[microtonal]

as that turns a simple 'nix build' into

Which reveals another annoying thing about using flakes for development. It copies every time you build something the whole darn project into the Nix store. Fine when you have a small project, but with large projects this becomes a significant overhead.

[ParetoOptimal]

> It copies every time you build something the whole darn project into the Nix store. Fine when you have a small project, but with large projects this becomes a significant overhead.

Isn't copying the repo to a read only location just inherent to the problem of reproducibility?

[grumbel]

Not necessarily, most build systems allow you to separate source input and build output. So grabbing the source from the current directly is a possibility, if the build script is clean and doesn't do anything weird in the source directory.

In Nix you can get that via 'nix develop', which gives you a shell with access to the individual build phases and with a bit of tweaking, allows you to run them from your source directory without copying the source around first (see 'declare -f genericBuild').

[grumbel]

When you build into the store, you have to rebuild from scratch. However Nix does allow incremental builds inside your source directory as well. If you spawn a development shell like:

    nix develop .

All the build phases are available as shell functions or variables (unpackPhase, patchPhase, configurePhase, buildPhase, ...). The phases depend on each other, so if you want to skip a phase some additional tweaking or setting of environment variables will be necessary. The "genericBuild" function is the top level entry point for a normal build, the source can be viewed via:

   declare -f genericBuild

and should give a bit of an idea what Nix is doing.