NixOS/nix

fetchTree: use last-modified HTTP header where possible

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#9,067 建立於 2023年9月29日

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featurefetchinggood first issue

描述

Is your feature request related to a problem? Please describe.

Currently fetchTree with type=tarball+http(s) gets lastModified from the mtime of the tarball contents. Some formats such as zip do not include this metadata, so lastModified ends up being incorrectly set to the current time.

type=file+http(s) does not set lastModified at all.

Describe the solution you'd like

Most webservers, when serving static files, will send a last-modified header set to the mtime of the served file. We could set lastModified to this value, or use it as fallback when mtime of contents is absent.

Describe alternatives you've considered

Do not set lastModified when mtime metadata is not present in archives. This should probably be done anyway when neither mtime nor last-modified is present.

Additional context

Priorities

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貢獻者指南

技術棧
cpp
領域
backendcli
議題類型
feature
難度面向新貢獻者的預計實作難度，1 表示很小改動，5 表示專家級工作。
3
預計時間有經驗貢獻者完成調查、實作、測試並準備 pull request 的粗略時間範圍。
1-3 hours
活動狀態議題目前的可參與程度：新鮮、活躍、陳舊、阻塞或等待維護者輸入。
fresh
清晰度議題是否清楚說明預期改動、驗收標準和下一步。
clear
前置要求
C++HTTP basicsNix source structure
新手友善度1-100 的估計分數，表示該議題對首次貢獻者的友善程度。
50
研究方向
Investigate the fetchTree implementation in src/libfetchers/ (likely tarball.cc and file.cc). Look for how lastModified is currently set and where HTTP headers are available. Check if the HTTP response already passes headers; if not, modify the fetcher to parse the last modified header and use it as fallback when other mtime is absent. Consider edge cases where the header is missing or invalid.