Show installation instructions for flakes

[lilyball]

The installation instructions for a package list several different options for non-flakes usage, but it would be great if it could list the flake instructions.

For example, if I'm looking at jq-1.5, I'd like to see an example like

Run jq with nix run (requires flakes):

nix run NixOS/nixpkgs/a3962299f14944a0e9ccf8fd84bd7be524b74cd6#jq

[lilyball]

Turns out jq-1.5 was a bad example, that nixpkgs version is too old to have a flake.nix file. But the idea is still sound. Ideally the site would know if the nixpkgs version has a flake.nix and use that to affect the instructions (e.g. noting that there is no flake support for this version), but the simple approach of just including the instructions should work.

Also I guess with nix run specifically there's the potential for the package to not match the binary name (and not have the required meta key to handle that), so maybe it should offer nix shell instead 🤷🏻‍♀️

[lazamar]

Hey. Unfortunately I don't know much about flakes or what would be required to make it work, but feel free to make a PR and I'd be happy to review it.

[ostrolucky]

I think proper syntax is eg.

nix run nixpkgs/6d02a514db95d3179f001a5a204595f17b89cb32#kubectl -- version --sort

[lestephane]

I think proper syntax is eg.

nix run nixpkgs/6d02a514db95d3179f001a5a204595f17b89cb32#kubectl -- version --sort

this README shows a bunch or URL formats, I suppose nix run supports them all, but I have no way to check, as I'm still on 2.6.0.

[lestephane]

Hey. Unfortunately I don't know much about flakes or what would be required to make it work, but feel free to make a PR and I'd be happy to review it.

Here is an example of non-flake nixpkg I was able to turn into a flake, I found the commit id using your nix-versions page and a bit of search in the nixpgs repo history.

$ cat flake.nix
{
  description = "Duplicacy 2.7.2";

  inputs = {
    # https://github.com/NixOS/nixpkgs/commit/2a1fcb02eb8d8c589f851b49f4e8b59a0e2d2eec
    nixpkgs.url = "github:nixos/nixpkgs/2a1fcb02eb8d8c589f851b49f4e8b59a0e2d2eec";
  };

  outputs = { self, nixpkgs }: {
    packages.x86_64-linux.duplicacy = nixpkgs.legacyPackages.x86_64-linux.duplicacy;
    packages.x86_64-linux.default = self.packages.x86_64-linux.duplicacy;
  };
}

Then I run (in the same directory)

$ /usr/bin/nix --extra-experimental-features 'nix-command flakes' build --impure .#default

And I end up with a result directory, and I can do whatever I want with the executable (add it to the PATH, or create an alias to it). Since result gets added as auto gcroot, the derivation stays around I think. This is a very nice way for anyone who does not know or care how to use nix-env or nix-shell to build packages.

The whole story of why I needed to do this is on the duplicacy discourse forum.

[Misterio77]

Some info:

For nixpkgs revs that do not have a working flake, nix shell -f <tarball> package command works as a good (but still nix-command) alternative, e.g:

nix shell -f https://github.com/nixos/nixpkgs/archive/3d6376be3583fbf45a287a3f3ed01a6aef3fa84d.tar.gz vim

While the flake.nix file itself was added in 8eaf02b9cd35def36217d39812b7c656de307c58, the oldest rev that works with newer nix versions (I'm running 2.13) is 97fc8af29b59acc55e7544a2e86b8941f9257b1e:

nix shell github:nixos/nixpkgs/97fc8af29b59acc55e7544a2e86b8941f9257b1e#vim

We could simply check if the rev is older than that and show the correct command.