flake-parts

The flake-parts integration requires conan-flake and infuse to be added to the flake inputs:

# file: examples/flake-parts/flake.nix
{
  inputs = {
    nixpkgs.url = "github:cachix/devenv-nixpkgs/rolling";
    flake-parts.url = "github:hercules-ci/flake-parts";
    treefmt-nix.url = "github:numtide/treefmt-nix";

    # Add these two:
    conan-flake.url = "git+https://codeberg.org/tarcisio/conan-flake";
    infuse = {
      url = "git+https://codeberg.org/amjoseph/infuse.nix?rev=364ea18b5611b5fd6a6acd7151411b430a70e194";
      flake = false;
    };
  };
  # ...
}

After importing inputs.conan-flake.flakeModule, it’s possible to use the options from perSystem.conan to configure a suitable Conan profile:

# file: examples/flake-parts/flake.nix
{
  # ...
  outputs = inputs@{ self, nixpkgs, flake-parts, ... }:
    flake-parts.lib.mkFlake { inherit inputs; } {
      systems = nixpkgs.lib.systems.flakeExposed;

      imports = [
        inputs.conan-flake.flakeModule # Import this module
        inputs.treefmt-nix.flakeModule
      ];

      perSystem = { pkgs, config, ... }: {

        # A suitable Conan profile:
        conan = {
          profiles.default = {
            settings.build_type = "Release";
            settings."compiler.cppstd" = "23";
          };
        };

        devShells.default = pkgs.mkShell {
          inputsFrom = [
            # conan-flake computes a devShell that can be used directly or
            # appended to the `inputsFrom` option of another devShell as a
            # means to compose with other devShell modules:
            config.conan.outputs.devShell
            config.treefmt.build.devShell
          ];
          packages = [ pkgs.just ];
        }; # devShells

        treefmt.config = {
          projectRoot = self;
          projectRootFile = "README.md";
          programs = {
            cmake-format.enable = true;
          };
        };
      };
    };
}

The example above can be found in the examples/flake-parts directory:

cd examples/flake-parts
direnv allow .

It can take a while before completing. After that, the conan command should be available in the path, and the required profile and other Conan settings already in place:

conan profile show

A Release, C++23 profile is expected:

Host profile:
[settings]
arch=x86_64
build_type=Release
compiler=gcc
compiler.cppstd=23
compiler.libcxx=libstdc++11
compiler.version=15.3.0
os=Linux
[platform_tool_requires]
cmake/4.3.4
[conf]


Build profile:
[settings]
arch=x86_64
build_type=Release
compiler=gcc
compiler.cppstd=23
compiler.libcxx=libstdc++11
compiler.version=15.3.0
os=Linux
[platform_tool_requires]
cmake/4.3.4
[conf]

Note

By default, conan-flake sets both CMake and the configured stdenv.cc compiler as devShell.tools. Also, whatever CMake version, if any, ends up being in the devShell.tools is also set, by default, as a profiles.<name>.platformToolRequires of every profile.

The resulting default devShell defined above is a composition — it merges config.conan.outputs.devShell and config.treefmt.build.devShell, and appends pkgs.just to the resulting devShell’s package list for its own sake:

devShells.default = pkgs.mkShell {
  inputsFrom = [
    # conan-flake computes a devShell that can be used directly or
    # appended to the `inputsFrom` option of another devShell as a
    # means to compose with other devShell modules:
    config.conan.outputs.devShell
    config.treefmt.build.devShell
  ];
  packages = [ pkgs.just ];
}; # devShells

A possible sanity check could be to find the corresponding commands available in the path:

cmake --version
conan --version
treefmt --version
echo
just --version

Also, CMake’s version should match the one listed in the [platform_tool_requires] section of the conan profile show command’s output above:

cmake version 4.3.4

CMake suite maintained and supported by Kitware (kitware.com/cmake).
Conan version 2.32.0-dev
treefmt v2.5.0
just 1.57.0

The complete list of the options available under perSystem.conan, along with the initial setup instructions for flake-parts scenarios, is in the option reference.