send_file() 与 send_from_directory()

  GET /file   → 200 Content-Type: text/plain; charset=utf-8 | Content-Length: 17 | Content-Disposition: inline; filename=report.txt | Cache-Control: no-cache | ETag: "1790911494.4854403-17-820325724" | Last-Modified: Fri, 02 Oct 2026 03:24:54 GMT
  GET /abs    → 200 Content-Type: text/plain; charset=utf-8 | Content-Length: 17 | Content-Disposition: inline; filename=report.txt | Cache-Control: no-cache | ETag: "1790911494.4854403-17-820325724" | Last-Modified: Fri, 02 Oct 2026 03:24:54 GMT
  GET /dl     → 200 Content-Type: text/plain; charset=utf-8 | Content-Length: 17 | Content-Disposition: attachment; filename=report.txt | Cache-Control: no-cache | ETag: "1790911494.4854403-17-820325724" | Last-Modified: Fri, 02 Oct 2026 03:24:54 GMT
  GET /dl-cn  → 200 Content-Type: text/plain; charset=utf-8 | Content-Length: 17 | Content-Disposition: attachment; filename=" (1).txt"; filename*=UTF-8''%E6%9C%88%E5%BA%A6%20%E6%8A%A5%E5%91%8A%281%29.txt | Cache-Control: no-cache | ETag: "1790911494.4854403-17-820325724" | Last-Modified: Fri, 02 Oct 2026 03:24:54 GMT

  GET /mem      → 200 Content-Type: text/plain; charset=utf-8 | Content-Disposition: inline; filename=m.txt | Content-Length: 9
  GET /mem-bad  → 500 Content-Type: text/html; charset=utf-8 | Content-Length: 265
  GET /mem-name → 200 Content-Type: text/csv; charset=utf-8 | Content-Disposition: inline; filename=export.csv | Content-Length: 8
  直接调用 /mem-bad 的视图 → TypeError: Unable to detect the MIME type because a file name is not available. Either set 'download_name', pass a path instead of a file, or set 'mimetype'.

  GET /age      → 200 Cache-Control: public, max-age=3600 | ETag: "1790911494.4854403-17-820325724" | Last-Modified: Fri, 02 Oct 2026 03:24:54 GMT | Expires: Fri, 02 Oct 2026 04:24:54 GMT
  GET /nocache  → 200 Cache-Control: no-cache, max-age=0 | Last-Modified: Fri, 02 Oct 2026 03:24:54 GMT | Expires: Fri, 02 Oct 2026 03:24:54 GMT
  GET /nocond   → 200 Cache-Control: no-cache | ETag: "1790911494.4854403-17-820325724" | Last-Modified: Fri, 02 Oct 2026 03:24:54 GMT
  带 If-None-Match → 304 | 正文 0 字节
  conditional=False 的路由带 If-None-Match → 200

  GET /dir/report.txt              → 200
  GET /dir/../secret.txt           → 404
  GET /dir/..%2fsecret.txt         → 404
  GET /dir/%2e%2e/secret.txt       → 404
  GET /dir//etc/passwd             → 308
  GET /dir/sub/../report.txt       → 200
  GET /dir/nope.txt                → 404
  GET /dir-rel/report.txt          → 200
  找不到文件 send_file("data/nope.txt") → 视图里抛出 FileNotFoundError → 经过 HTTP 是 500
  找不到文件 send_from_directory(目录, "nope.txt") → NotFound → HTTP 404

  report.txt       → text/plain; charset=utf-8
  pic.png          → image/png
  page.html        → text/html; charset=utf-8
  note.md          → text/markdown; charset=utf-8
  data.json        → application/json
  archive.tar.gz   → application/x-tar
  noext            → application/octet-stream
  script.js        → text/javascript; charset=utf-8
  覆盖 mimetype="application/x-custom" → application/x-custom

  USE_X_SENDFILE=True → 状态 200 | X-Sendfile = <项目>/data/report.txt | 正文长度 0

  gunicorn 下 wsgi.file_wrapper = {"file_wrapper":"<class 'gunicorn.http.wsgi.FileWrapper'>"}
  send_file                峰值 RSS ≈ 35 MiB(基线 35 MiB)| curl:314572800 字节 0.065262s
  open().read() 整个读进内存     峰值 RSS ≈ 335 MiB(基线 35 MiB)| curl:314572800 字节 0.105458s