A simple demonstration of writing a top-level flake.nix that delegates to the inner default.nix (flake alike) of a sub-project. This pattern is useful in monorepos with many sub-projects written in different programming languages.

Files of interest:

• flake.nix -- top-level flake
• haskell/project.nix -- haskell flake-alike
• rust/project.nix -- rust flake-alike

Features

• Haskell app statically links to Rust library
• Works on Linux and macOS (M1)
• IDE experience works for both languages through HLS.
• Autoformat by treefmt

The Haskell programs links with the Rust library.

nix develop -c sh -c "cd ./haskell && cabal run"

nix develop -c sh -c "cd ./rusty && cargo build"

Run the full program,

nix run

Just build it,

nix build

• https://github.com/hercules-ci/flake-parts