* Introduction

~venv-manager~ is a set of nix modules that defines basic configurations for
~nix-shell~, aiming to make it easier to declaratively manage virtual
environments for different development frameworks.

[[https://nixos.org/][NixOS]] indeed has, among others, two great advantages :
- the ability to declaratively create virtual environments in =shell.nix= files
  that may then be activated with =nix-shell= ;
- the ability to enable many services in a single statement thanks to a huge
  database of crowdsourced service configurations.

But creating a new virtual environment may end up being non trivial and
cumbersome, because =nix-shell= doesn't have a similar database of crowdsourced
configurations. Consider the example of OCaml virtual environments. Simply using
the =shell.nix= file given by
#+BEGIN_SRC nix
  { pkgs ? import <nixpkgs> {} }:
  { 
    buildInputs = with pkgs; [ ocaml ocamlPackages.lwt ]; 
  } 
#+END_SRC
will not be enough as the =ocaml= binary needs to be made aware of the existence
of the =lwt= library. After looking up how to do so, the user may then add the
corresponding configuration to =shell.nix= (see [[file:modules/ocaml.nix]] for the
solution). But creating another similar environment will require to either
rewrite the same code or to find the previous file and copy it.

=venv-manager= aims to fill that gap by using the modularity of Nix to provide
common configurations for virtual environments that may be enabled in a whim.
Now creating the same OCaml environment only requires the following declaration.
#+BEGIN_SRC nix
  {
    ocaml = {
      enable = true;
      packages = ocamlPackages: [ ocamlPackages.lwt ];
    };
  }
#+END_SRC

* Setup

To use =venv-manager=, clone this repository in =~/.config/venv-manager=. A new
virtual environment configuration can then be created by copying the
=shell-template.nix= (use an alias for that !) and filling in the =settings=
attribute set.