The distinction between the inputs doesn't really make sense in the
mkShell context. Technically speaking, we should be using the
nativeBuildInputs most of the time.
So in order to make this function more beginner-friendly, add "packages"
as an attribute, that maps to nativeBuildInputs.
This commit also updates all the uses in nixpkgs.
mergeInputs is now simply defined in terms of `concatLists` and
`catAttrs` instead of a more complicated `foldr`.
Note that the order of PATH has also changed. For example running the
following with nix-shell:
let
pkgs = import <nixpkgs> {};
shell1 = pkgs.mkShell {
buildInputs = [ pkgs.htop ];
};
shell2 = pkgs.mkShell {
buildInputs = [ pkgs.hello ];
};
shell3 = pkgs.mkShell {
inputsFrom = [ shell1 shell2 ];
buildInputs = [ pkgs.tree ];
};
in shell3
Results in the following PATH:
$ echo $PATH
...
/nix/store/yifq4bikf7m07160bpia7z48ciqddbfi-tree-1.8.0/bin:
/nix/store/vhxqk81234ivqw1a7j200a1c69k8mywi-htop-2.2.0/bin:
/nix/store/n9vm3m58y1n3rg3mlll17wanc9hln58k-hello-2.10/bin
...
Previously the order was:
/nix/store/n9vm3m58y1n3rg3mlll17wanc9hln58k-hello-2.10/bin
/nix/store/vhxqk81234ivqw1a7j200a1c69k8mywi-htop-2.2.0/bin:
/nix/store/yifq4bikf7m07160bpia7z48ciqddbfi-tree-1.8.0/bin:
I think the new order makes more sense because it allows to override
the PATH in the outermost mkShell.
Running the following expression with nix-shell:
let
pkgs = import <nixpkgs> {};
shell1 = pkgs.mkShell {
shellHook = ''
echo shell1
'';
};
shell2 = pkgs.mkShell {
shellHook = ''
echo shell2
'';
};
shell3 = pkgs.mkShell {
inputsFrom = [ shell1 shell2 ];
shellHook = ''
echo shell3
'';
};
in shell3
Will now results in:
shell2
shell1
shell3
Note that packages in the front of inputsFrom have precedence over
packages in the back. The outermost mkShell has precedence over all.
