
||
|
||
def chunks():
|
||
yield b'a' * 5
|
||
cancel.set()
|
||
raise OSError('句柄异常')
|
||
|
||
install(lambda a, u, kw: _FakeResponse(chunks()))
|
||
|
||
with pytest.raises(DownloadCanceled):
|
||
dl.download_music_file(101, music_info=info, cancel_event=cancel, retries=2)
|
||
|
||
assert not part.exists() and not fp.exists(), '已取消时残片没有续传价值'
|
||
|
||
|
||
def test_cancel_after_promote_keeps_file_but_skips_metadata(env):
|
||
dl, state, install = env
|
||
info = _info(size=20)
|
||
fp, part = _paths(dl, info)
|
||
cancel = threading.Event()
|
||
|
||
def cb(written, _total):
|
||
if written >= 20:
|
||
cancel.set()
|
||
|
||
install(_body(20))
|
||
|
||
with pytest.raises(DownloadCanceled):
|
||
dl.download_music_file(101, music_info=info, cancel_event=cancel,
|
||
progress_cb=cb)
|
||
|
||
assert fp.exists() and not part.exists(), '已转正的文件不回滚'
|
||
assert state['meta'] == [], '取消后不应再写元数据'
|
||
|
||
|
||
# ============ 元数据 ============
|
||
|
||
|
||
def test_metadata_written_only_when_requested(env):
|
||
dl, state, install = env
|
||
install(_body(20))
|
||
|
||
dl.download_music_file(101, music_info=_info(mid=101), write_meta=False)
|
||
assert state['meta'] == [], 'write_meta=False 不应写元数据'
|
||
|
||
r = dl.download_music_file(102, music_info=_info(mid=102), write_meta=True,
|
||
meta_fields=['title'])
|
||
assert r.success
|
||
assert [f for _p, f in state['meta']] == [['title']], 'fields 应原样透传'
|