Nix boost install misses headers

Question

I installed boost using the nix package manager by $ nix-env -i boost, but there are no boost headers in current generation of my profile.

Thus ~/.nix-profile/include/boost does not exit, but the boost library files can be found in ~/.nix-profile/lib.

I searched in the nix store and found the headers in boost-dev folders within the store.

Why doesn`t nix link the boost headers into my current generation?

Answer 1

The boost package is a split package, so it has multiple outputs.

$ nix-instantiate --eval -E '(import <nixpkgs> {}).boost.outputs'
[ "out" "dev" ]

In this case the out output has the libraries, and the dev output has the headers. Normally the dev output is not installed to the user environment when you use nix-env -i. But it is used internally when the package is a build dependency of another package.

You can see what outputs will be installed like this:

$ nix-instantiate --eval -E 'builtins.toString (import <nixpkgs> {}).boost.meta.outputsToInstall'
"out"

The documentation indicates that you can override meta.outputsToInstall if you want other outputs.

My best attempt at doing this is:

nix-env -i -E \
  '_: with import <nixpkgs> {};' \
  'let newmeta = ( boost.meta // { outputsToInstall = ["out" "dev"]; } );' \
  'in boost // { meta = newmeta; }'

Would be interested to hear of a less cumbersome version...

I suspect the real answer is that we shouldn't be trying to install development stuff into the user environment. Perhaps it's better to write a default.nix file which defines development dependencies, and instantiate it with nix-shell. See for example https://garbas.si/2015/reproducible-development-environments.html.