In general it is very nice. A common method is you create a `default.nix` file in the project you are working on and use tools that manage the deps for you. For example:

Rust+Cargo: https://gitlab.com/kevincox/watchlog/-/blob/22c877065f763b3d...

Node+NPM: https://gitlab.com/kevincox/kevincox-web-compiler/-/blob/9fa...

My only Ruby project is private but I just rolled my own with:

    export "GEM_HOME=$out"
    bundle install --jobs $NIX_BUILD_CORES

Then I can set the resulting derivation as $GEM_HOME in the build step.

And sorry, but I don't do much Python.

For development you then use nix-shell to build the environment with all of the dependencies available. The downside is that you either need to commit the default.nix to the project, or configure it to be ignored. But the advantage is that it handles everything for you. For example you can configure native libraries such as PostgreSQL client or openssl without worrying if they are installed on your system. This means that the entire dev environment is tested in CI (assuming that you run nix-build in CI).

This is also nicer than docker/VM based dev environments as it just prefixes your usual environment with the deps, so you still have your regular commands and development tools available.