nix-flake-setup

name	nix-flake-setup
description	Activate when configuring Nix flake.nix for a Logos module. Covers flake inputs, follows declarations, preConfigure for code generation, mkLogosModule, overrides for local development, and workspace integration.

Nix Flake Setup for Logos Modules

When to Use

Use this skill when:

• Creating a flake.nix for a new Logos module
• Adding or modifying flake inputs
• Configuring the code generator in preConfigure
• Setting up local development overrides

Minimal Universal Module flake.nix

{
  description = "My Logos Module";

  inputs = {
    logos-module-builder.url = "github:logos-co/logos-module-builder";
    nix-bundle-lgx.url = "github:logos-co/nix-bundle-lgx";
  };

  outputs = inputs@{ logos-module-builder, ... }:
    logos-module-builder.lib.mkLogosModule {
      src = ./.;
      configFile = ./metadata.json;
      flakeInputs = inputs;
    };
}

No preConfigure is needed: when metadata.json declares "interface": "universal", mkLogosModule runs the universal codegen pipeline (header → .lidl → cdylib glue) automatically before CMake.

With Module Dependencies

inputs = {
  logos-module-builder.url = "github:logos-co/logos-module-builder";
  nix-bundle-lgx.url = "github:logos-co/nix-bundle-lgx";
  logos-storage-module.url = "github:logos-co/logos-storage-module";
  logos-crypto-module.url = "github:logos-co/logos-crypto-module";
};

No follows declarations needed at the individual module level — the workspace handles dependency unification via its own follows in the workspace flake.nix.

With External Libraries

inputs = {
  logos-module-builder.url = "github:logos-co/logos-module-builder";
  nix-bundle-lgx.url = "github:logos-co/nix-bundle-lgx";
  my-ext-lib = {
    url = "github:org/my-lib/<commit-hash>";
    flake = false;
  };
};

outputs = inputs@{ logos-module-builder, ... }:
  logos-module-builder.lib.mkLogosModule {
    src = ./.;
    configFile = ./metadata.json;
    flakeInputs = inputs;
    externalLibInputs = {
      mylib = inputs.my-ext-lib;
    };
  };

The externalLibInputs key must match the name in metadata.json nix.external_libraries.

mkLogosModule Parameters

Parameter	Required	Description
src	Yes	Source directory (usually ./.)
configFile	Yes	Path to metadata.json
flakeInputs	Yes	Pass inputs to make all flake inputs available
externalLibInputs	No	Map of external library names to flake inputs
preConfigure	No	Shell script to run before CMake (code generator)

Local Development with Overrides

Test with local changes to a dependency:

# Manual override
nix build --override-input logos-storage-module path:../logos-storage-module

# Via workspace CLI (auto-detects dirty repos)
ws build my-module --auto-local

# Explicit local overrides
ws build my-module --local logos-storage-module logos-cpp-sdk

Key Rules

• All flake inputs must be tracked by git (git add flake.nix flake.lock)
• nixpkgs is inherited through logos-module-builder (never pin separately)
• Qt version comes from logos-cpp-sdk (never override)
• preConfigure runs BEFORE cmake — this is where the code generator goes
• The nix-bundle-lgx input enables LGX packaging outputs