Add conda-direnv package

packages/conda-direnv/default.nix

@@ -0,0 +1,50 @@
+{
+  # Snowfall Lib provides a customized `lib` instance with access to your flake's library
+  # as well as the libraries available from your flake's inputs.
+  lib,
+  # You also have access to your flake's inputs.
+  inputs,
+
+  # All other arguments come from NixPkgs. You can use `pkgs` to pull packages or helpers
+  # programmatically or you may add the named attributes as arguments here.
+  pkgs,
+  stdenv,
+  ...
+}:
+
+pkgs.writeShellApplication {
+  name = "conda-direnv";
+
+  runtimeInputs = with pkgs; [
+    conda
+    yq
+  ];
+
+  text = ''
+    if [ ! -f environment.yml ]; then
+       echo "environment.yml does not exist! Exiting..."
+       exit 1
+    fi
+
+    ENV_NAME=$(${pkgs.yq}/bin/yq ".name" environment.yml -r)
+    if [ "$ENV_NAME" == "" ] || [ "$ENV_NAME" == "null" ]; then
+        echo "Property \"name\" not in environment.yml or empty! Exiting..."
+        exit 1
+    fi
+
+    echo Welcome to your conda environment "$ENV_NAME"! Activating...
+
+    condanew() {
+        conda env create -f environment.yml -n $ENV_NAME
+        conda activate $ENV_NAME
+    }
+
+    exec ${pkgs.conda}/bin/conda-shell
+    conda activate $ENV_NAME || condanew
+
+    echo "Environment active! To update it, run:"
+    echo -e "\tconda env update -f environment.yml -n $ENV_NAME"
+
+    "$SHELL" # needs to be last line so that conda-shell actually enters a shell
+  '';
+}