[nix] add a `flake.nix` based on `flakebox`. #2212

c4lliope · 2025-10-09T18:56:17Z

See:
https://github.com/rustshop/flakebox/blob/master/docs/building-new-project.md

I opened an issue on their repo concerning a breaking API change, and had the following discussion on Matrix:

today
c4lliope joined the room

c4lliope
hello - is anyone here? I'm seeing an odd error as I go through the basic guide:
https://github.com/rustshop/flakebox/blob/master/docs/building-new-project.md#extra-dependencies

➜ hx flake.nix; nd nix build .#gitoxide
warning: Git tree '/home/calliope/disc/nvme0n1p6/code/gitoxidelabs/gitoxide' is dirty
error:
       … while evaluating the attribute 'devShells'
         at /nix/store/kwpljf3n2xlxlrq5k0p02c6kghc4n6ca-source/flake.nix:56:7:
           55|       packages.default = legacyPackages.gitoxide;
           56|       devShells = flakeboxLib.mkShells {
             |       ^
           57|         packages = [ ];

       … while evaluating the attribute 'lib.x86_64-linux'
         at /nix/store/qrv62r966lcw0pmivndiqibn24swahzy-source/flake.nix:54:7:
           53|
           54|       lib = {
             |       ^
           55|         inherit mkLib;

       error: attribute 'x86_64-linux' missing
       at /nix/store/kwpljf3n2xlxlrq5k0p02c6kghc4n6ca-source/flake.nix:34:21:
           33|       pkgs = import nixpkgs { system = arch; };
           34|       flakeboxLib = flakebox.lib.${arch} { };
             |                     ^
           35|

why would flakebox.lib.x86_64-linux be missing?

dpc ⚡️
Hello. I'm here.
Oh. I think I made backward incompat change on the master and didn't update the docs. Sorry for that!

c4lliope
oh yay.
I copied the full flake here:
rustshop/flakebox#209
oh, sure.

dpc ⚡️
rustshop/flakebox@55f2249
Now the lib contains mkLib which you use to actually create the lib with given pkgs.
If you're short on time, just trying using previous commit.

c4lliope
ah, simple enough. I'll give it a spin.

dpc ⚡️
If you want to make the world a better place you can try to update the docs where it is different. It will be some flakeboxLib = flakeboxLib.lib pkgs; kind of thing, though you might use different names.
Anyway, I'm not sure how experienced with Nix you are, there might be other adjustments needed. :D

c4lliope
seems to be building now, is a really big codebase though.

dpc ⚡️
I'm using flakebox for some really big codebases indeed.
https://github.com/fedimint/fedimint/blob/master/nix/flakebox.nix

c4lliope
ahhhh, hold up. rustc toolchain version problem?

➜ nix build .#gitoxide
warning: Git tree '/home/calliope/disc/nvme0n1p6/code/gitoxidelabs/gitoxide' is dirty
error: builder for '/nix/store/xygc7gkl4y3nncfjvls13m9vpvsgjgvh-gitoxide-deps-0.45.0.drv' failed withexit code 101;
       last 20 log lines:
       > cargoArtifacts not set, will not reuse any cargo artifacts
       > Running phase: unpackPhase
       > unpacking source archive /nix/store/plfiwc0dm7fnzy674vdiyjg66rgk1v6f-source
       > source root is source
       > Running phase: patchPhase
       > Executing configureCargoCommonVars
       > Running phase: updateAutotoolsGnuConfigScriptsPhase
       > Running phase: configurePhase
       > will append /build/source/.cargo-home/config.toml with contents of /nix/store/g64gs1ppgvzpqi5vv42ay4dl8lmgvq24-vendor-cargo-deps/config.toml
       > default configurePhase, nothing to do
       > Running phase: buildPhase
       > +++ command cargo --version
       > cargo 1.87.0 (99624be96 2025-05-06)
       > +++ command cargo check --release --locked
       > error: rustc 1.87.0 is not supported by the following package:
       >   [email protected] requires rustc 1.88
       > Either upgrade rustc or select compatible dependency versions with
       > `cargo update <name>@<current-ver> --precise <compatible-ver>`
       > where `<compatible-ver>` is the latest version supporting rustc 1.87.0
       >
       For full logs, run:
         nix log /nix/store/xygc7gkl4y3nncfjvls13m9vpvsgjgvh-gitoxide-deps-0.45.0.drv
error: 1 dependencies of derivation '/nix/store/w04flfiqxr9hbrawvzksfyj00milh3rx-gitoxide-0.45.0.drv'failed to build

yeah, gotta go unstable.

dpc ⚡️
The toolchain shipped with flakebox might be a bit out of date. I usually bring it in separately in my projects.
https://github.com/fedimint/fedimint/blob/e135fae7bdb485845dc92b5ba837f014b43e19cb/flake.nix#L17

c4lliope
If I use unstable nixpkgs, is that where it's fetching from?
sorry, my background is 90% nix 0% rust
i'll go fenix

dpc ⚡️
Fenix is good. You can get nightly and arbitrary releases, and even mix nightly rustfmt with stable toolchain etc.

c4lliope
ah, so this gitoxide codebase is a big monorepo with a bunch of sub-folders. One of those is gix-actor, and flakebox is unable to load the Cargo.toml from that pkg.

   > error: failed to load manifest for workspace member `/build/source/gix-actor`
   > referenced by workspace at `/build/source/Cargo.toml`

dpc ⚡️
Did you add it to sources?
https://github.com/rustshop/flakebox/blob/261180f894d74ab95f7afbf14c7418fedb0d3cbf/flake.nix#L78

Flakebox comes with some handy source filtering to avoid rebuilding stuff when no relevant files changed.
BTW. I hope you're aware that flakebox is mostly an opinionated wrapper around https://github.com/ipetkov/crane , mostly adding some stuff I needed and integrating cross-compilation.

c4lliope
yeah, I printed out the crane docs to my tablet so I can read through and see if there's a more minimal option.
but if this can compile before my 3pm meeting, I'm happy throwing the full arsenal at it.
oh, so the main goal is to get a .wasm out of gitoxide. I'm sure I'll need to go through and add wasm_bindgen annotations, but what would the nix build ... command look like?
is there a different system label, so nix can cross-compile? or do I handle that in the Cargo.toml target specification like the official docs say?

dpc ⚡️
https://github.com/fedimint/fedimint/blob/e135fae7bdb485845dc92b5ba837f014b43e19cb/.github/workflows/ci-nix.yml#L286
https://github.com/fedimint/fedimint/blob/e135fae7bdb485845dc92b5ba837f014b43e19cb/.github/workflows/ci-nix.yml#L213

c4lliope
holy heck.

➜ | ls result/bin/
result/bin/ein      result/bin/gix

dpc ⚡️
?

c4lliope
build is success
you all are genius. thank you so much, nixos has made getting close to rust a pain until now.
before this my flakes have only been enough for "hello world", the basics from the textbook.

See: https://github.com/rustshop/flakebox/blob/master/docs/building-new-project.md

Byron

Thanks a lot for making this happen.

I see a lot of benefit in reproducible builds and supporting more of nix in general.

However, as I am not using really using it, I think we'd need more support for maintaining it.

CI also tests the build by calling a new target in the justfile
the justfile can be used locally as well in case CI breaks for reproduction
one of the markdown files, maybe DEVELOPMENT.md should contain notes on how to get going with nix, maybe just pointing to tutorials for major unix-like platforms.

Thanks a lot.

Byron · 2025-10-12T12:34:08Z

flake.nix

@@ -0,0 +1,121 @@
+{
+  description = "`gitoxide` compiled in a nix shell, using `crane` and `flakebox`.";


Which binaries does it build specifically?

c4lliope · 2025-10-12T18:16:40Z

Closes #2211 (someday)

This builds gix and ein.
Before adding docs I'm going to look through the recommendations on http://crane.dev/ - they speak about adding wasm build targets, with sample code. They also have an example for monorepo workspaces that may be useful. At least, it's a simpler and smaller dependency than the flakebox that wraps it.

Byron · 2025-10-13T06:36:55Z

Thanks - I set it back to draft so once you undo that I will know it's ready for another review.

c4lliope · 2025-10-14T21:31:14Z

Flakebox Matrix: https://matrix.to/#/#flakebox:matrix.org

Byron · 2025-10-15T02:38:19Z

Just for clarity: I won't be joining on matrix in preference for less real-time communication here. Thanks for your understanding.

lorenzleutgeb · 2025-10-19T21:25:20Z

flake.nix

+    fenix = {
+      url = "github:nix-community/fenix";
+      inputs.nixpkgs.follows = "nixpkgs";
+    };


I do not see this input used anywhere. It is not used as an argument in line 19, and I can't find any other changes that indicate it being used. What's going on?

Suggested change

fenix = {

url = "github:nix-community/fenix";

inputs.nixpkgs.follows = "nixpkgs";

};

lorenzleutgeb · 2025-10-19T21:32:45Z

flake.nix

+        paths = [ "Cargo.toml" "Cargo.lock" ".cargo"
+
+          "etc"


Strangely formatted. Could you use a formatter, like alejandra or nixpkgs-fmt?

Suggested change

paths = [ "Cargo.toml" "Cargo.lock" ".cargo"

"etc"

paths = [

"Cargo.toml"

"Cargo.lock"

".cargo"

"etc"

lorenzleutgeb · 2025-10-19T21:32:58Z

flake.nix

+          "gix-worktree-stream"
+          "src"
+          "tests"
+


Suggested change

lorenzleutgeb · 2025-10-19T21:34:20Z

flake.nix

+
+      rustSrc = flakeboxLib.filterSubPaths {
+        root = builtins.path { name = "gitoxide"; path = ./.; };
+        paths = [ "Cargo.toml" "Cargo.lock" ".cargo"


As far as I can see, there is no .cargo file or directory in this repository. So filtering for it is confusing. Probably remove it?

Suggested change

paths = [ "Cargo.toml" "Cargo.lock" ".cargo"

paths = [ "Cargo.toml" "Cargo.lock"

lorenzleutgeb · 2025-10-19T21:37:12Z

flake.nix

+        ];
+      };
+
+      legacyPackages = (flakeboxLib.craneMultiBuild { }) (craneLib': let


Could you say why you're planning to export legacyPackages? What's the motivation here for this non-standard output?

lorenzleutgeb · 2025-10-19T21:38:07Z

flake.nix

+
+      rustSrc = flakeboxLib.filterSubPaths {
+        root = builtins.path { name = "gitoxide"; path = ./.; };
+        paths = [ "Cargo.toml" "Cargo.lock" ".cargo"


The list of paths is very long. How would this look like with a standard craneLib filter and exclusions?

[nix] add a flake.nix based on flakebox.

632d482

See: https://github.com/rustshop/flakebox/blob/master/docs/building-new-project.md

Byron requested changes Oct 12, 2025

View reviewed changes

Byron marked this pull request as draft October 13, 2025 06:36

lorenzleutgeb suggested changes Oct 19, 2025

View reviewed changes

		@@ -0,0 +1,121 @@
		{
		description = "`gitoxide` compiled in a nix shell, using `crane` and `flakebox`.";

	paths = [ "Cargo.toml" "Cargo.lock" ".cargo"
	paths = [ "Cargo.toml" "Cargo.lock"

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[nix] add a flake.nix based on flakebox. #2212

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[nix] add a flake.nix based on flakebox. #2212

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[nix] add a `flake.nix` based on `flakebox`. #2212

[nix] add a `flake.nix` based on `flakebox`. #2212