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nixpkgs/pkgs/build-support/mkshell/default.nix
Jonas Chevalier 1e910209ae
mkShell: make it buildable (#153194)
When I designed `mkShell`, I didn't have a good idea of what the output
should look like and so decided to make the build fail. In practice,
this causes quite a bit of confusion and complications because now the
shell cannot be part of a normal package set without failing the CI as
well.

This commit changes that build phase to record all the build inputs in a
file. That way it becomes possible to build it, makes sure that all the
build inputs get built as well, and also can be used as a GC root.
(by applying the same trick as #95536).

The documentation has also been improved to better describe what mkShell
does and how to use it.
2022-01-08 01:54:04 +01:00

56 lines
1.6 KiB
Nix

{ lib, stdenv, buildEnv }:
# A special kind of derivation that is only meant to be consumed by the
# nix-shell.
{ name ? "nix-shell"
, # a list of packages to add to the shell environment
packages ? [ ]
, # propagate all the inputs from the given derivations
inputsFrom ? [ ]
, buildInputs ? [ ]
, nativeBuildInputs ? [ ]
, propagatedBuildInputs ? [ ]
, propagatedNativeBuildInputs ? [ ]
, ...
}@attrs:
let
mergeInputs = name:
(attrs.${name} or [ ]) ++
(lib.subtractLists inputsFrom (lib.flatten (lib.catAttrs name inputsFrom)));
rest = builtins.removeAttrs attrs [
"name"
"packages"
"inputsFrom"
"buildInputs"
"nativeBuildInputs"
"propagatedBuildInputs"
"propagatedNativeBuildInputs"
"shellHook"
];
in
stdenv.mkDerivation ({
inherit name;
buildInputs = mergeInputs "buildInputs";
nativeBuildInputs = packages ++ (mergeInputs "nativeBuildInputs");
propagatedBuildInputs = mergeInputs "propagatedBuildInputs";
propagatedNativeBuildInputs = mergeInputs "propagatedNativeBuildInputs";
shellHook = lib.concatStringsSep "\n" (lib.catAttrs "shellHook"
(lib.reverseList inputsFrom ++ [ attrs ]));
phases = [ "buildPhase" ];
buildPhase = ''
echo "------------------------------------------------------------" >>$out
echo " WARNING: the existence of this path is not guaranteed." >>$out
echo " It is an internal implementation detail for pkgs.mkShell." >>$out
echo "------------------------------------------------------------" >>$out
echo >> $out
# Record all build inputs as runtime dependencies
export >> $out
'';
} // rest)