nixpkgs/pkgs/build-support/fetchdarcs/builder.sh
Maximilian Bosch 8bc5104a6e
treewide: refactor .attrs.sh detection
When specifying the `builder` attribute in `stdenv.mkDerivation`, this
will be effectively transformed into

    builtins.derivation {
      builder = stdenv.shell;
      args = [ "-e" builder ];
    }

This also means that `default-builder.sh` is never sourced and as a
result it's not guaranteed that `$NIX_ATTRS_SH_FILE` is set to a correct
location[1].

Also, we need to source `.attrs.sh` to source `$stdenv`. So, the
following is done now:

* If `$NIX_ATTRS_SH_FILE` points to a correct location, then use it.
  Directly using `.attrs.sh` is problematic for `nix-shell(1)` usage
  (see previous commit for more context), so prefer the environment
  variable if possible.

* Otherwise, if `.attrs.sh` exists, then use it. See [1] for when this
  can happen.

* If neither applies, it can be assumed that `__structuredAttrs` is
  turned off and thus nothing needs to be done.

[1] It's possible that it doesn't exist at all - in case of Nix 2.3 or
    it can point to a wrong location on older Nix versions with a bug in
    `__structuredAttrs`.
2023-10-04 18:36:57 +02:00

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if [ -e "$NIX_ATTRS_SH_FILE" ]; then . "$NIX_ATTRS_SH_FILE"; elif [ -f .attrs.sh ]; then . .attrs.sh; fi
source $stdenv/setup
tagtext=""
tagflags=""
# Darcs hashes are sha1 (120 bits, 40-character hex)
if [[ "$rev" =~ [a-fA-F0-9]{40} ]]; then
tagtext="(hash $rev)"
tagflags="--to-hash=$rev"
elif test -n "$rev"; then
tagtext="(tag $rev)"
tagflags="--tag=$rev"
elif test -n "$context"; then
tagtext="(context)"
tagflags="--context=$context"
fi
echo "getting $url $partial ${tagtext} into $out"
darcs get --lazy $tagflags "$url" "$out"
# remove metadata, because it can change
rm -rf "$out/_darcs"