fetchtorrent: add flatten argument for rqbit (#432330)

- `tooling-language-server` has been renamed to `deputy` (both the package and binary), following the rename of the upstream project.

- `fetchtorrent`, when using the "rqbit" backend, erroneously started fetching files into a subdirectory in Nixpkgs 24.11.  The original behaviour – which matches the behaviour using the "transmission" backend – has now been restored.  Users reliant on the erroneous behaviour can temporarily maintain it by adding `flatten = false` to the `fetchtorrent` arguments; Nix will produce an evaluation warning for anyone using `backend = "rqbit"` without `flatten = true`.

- `webfontkitgenerator` has been renamed to `webfont-bundler`, following the rename of the upstream project.

  The binary name remains `webfontkitgenerator`.

  The `webfontkitgenerator` package is an alias to `webfont-bundler`.

      "bittorrent"

    else

      "bittorrent-" + builtins.head (builtins.match urlRegexp url),

  config ?

    if (backend == "transmission") then

      { }

    else

      throw "json config for configuring fetchFromBitorrent only works with the transmission backend",

  config ? { },

  hash,

  backend ? "transmission",

  recursiveHash ? true,

  flatten ? null,

  postFetch ? "",

  postUnpack ? "",

  meta ? { },

}:

let

  afterSuccess = writeShellScript "fetch-bittorrent-done.sh" ''

  # Default to flattening if no flatten argument was specified.

  flatten' = if flatten == null then true else flatten;

  transmissionFinishScript = writeShellScript "fetch-bittorrent-done.sh" ''

    ${postUnpack}

    # Flatten the directory, so that only the torrent contents are in $out, not

    # the folder name

    kill $PPID

  '';

  jsonConfig = (formats.json { }).generate "jsonConfig" config;

  # https://github.com/NixOS/nixpkgs/issues/432001

  #

  # For a while, the transmission backend would put the downloaded torrent in

  # the output directory, but whether the rqbit backend would put the output in

  # the output directory or a subdirectory depended on the version of rqbit.

  # We want to standardise on a single behaviour, but give users of

  # fetchtorrent with the rqbit backend some warning that the behaviour might

  # be unexpected, particularly since we can't know what behaviour users might

  # be expecting at this point, and they probably wouldn't notice a change

  # straight away because the results are fixed-output derivations.

  #

  # This warning was introduced for 25.11, so we can remove handling of the

  # `flatten` argument once that release is no longer supported.

  warnings =

    if backend == "rqbit" && flatten == null then

      [

        ''

          `fetchtorrent` with the rqbit backend may or may not have the

          downloaded files stored in a subdirectory of the output directory.

          Verify which behaviour you need, and set the `flatten` argument to

          `fetchtorrent` accordingly.

          The `flatten = false` behaviour will still produce a warning, as this

          behaviour is deprecated.  It is only available with the "rqbit" backend

          to provide temporary support for users who are relying on the

          previous incorrect behaviour.  For a warning-free evaluation, use

          `flatten = true`.

        ''

      ]

    else if flatten == false then

      [

        ''

          `fetchtorrent` with `flatten = false` is deprecated and will be

          removed in a future release.

        ''

      ]

    else

      [ ];

in

assert lib.assertMsg (config != { } -> backend == "transmission") ''

  json config for configuring fetchtorrent only works with the transmission backend

'';

assert lib.assertMsg (backend == "transmission" -> flatten') ''

  `flatten = false` is only supported by the rqbit backend for fetchtorrent

'';

runCommand name

  {

    inherit meta;

        mkdir -p $downloadedDirectory

        mkdir -p $HOME/.config/transmission

        cp ${jsonConfig} $HOME/.config/transmission/settings.json

        port="$(shuf -n 1 -i 49152-65535)"

        function handleChild {

          # This detects failures and logs the contents of the transmission fetch

          find $out

          exit 0

        }

        trap handleChild CHLD

        transmission-cli --port $(shuf -n 1 -i 49152-65535) --portmap --finish ${afterSuccess} --download-dir $downloadedDirectory --config-dir "$HOME"/.config/transmission "$url"

        transmission-cli \

            --port "$port" \

            --portmap \

            --finish ${transmissionFinishScript} \

            --download-dir "$downloadedDirectory" \

            --config-dir "$HOME"/.config/transmission \

            "$url"

      ''

    else

      ''

        export HOME=$TMP

        rqbit --disable-dht-persistence --http-api-listen-addr "127.0.0.1:$(shuf -n 1 -i 49152-65535)" download -o $out --exit-on-finish "$url"

      ''

      + lib.optionalString flatten' ''

        downloadedDirectory=$out/downloadedDirectory

        mkdir -p $downloadedDirectory

      ''

      + lib.optionalString (!flatten') ''

        downloadedDirectory=$out

      ''

      + ''

        port="$(shuf -n 1 -i 49152-65535)"

        rqbit \

            --disable-dht-persistence \

            --http-api-listen-addr "127.0.0.1:$port" \

            download \

            -o "$downloadedDirectory" \

            --exit-on-finish \

            "$url"

        ${postUnpack}

      ''

      + lib.optionalString flatten' ''

        # Flatten the directory, so that only the torrent contents are in $out,

        # not the folder name

        shopt -s dotglob

        mv -v $downloadedDirectory/*/* $out

        rm -v -rf $downloadedDirectory

        unset downloadedDirectory

      ''

      + ''

        ${postFetch}

      ''

  )

  };

  # Via https://webtorrent.io/free-torrents

  httpUrl = "https://webtorrent.io/torrents/sintel.torrent";

  magnetUrl = "magnet:?xt=urn:btih:08ada5a7a6183aae1e09d831df6748d566095a10&dn=Sintel&tr=udp%3A%2F%2Fexplodie.org%3A6969&tr=udp%3A%2F%2Ftracker.coppersurfer.tk%3A6969&tr=udp%3A%2F%2Ftracker.empire-js.us%3A1337&tr=udp%3A%2F%2Ftracker.leechers-paradise.org%3A6969&tr=udp%3A%2F%2Ftracker.opentrackr.org%3A1337&tr=wss%3A%2F%2Ftracker.btorrent.xyz&tr=wss%3A%2F%2Ftracker.fastcast.nz&tr=wss%3A%2F%2Ftracker.openwebtorrent.com&ws=https%3A%2F%2Fwebtorrent.io%2Ftorrents%2F&xs=https%3A%2F%2Fwebtorrent.io%2Ftorrents%2Fsintel.torrent";

  http.url = "https://webtorrent.io/torrents/sintel.torrent";

  magnet.url = "magnet:?xt=urn:btih:08ada5a7a6183aae1e09d831df6748d566095a10&dn=Sintel&tr=udp%3A%2F%2Fexplodie.org%3A6969&tr=udp%3A%2F%2Ftracker.coppersurfer.tk%3A6969&tr=udp%3A%2F%2Ftracker.empire-js.us%3A1337&tr=udp%3A%2F%2Ftracker.leechers-paradise.org%3A6969&tr=udp%3A%2F%2Ftracker.opentrackr.org%3A1337&tr=wss%3A%2F%2Ftracker.btorrent.xyz&tr=wss%3A%2F%2Ftracker.fastcast.nz&tr=wss%3A%2F%2Ftracker.openwebtorrent.com&ws=https%3A%2F%2Fwebtorrent.io%2Ftorrents%2F&xs=https%3A%2F%2Fwebtorrent.io%2Ftorrents%2Fsintel.torrent";

  # All routes to download the torrent should produce the same output and

  # therefore have the same FOD hash.

  hash = "sha256-EzbmBiTEWOlFUNaV5R4eDeD9EBbp6d93rfby88ACg0s=";

  flattened.hash = "sha256-EzbmBiTEWOlFUNaV5R4eDeD9EBbp6d93rfby88ACg0s=";

  unflattened.hash = "sha256-lVrlo1AwmFcxwsIsY976VYqb3hAprFH1xWYdmlTuw0U=";

in

{

  http-link = testers.invalidateFetcherByDrvHash fetchtorrent {

    inherit hash;

    url = httpUrl;

# Seems almost but not quite worth using lib.mapCartesianProduct...

builtins.mapAttrs (n: v: testers.invalidateFetcherByDrvHash fetchtorrent v) {

  http-link = {

    inherit (http) url;

    inherit (flattened) hash;

    inherit (sintel) meta;

  };

  http-link-transmission = {

    inherit (http) url;

    backend = "transmission";

    inherit (flattened) hash;

    inherit (sintel) meta;

  };

  magnet-link = testers.invalidateFetcherByDrvHash fetchtorrent {

    inherit hash;

    url = magnetUrl;

  magnet-link = {

    inherit (magnet) url;

    inherit (flattened) hash;

    inherit (sintel) meta;

  };

  magnet-link-transmission = {

    inherit (magnet) url;

    backend = "transmission";

    inherit (flattened) hash;

    inherit (sintel) meta;

  };

  http-link-rqbit = {

    inherit (http) url;

    backend = "rqbit";

    inherit (flattened) hash;

    inherit (sintel) meta;

  };

  http-link-rqbit = testers.invalidateFetcherByDrvHash fetchtorrent {

    inherit hash;

    url = httpUrl;

  magnet-link-rqbit = {

    inherit (magnet) url;

    backend = "rqbit";

    meta = sintel.meta // {

      broken = true;

    inherit (flattened) hash;

    inherit (sintel) meta;

  };

  http-link-rqbit-flattened = {

    inherit (http) url;

    backend = "rqbit";

    flatten = true;

    inherit (flattened) hash;

    inherit (sintel) meta;

  };

  magnet-link-rqbit = testers.invalidateFetcherByDrvHash fetchtorrent {

    inherit hash;

    url = magnetUrl;

  magnet-link-rqbit-flattened = {

    inherit (magnet) url;

    backend = "rqbit";

    meta = sintel.meta // {

      broken = true;

    flatten = true;

    inherit (flattened) hash;

    inherit (sintel) meta;

  };

  http-link-rqbit-unflattened = {

    inherit (http) url;

    backend = "rqbit";

    flatten = false;

    inherit (unflattened) hash;

    inherit (sintel) meta;

  };

  magnet-link-rqbit-unflattened = {

    inherit (magnet) url;

    backend = "rqbit";

    flatten = false;

    inherit (unflattened) hash;

    inherit (sintel) meta;

  };

}