nix-filter - a small self-container source filtering lib

STATUS: unstable

A cool way to include only what you need.

When using nix within a project, developers often use src = ./.; for a project like this:

{ stdenv }:
stdenv.mkDerivation {
  name = "my-project";
  src = ./.;
}

This works but has an issue; on each build, nix will copy the whole project source code into the /nix/store. Including the .git folder and any temporary files left over by the editor.

The main workaround is to use either builtins.fetchGit ./. or one of the many gitignore filter projects but this is not precise enough. If the project README changes, it should rebuild the project. If the nix code changes, it shouldn't rebuild the project. That's why this project exists. I want total control.

Example usage

{ stdenv, nix-filter }:
stdenv.mkDerivation {
  name = "my-project";
  src = nix-filter {
    path = ./.;
    allow = [
      "src" # strings are automatically converted to ./src filter
      ./package.json # paths are automatically converted to path filters
      (nix-filter.byExt "js") # create your own filters like that
    ];

    # TODO: doesn't work yet
    deny = [
    ];
  };
}