Add a Nix Flake

[Toby222]

Description of Changes

Create a Nix flake so that SpacetimeDB is to some degree usable via nix :^)
Also formatted the single not-properly-formatted source file in the codebase out of habit (I can remove this if desired)

As-is the binaries it creates are the package names, not sure if that's desired or not.

API and ABI breaking changes

If this is an API or ABI breaking change, please apply the
corresponding GitHub label.

Expected complexity level and risk

How complicated do you think these changes are? Grade on a scale from 1 to 5,
where 1 is a trivial change, and 5 is a deep-reaching and complex change.
2

This complexity rating applies not only to the complexity apparent in the diff,
but also to its interactions with existing and future code.
I did my best to make it as low-maintenance as possible. Unless new binaries get added, or their dependencies change this should keep working indefinitely. And in case that happens I tried to make the changes required as minimal as possible (cf. lines ~105 in flake.nix)

If you answered more than a 2, explain what is complex about the PR,
and what other components it interacts with in potentially concerning ways.
n/A

Testing

Describe any testing you've done, and any testing you'd like your reviewers to do,
so that you're confident that all the changes work as expected!

• Built and ran the programs in NixOS
• Make sure the overlay works

[axman6]

I've got nothing to do with the project, but came here looking for a flake.nix or default.nix, so thought I'd review. Looks good to me, just some minor cleanups.

[PrestonHager]

I've also used the nix flake, and it worked great! I was able to install it into some local flakes using the following dev shell:

{
  inputs = {
    nixpkgs.url = "github:NixOS/nixpkgs/nixpkgs-unstable";
    flake-utils.url = "github:numtide/flake-utils";

    # Spacetime DB flake
    spacetime = {
      url = "github:Toby222/SpacetimeDB";
      #inputs.nixpkgs.follows = "nixpkgs";
    };
  };

  # create a dev shell for each system using flake-utils
  outputs = { self, nixpkgs, flake-utils, spacetime }:
    flake-utils.lib.eachDefaultSystem (system:
    let pkgs = nixpkgs.legacyPackages.${system}; in {
      devShells = {
        default = pkgs.mkShell {
          packages = with pkgs; [
            rustc
            cargo
            llvmPackages.bintools
            # web assembly packages
            binaryen
          ] ++ [
            spacetime.packages.${system}.spacetimedb-cli
          ];
        };
      };
    }
  );
}

I don't love that the binary provided through the flake is spacetimedb-cli instead of the upstream's spacetime binary. A simple alias will fix this, but is it possible to change the flake to provide spacetime as the name instead?

Also, one small suggestion on using "${var}" should be $var instead. I can't find any references in nix documentation, it was a suggestion from the nixpkgs team when I made a pull request awhile ago. It seems like there is not a standard in using variables by themselves in nix strings.

[Toby222]

I don't love that the binary provided through the flake is spacetimedb-cli instead of the upstream's spacetime binary. A simple alias will fix this, but is it possible to change the flake to provide spacetime as the name instead?

Same, definitely fixable, probably best to make an extra derivation that wraps -cli and -standalone? Not quite sure how

Also, one small suggestion on using "${var}" should be $var instead. I can't find any references in nix documentation, it was a suggestion from the nixpkgs team when I made a pull request awhile ago. It seems like there is not a standard in using variables by themselves in nix strings.

Doesn't work with property paths afaict.