In reply to @pederbs:pvv.ntnu.no
nix registry may be the place to look

In reply to @pederbs:pvv.ntnu.no
nix registry may be the place to look

In reply to @pederbs:pvv.ntnu.no
make an alias?

One nice property of flakes is that I can address them as github:edolstra/hello, that's something I can remember as a human. This reference changes over time and is not reproducible. Whenever I call nix build github:edolstra/hello, Nix must inevitably somehow resolve this reference to a concrete revision. The concrete revision is a long hexadecimal string I cannot remember. Therefore I do see value in nix build to, when requested, just print the revision. Then, I can share its output (which now includes the resolved URL, which includes the hash) to my teammates, who can run the same build even if the revision that the default branch of github:edolstra/hello resolves to has changed in the meantime.

It's not a question of whether there is a possibility to somehow obtain a fully resolved flake URL, and that it can be provided as an argument to nix build, but a matter of convenience of the user experience with nix build.

One nice property of flakes is that I can address them as github:edolstra/hello, that's something I can remember as a human. This reference changes over time and is not reproducible. Whenever I call nix build github:edolstra/hello, Nix must inevitably somehow resolve this reference to a concrete revision. The concrete revision contains a long hexadecimal string I cannot remember. Therefore I do see value in nix build to, when requested, just print the revision. Then, I can share its output (which now includes the resolved URL, which includes the hash) to my teammates, who can run the same build even if the revision that the default branch of github:edolstra/hello resolves to has changed in the meantime.

It's not a question of whether there is a possibility to somehow obtain a fully resolved flake URL, and that it can be provided as an argument to nix build, but a matter of convenience of the user experience with nix build.

One nice property of flakes is that I can address them as github:edolstra/hello, that's something I can remember as a human. This reference changes over time and is not reproducible. Whenever I call nix build github:edolstra/hello, Nix must inevitably somehow resolve this reference to a concrete revision. The concrete revision contains a long hexadecimal string I cannot remember. Therefore I do see value in nix build to, when requested, just print the revision, i.e. the result of the resolution it must perform anyways. Then, I can share its output (which now includes the resolved URL, which includes the hash) to my teammates, who can run the same build even if the revision that the default branch of github:edolstra/hello resolves to has changed in the meantime.

It's not a question of whether there is a possibility to somehow obtain a fully resolved flake URL, and that it can be provided as an argument to nix build, but a matter of convenience of the user experience with nix build.

What is the flakes way of going about installing packages from different nixpkgs branches?

I have been seeing stuff like this everywhere, but no equivalent method for flakes that doesn't break reproducibility:

unstable = import <nixos-unstable> {};
environment.systemPackages = [ unstable.myPackage ];

or

unstable = fetchTarball https://github.com/NixOS/nixpkgs/archive/nixos-unstable.tar.gz

I was thinking about making an overlay using flake-utils.lib.eachDefaultSystem to instantiate nixpkgs to be set as pkgs.unstable, but this feels wrong and I'm wondering if this will cause lots of cache misses & blow up my build times.

Is there a "best practices" way of going about this?

In reply to @lehmanator:gnulinux.club

What is the flakes way of going about installing packages from different nixpkgs branches?

I have been seeing stuff like this everywhere, but no equivalent method for flakes that doesn't break reproducibility:

unstable = import <nixos-unstable> {};
environment.systemPackages = [ unstable.myPackage ];

or

unstable = fetchTarball https://github.com/NixOS/nixpkgs/archive/nixos-unstable.tar.gz

I was thinking about making an overlay using flake-utils.lib.eachDefaultSystem to instantiate nixpkgs to be set as pkgs.unstable, but this feels wrong and I'm wondering if this will cause lots of cache misses & blow up my build times.

Is there a "best practices" way of going about this?

In reply to @petrichor:envs.net
you can include it as another input to your flake, like nixpkgs-unstable.url = "github:nixos/nixpkgs/nixos-unstable";

Right, but how should I make its packages accessible by the system / home-manager?

I know I can do something like:

In reply to @petrichor:envs.net
you can include it as another input to your flake, like nixpkgs-unstable.url = "github:nixos/nixpkgs/nixos-unstable";

Right, but how should I make its packages accessible by the system / home-manager?

I know I can do something like:

In reply to @petrichor:envs.net
you can include it as another input to your flake, like nixpkgs-unstable.url = "github:nixos/nixpkgs/nixos-unstable";

Right, but how should I make its packages accessible by the system / home-manager?

I know I can do something like:

nixpkgs.overlays = [
  (final: prev: { pkgs.unstable = inputs.nixpkgs-unstable.legacyPackages.${prev.stdenv.system}; })
];

but I remember seeing one of the big maintainers saying that using a lot of overlays is discouraged and often causes slow builds, and suggested a better practice (which unfortunately I dont remember) for overriding / adding packages, but that was for one-off packages and not an entire instance of nixpkgs.

In reply to @lehmanator:gnulinux.club

What is the flakes way of going about installing packages from different nixpkgs branches?

I have been seeing stuff like this everywhere, but no equivalent method for flakes that doesn't break reproducibility:

unstable = import <nixos-unstable> {};
environment.systemPackages = [ unstable.myPackage ];

or

unstable = fetchTarball https://github.com/NixOS/nixpkgs/archive/nixos-unstable.tar.gz

I was thinking about making an overlay using flake-utils.lib.eachDefaultSystem to instantiate nixpkgs to be set as pkgs.unstable, but this feels wrong and I'm wondering if this will cause lots of cache misses & blow up my build times.

Is there a "best practices" way of going about this?

In reply to @lehmanator:gnulinux.club

What is the flakes way of going about installing packages from different nixpkgs branches?

I have been seeing stuff like this everywhere, but no equivalent method for flakes that doesn't break reproducibility:

unstable = import <nixos-unstable> {};
environment.systemPackages = [ unstable.myPackage ];

or

unstable = fetchTarball https://github.com/NixOS/nixpkgs/archive/nixos-unstable.tar.gz

I was thinking about making an overlay using flake-utils.lib.eachDefaultSystem to instantiate nixpkgs to be set as pkgs.unstable, but this feels wrong and I'm wondering if this will cause lots of cache misses & blow up my build times.

Is there a "best practices" way of going about this?

when you do outputs = { self, ... }@inputs: ...; in your flake.nix, pass inputs to specialArgs, then you can use the flake inputs and outputs (via self) in your nixos modules. maybe home manager has something like specialArgs too.

for example: https://or.computer.surgery/charles/servy-fleet/-/blob/3eae347d2cce33d1fed7371346b9d8b2aced891b/config/matrix-conduit/default.nix#L17