[nyarlathotep_]

My Nix experience is limited, so forgive my ignorance here, but is it possible to create a development environment for an "older" project as well?

Say I need some 3.20 version of CMake and gcc 9/whatever or something--i assume such a thing is possible, but I've not seen a simple way to "pin versions" of things the way you would in say a language's package manager.

[klodolph]

My Nix experience is pretty limited, too. Nix is not great at pinning to specific versions.

If your older project was made in Nix, it’s no problem. You just check out the old copy of the project and you automatically get the old copy of the dependencies.

If your old project needs some specific major version of GCC, going back to like 4.8, there are specific packages in Nix. You just add “gcc48” to your dependencies and you get GCC 4.8. You still get newer versions of e.g. binutils.

If your old project needs a specific version of CMake, I know two ways to get that, but they’re a little ugly.

First method is to import an old <nixpkgs> containing the right version of CMake, and then import that into your environment. You search through Git history of the nixpkgs repository until you find one with the correct version. Yes, this sounds awful. It’s not that bad. I’m not sure how to do this with flakes.

You can also copy the CMake derivation into your project and modify it to compile & build the version of CMake you like. This is the approach I would normally use, most of the time.

There may be easier ways to do this. I’m not sure.

[nyarlathotep_]

Thanks, that clears up my understanding. I'd suspected it was something along those lines.

[lexlash]

https://www.nixhub.io/ - and I’ve seen others - make the searching easy. It’s odd to me that I rely so much on web based tools (like search.nixos.org!) to look up nixpkgs details for my commandline but eh.

For a flake, you’d specify an input of that specific revision of nixpkgs and then refer to your CMake dependency with respect to that input. You may end up with - by design - a lot of duplicated dependencies, but it’d work.

https://blog.mplanchard.com/posts/installing-a-specific-vers... is a nice writeup (not mine) with examples of a few different ways to do this in flakes and not-flakes.

[klodolph]

Yeah, relying on `search.nixos.org` is a little weird. Package discovery overall is a little weird… I think I usually do it through nix repl.