depot/third_party/nixpkgs/pkgs/build-support/compress-drv/default.nix

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{ lib, runCommand }:
/**
Compresses files of a given derivation, and returns a new derivation with
compressed files
# Inputs
`formats` ([String])
: List of file extensions to compress. Example: `["txt" "svg" "xml"]`.
`extraFindOperands` (String)
: Extra command line parameters to pass to the find command.
This can be used to exclude certain files.
For example: `-not -iregex ".*(\/apps\/.*\/l10n\/).*"`
`compressors` ( { ${fileExtension} :: String })
: Map a desired extension (e.g. `gz`) to a compress program.
The compressor program that will be executed to get the `COMPRESSOR` extension.
The program should have a single " {}", which will be the replaced with the
target filename.
Compressor must:
- read symlinks (thus --force is needed to gzip, zstd, xz).
- keep the original file in place (--keep).
# Type
```
compressDrv :: Derivation -> { formats :: [ String ]; compressors :: { ${fileExtension} :: String; } } -> Derivation
```
# Examples
:::{.example}
## `pkgs.compressDrv` usage example
```
compressDrv pkgs.spdx-license-list-data.json {
formats = ["json"];
compressors = {
gz = "${zopfli}/bin/zopfli --keep {}";
};
}
=>
«derivation /nix/store/...-spdx-license-list-data-3.24.0-compressed.drv»
```
See also pkgs.compressDrvWeb, which is a wrapper on top of compressDrv, for broader usage
examples.
:::
*/
drv:
{
formats,
compressors,
extraFindOperands ? "",
}:
let
validProg =
ext: prog:
let
matches = (builtins.length (builtins.split "\\{}" prog) - 1) / 2;
in
lib.assertMsg (
matches == 1
) "compressor ${ext} needs to have exactly one '{}', found ${builtins.toString matches}";
mkCmd =
ext: prog:
assert validProg ext prog;
''
find -L $out -type f -regextype posix-extended -iregex '.*\.(${formatsPipe})' ${extraFindOperands} -print0 \
| xargs -0 -P$NIX_BUILD_CORES -I{} ${prog}
'';
formatsPipe = lib.concatStringsSep "|" formats;
in
runCommand "${drv.name}-compressed"
(
(lib.optionalAttrs (drv ? pname) { inherit (drv) pname; })
// (lib.optionalAttrs (drv ? version) { inherit (drv) version; })
)
''
mkdir $out
# cannot use lndir here, because it stop recursing at symlinks that point to directories
(cd ${drv}; find -L -type d -exec mkdir -p $out/{} ';')
(cd ${drv}; find -L -type f -exec ln -s ${drv}/{} $out/{} ';')
${lib.concatStringsSep "\n\n" (lib.mapAttrsToList mkCmd compressors)}
''