[darwin] rustPlatform.buildRustPackage: do not add libiconv to buildInputs

[danieldk]

Motivation for this change

Many buildRustPackage-based derivations require libiconv as a build
input on Darwin. This is caused by libc unconditionally linking
against libiconv. However, this was recently changed:

rust-lang/libc#2150

We will probably see this dependency disappear over the coming months
once a new libc crate version is released and other crates adopt
this new version.

Since this is already an optional dependency and it will disappear
in the coming time, we should probably not unconditionally add it
to all Rust crates.

Can't test, because I don't have a Darwin machine.

cc @jonringer

Things done

• Tested using sandboxing (nix.useSandbox on NixOS, or option sandbox in nix.conf on non-NixOS linux)
• Built on platform(s)
  • NixOS
  • macOS
  • other Linux distributions
• Tested via one or more NixOS test(s) if existing and applicable for the change (look inside nixos/tests)
• Tested compilation of all pkgs that depend on this change using nix-shell -p nixpkgs-review --run "nixpkgs-review wip"
• Tested execution of all binary files (usually in ./result/bin/)
• Determined the impact on package closure size (by running nix path-info -S before and after)
• Ensured that relevant documentation is up to date
• Fits CONTRIBUTING.md.

[prusnak]

libiconv needs to be reintroduced to pkgs/development/compilers/rust/cargo.nix again, because 252bf94 removed it

[prusnak]

Shall we switch this to draft so it's not accidentally merged before libc crate is updated to 0.2.95 which fixes the iconv issue?

[rmcgibbo]

I can try testing this on darwin -- do you have a particular subset set of packages to test that you know are relevant? FWIW I've been using https://github.com/jtojnar/nixpkgs-fastmac, in addition to the mac in my closet. It seems to work pretty well.

[danieldk]

Shall we switch this to draft so it's not accidentally merged before libc crate is updated to 0.2.95 which fixes the iconv issue?

But we can’t switch wholesale to 0.2.95 once it is out, we have to rely on the various upstream crates to update their lock files.

It’s really a dependency that should be tracked per derivation.

But I am fine with making this a draft. Then we have this workaround for the 21.05 release and can remove it later.

edit: seems like cannot make this a draft on my phone. Feel free to convert it!

[jonringer]

thanks for starting a new PR :)

[danieldk]

0.2.95 was released two weeks ago, so taking this PR out of draft.

https://github.com/rust-lang/libc/releases/tag/0.2.95

This is the first version that does not unconditionally link libiconv on darwin.

Of course, downstream crates have to update to this version of the libc crate, but the number of crates requiring iconv on darwin should shrink drastically over time. For those that need it, we should have this dependency in their buildInputs, rather than having this in the buildInputs of every buildRustPackage derivation.

[Profpatsch]

rustPackages is currently broken on 21.05 because libiconv was removed. Can we please introduce it again?

[danieldk]

rustPackages is currently broken on 21.05 because libiconv was removed. Can we please introduce it again?

Seems to be there in 21.05?

nixpkgs/pkgs/build-support/rust/default.nix

Line 122 in 6613a30

++ lib.optionals stdenv.hostPlatform.isDarwin [ libiconv ]

[Profpatsch]

Seems to be there in 21.05?

lorri still breaks as far as I can see: https://github.com/nix-community/lorri/pull/71/checks?check_run_id=3812404819

[danieldk]

Seems to be there in 21.05?

lorri still breaks as far as I can see: https://github.com/nix-community/lorri/pull/71/checks?check_run_id=3812404819

From a quick look, lorri seems to use Carnix? Carnix doesn't use buildRustPackage, but buildRusetCrate, so an override needs to be added to

https://github.com/NixOS/nixpkgs/blob/master/pkgs/build-support/rust/default-crate-overrides.nix

for the libc crate.

[Profpatsch]

From a quick look, lorri seems to use Carnix? Carnix doesn't use buildRustPackage, but buildRusetCrate, so an override needs to be added to

The PR I linked actually switches it over to crate2nix since carnix is super out of date at this point and failed with the newer lock file format.

[danieldk]

From a quick look, lorri seems to use Carnix? Carnix doesn't use buildRustPackage, but buildRusetCrate, so an override needs to be added to

The PR I linked actually switches it over to crate2nix since carnix is super out of date at this point and failed with the newer lock file format.

crate2nix also uses buildRustCrate.

[Profpatsch]

tbh I stopped caring about Darwin and call upon @NixOS/darwin-maintainers

[Profpatsch]

I mean this has been broken since May or even earlier, and is exactly why NixOS/rfcs#112 exists.

[domenkozar]

@Profpatsch I'd kindly ask you to be less hateful and show some empathy for others.

[winterqt]

This is still required. I tried to figure out why this happens a few months ago, but I only got a little info (it's an upstream issue, to my knowledge). I'll try to pick it back up though.

[winterqt]

(and by "this" I mean that libiconv still needs to be present)

[uri-canva]

For anyone else having issues with buildRustCrate, crate2nix or carnix and ending up here, the fix is in nixpkgs master: c9f0c6f.

[Profpatsch]

@Profpatsch I'd kindly ask you to be less hateful and show some empathy for others.

apathy ≠ hate