🔧 Add flake.nix for creating dev shells with nix. (#1253)

This enables user with nix installed to work on pyglotaran. The flake creates a shell with python 3.10 and virtualenv installed and installs all dependencies on first creation.

.gitignore

@@ -13,6 +13,8 @@ pyvenv.cfg
 /.venv*
 /venv*
 /.env/
+/.direnv/
+.envrc
 
 # sensitive environment variables
 .env

flake.nix

@@ -0,0 +1,52 @@
+{
+  inputs = {
+    nixpkgs = {
+      url = "github:nixos/nixpkgs/nixos-unstable";
+    };
+    flake-utils = {
+      url = "github:numtide/flake-utils";
+    };
+  };
+  outputs = { nixpkgs, flake-utils, ... }: flake-utils.lib.eachDefaultSystem (system:
+    let
+      pkgs = import nixpkgs {
+        inherit system;
+      };
+      python = pkgs.python310;
+      lib-path = with pkgs; lib.makeLibraryPath [
+        stdenv.cc.cc
+      ];
+
+
+    in
+    rec {
+      devShell = pkgs.mkShell {
+        buildInputs = with pkgs; [
+          python
+          pre-commit
+          (python3.withPackages (ps: with ps; [
+            virtualenvwrapper
+          ]))
+        ];
+        shellHook = ''
+          # Augment the dynamic linker path
+          export "LD_LIBRARY_PATH=$LD_LIBRARY_PATH:${lib-path}"
+
+          # Setup the virtual environment if it doesn't already exist.
+          VENV=.venv
+          if test ! -d $VENV; then
+            virtualenv $VENV
+            # Install Python dependencies
+            pip install -r requirements_dev.txt
+            pip install -e .
+          fi
+          source ./$VENV/bin/activate
+          export PYTHONPATH=`pwd`/$VENV/${python.sitePackages}/:$PYTHONPATH
+
+          pre-commit install
+        '';
+
+      };
+    }
+  );
+}

pyproject.toml

@@ -77,6 +77,8 @@ ignore = [
   ".sourcery.yaml",
   ".zenodo.json",
   "codecov.yml",
+  "flake.nix",
+  "flake.lock",
   "readthedocs.yml",
   "requirements_dev.txt",
   "tox.ini",