@GrahamcOfBorg eval

I think this should be brought up on the mailing list.

This will regress closure sizes since now anything in systemPackages will install the dev outputs and other pointless stuff.

Regarding #44144, compiling outside nix-shell isn't really supported anyway.

As for having manpages installed by nix-env, I think nix-env should call into Nixpkgs buildEnv (or some new dedicated custom function) to decide what outputs to install. That way you could e.g. disable installation of manpages or info pages based on ~/.nixpkgs/.config.nix.

This will regress closure sizes since now anything in systemPackages will install the dev outputs and other pointless stuff.

Doesn't systemPackages use pathsToLink though? I'd bet there is some increase in size but not a huge amount. We can definitely provide a global outputsToInstall in buildEnv that the NixOS environment can set to [ "out" ] or something else for this.

As for having manpages installed by nix-env, I think nix-env should call into Nixpkgs buildEnv (or some new dedicated custom function) to decide what outputs to install. That way you could e.g. disable installation of manpages or info pages based on ~/.nixpkgs/.config.nix.

Yes, I think for most of us this would be the ideal solution. I still think we would want the default behavior of that function to be install everything. Most beginners to Nix will not understand multiple outputs, or pathsToLink, etc. They will just assume Nix(pkgs) does not provide info pages, man pages, headers, libraries, etc. I want to make sure we can still provide good support for the imperative package installation style, even if most NixOS/Nixpkgs core contributors are using something else.

@GrahamcOfBorg eval

Doesn't systemPackages use pathsToLink though?

It uses buildEnv does respect outputsToInstall.

I'd bet there is some increase in size but not a huge amount.

No, it's going to be hundreds of megs if some package's .dev pulls in GCC or glibc headers et al.

I want to make sure we can still provide good support for the imperative package installation style,

For development nearly nothing currently supports that since setup hooks won't be run. And most likely isn't going to be fixed without a major redesign.

For development nearly nothing currently supports that since setup hooks won't be run. And most likely isn't going to be fixed without a major redesign.

This doesn't just apply to headers & libraries. Things like man pages are now frequently missing when someone decides to add a separate output for it. Not everyone is installing their packages through systemPackages. I think it's a bad idea to expect everyone to be doing this, especially when it only is possible when you have root privileges, or have set up something else like home-manager.

I have added a commit to restore the buildEnv behavior. I agree that it makes sense to only use one output in buildEnv's case because it can be configured to add more outputs by the user. nix-env provides no equivalent configuration, however.

Ah, cross-link: 3342f71#commitcomment-29875048

If we need to do this without any changes to nix-env we could perhaps retcon outputsToInstall to make it only apply to nix-env (i.e. replace all other usages of that in nixpkgs with say, propagatedUserEnvPackages except the one in mk-derivation that sets it). But #44168 (comment) is still more preferable.

If we need to do this without any changes to nix-env we could perhaps retcon outputsToInstall to make it only apply to nix-env (i.e. replace all other usages of that in nixpkgs with say, propagatedUserEnvPackages except the one in mk-derivation that sets it).

s/propagatedUserEnvPackages/propagatedUserEnvPkgs/

The only usage I found was in buildenv.pl. I would be interested in whether there are any others. Do you think it makes sense to leave the outputsToInstall uses in packages the same?

But #44168 (comment) is still more preferable.

It's definitely preferable, but could take a long time. The goal for me is to find some solution for #24717 before 18.09 release. If someone wants to step up and create a PR to Nix to use a custom buildEnv, that would be great but I am not counting on it.

Because @vcunat is assigned #24717, I kind of want to see what he thinks of this PR. After the update to have buildEnv calculate outputsToInstall itself, I am hoping it addresses some concerns. This whole thing has been an outstanding issue for too long IMO. I definitely get that things like dev don't really belong in the profile, but it doesn't seem to hurt too much either if they are (in fact they are downloaded anyway).

I haven't noticed extraneous (unused) outputs being downloaded; that would be a bug. (Unless e.g. the usual case that .bin is installed and it depends on .out, but that's basically intentional. I meant mainly .dev, i.e. the main motivator behind splitting.)

Closing in favor of #35884 for now.