packaging-nix: Add villas-python package

Signed-off-by: Philipp Jungkamp <Philipp.Jungkamp@opal-rt.com>

packaging/nix/flake.nix

@@ -97,6 +97,10 @@
     packagesWith = pkgs: rec {
       default = villas;
 
+      villas-python = pkgs.callPackage ./python.nix {
+        src = ../../python;
+      };
+
       villas-minimal = pkgs.callPackage ./villas.nix {
         src = ../..;
         version = "minimal";

packaging/nix/python.nix

@@ -0,0 +1,23 @@
+# SPDX-FileCopyrightText: 2023 OPAL-RT Germany GmbH
+# SPDX-License-Identifier: Apache-2.0
+{
+  src,
+  python3Packages,
+  villas-minimal,
+}:
+python3Packages.buildPythonPackage {
+  name = "villas-python";
+  src = src;
+  propagatedBuildInputs = with python3Packages; [
+    linuxfd
+    requests
+    villas-minimal
+  ];
+  nativeCheckInputs = with python3Packages; [
+    black
+    flake8
+    mypy
+    pytest
+    types-requests
+  ];
+}

python/.envrc

@@ -0,0 +1,36 @@
+# SPDX-FileCopyrightText: 2014-2023 Institute for Automation of Complex Power Systems, RWTH Aachen University
+# SPDX-License-Identifier: Apache-2.0
+
+export_or_unset()
+{
+	local var=$1
+
+	if [ -z "${!var+x}" ]; then
+		return
+	fi
+
+	if [ -n "$2" ]; then
+		export $var="$2"
+	else
+		unset $var
+	fi
+
+}
+
+if direnv_version "2.30.0" \
+&& has nix \
+&& nix show-config experimental-features 2>/dev/null | grep -wqF flakes
+then
+	local oldtmp="$TMP"
+	local oldtemp="$TEMP"
+	local oldtmpdir="$TMPDIR"
+	local oldtempdir="$TEMPDIR"
+
+	watch_file ../packaging/nix/*.nix
+	use flake ../packaging/nix#villas-python
+
+	export_or_unset TMP "$oldtmp"
+	export_or_unset TEMP "$oldtemp"
+	export_or_unset TMPDIR "$oldtmpdir"
+	export_or_unset TEMPDIR "$oldtempdir"
+fi