nix-shell documentation

[pelasgus]

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+ reuse lint
# MISSING COPYRIGHT AND LICENSING INFORMATION

The following files have no copyright and licensing information:
* ../nix-shell/rust_contributor_shell.nix
* ../nix-shell/rust_user_shell.nix

# SUMMARY

* Bad licenses:
---
* Read errors: 0
* Files with copyright information: 43569 / 43571
* Files with license information: 43569 / 43571

Unfortunately, your project is not compliant with version 3.0 of the REUSE Specification :-(
  network time: Tue, 26 Sep 2023 22:02:58 GMT
##[error]Process completed with exit code 1.
Post job cleanup.

[Noratrieb]

We already have a nix shell in the dev guide to copy and adjust as liked
https://rustc-dev-guide.rust-lang.org/building/suggested.html#using-nix-shell

I'm not sure whether it's worth it to keep one in the repo (if we do, then it should definitely go into src/etc instead of a top level directory) but I think it's better to just link to the dev guide instead.

[Mark-Simulacrum]

I don't think we should keep two copies of this, and rustc-dev-guide seems like the better place to me. I'm happy to merge a PR pointing to the dev guide for Nix specifically if we don't have that yet.

[Dylan-DPC]

@pelasgus any updates?

[bors]

☔ The latest upstream changes (presumably #119945) made this pull request unmergeable. Please resolve the merge conflicts.

[Dylan-DPC]

Closing this as it's better to have this in one place and has been inactive for a while

[futile]

Just spent quite some time (read: hours) creating my own nix-shell (well, a flake.nix) for rustc development, before I found the one in the docs 🙃. There are some non-obvious parts, and it's hard to know that you got it right, even if it works for what you're testing.

I tried searching for *.nix files in the repo before, but didn't see any, and also didn't find the relevant docs page while googling. It seems the magic google incantation needs to contain rustc dev nix-shell, just rustc dev nix or rustc nix-shell is not enough. And even then it's not the first result, but it can be found.

Also, nowadays Nix flakes are used a lot, where the file is then called flake.nix, and googling for rustc dev flake or rustc devShell (devShell is the name used in flake.nix) doesn't turn up any (helpful) links either, especially not the one in the rustc dev guide.

So I think discoverability would really benefit from adding an (example) nix-shell to the source tree, e.g., in src/etc/nix/{flake.nix,shell.nix}. These two (new and old Nix shell formats) can be made compatible, i.e., without having to repeat the configuration.

Some other way of increasing discoverability would also be ok, but I think just adding it as a file, even just shell.nix, ignoring flake.nix for now, would be a massive help.

Posted here since the discussion seemed related/relevant, let me know if I should open a new issue/PR instead! Cheers & thanks! :)

[pelasgus]

@Dylan-DPC please forgive my tardiness. Please do re-open, I will provide new declarative shells for both nix(shell & flake) and guix, contribute them to the docs and then restructure the readme so they link here.