python: Enter directory when creating venv

This commit does several things in one go:

1. Fixes `libstdc++.so.6` issues due to poetry using unwrapped Python
   when used in combination with `languages.python.directory`. This was
   because the `poetry env use` wasn't given the source directory.

2. Fixes poetry creating incorrect shebangs because
   `languages.python.directory` is a relative path. This is a known
   issue: python-poetry/poetry#9415

3. Cleans up the bash code by using pushd/popd.

src/modules/languages/python.nix

@@ -40,11 +40,13 @@ let
   };
 
   initVenvScript = pkgs.writeShellScript "init-venv.sh" ''
+    pushd "${cfg.directory}"
+
     # Make sure any tools are not attempting to use the Python interpreter from any
     # existing virtual environment. For instance if devenv was started within an venv.
     unset VIRTUAL_ENV
 
-    VENV_PATH="${config.env.DEVENV_STATE}/${lib.optionalString (cfg.directory != config.devenv.root) ''"${cfg.directory}/"''}venv"
+    VENV_PATH="venv"
 
     profile_python="$(${readlink} ${package.interpreter})"
     devenv_interpreter_path="$(${pkgs.coreutils}/bin/cat "$VENV_PATH/.devenv_interpreter" 2> /dev/null || echo false )"
@@ -92,9 +94,13 @@ let
             }
        fi
     fi
+
+    popd
   '';
 
   initPoetryScript = pkgs.writeShellScript "init-poetry.sh" ''
+    pushd "${cfg.directory}"
+
     function _devenv_init_poetry_venv
     {
       # Make sure any tools are not attempting to use the Python interpreter from any
@@ -107,12 +113,12 @@ let
 
     function _devenv_poetry_install
     {
-      local POETRY_INSTALL_COMMAND=(${cfg.poetry.package}/bin/poetry install --no-interaction ${lib.concatStringsSep " " cfg.poetry.install.arguments} ${lib.optionalString (cfg.directory != config.devenv.root) ''--directory=${cfg.directory}''})
+      local POETRY_INSTALL_COMMAND=(${cfg.poetry.package}/bin/poetry install --no-interaction ${lib.concatStringsSep " " cfg.poetry.install.arguments})
       # Avoid running "poetry install" for every shell.
       # Only run it when the "poetry.lock" file or Python interpreter has changed.
       # We do this by storing the interpreter path and a hash of "poetry.lock" in venv.
-      local ACTUAL_POETRY_CHECKSUM="${package.interpreter}:$(${pkgs.nix}/bin/nix-hash --type sha256 "$DEVENV_ROOT"/${lib.optionalString (cfg.directory != config.devenv.root) ''${cfg.directory}/''}pyproject.toml):$(${pkgs.nix}/bin/nix-hash --type sha256 "$DEVENV_ROOT"/${lib.optionalString (cfg.directory != config.devenv.root) ''${cfg.directory}/''}poetry.lock):''${POETRY_INSTALL_COMMAND[@]}"
-      local POETRY_CHECKSUM_FILE="$DEVENV_ROOT"/${lib.optionalString (cfg.directory != config.devenv.root) ''${cfg.directory}/''}.venv/poetry.lock.checksum
+      local ACTUAL_POETRY_CHECKSUM="${package.interpreter}:$(${pkgs.nix}/bin/nix-hash --type sha256 pyproject.toml):$(${pkgs.nix}/bin/nix-hash --type sha256 poetry.lock):''${POETRY_INSTALL_COMMAND[@]}"
+      local POETRY_CHECKSUM_FILE=".venv/poetry.lock.checksum"
       if [ -f "$POETRY_CHECKSUM_FILE" ]
       then
         read -r EXPECTED_POETRY_CHECKSUM < "$POETRY_CHECKSUM_FILE"
@@ -131,7 +137,7 @@ let
       fi
     }
 
-    if [ ! -f "$DEVENV_ROOT"/${lib.optionalString (cfg.directory != config.devenv.root) ''${cfg.directory}/''}pyproject.toml ]
+    if [ ! -f "pyproject.toml" ]
     then
       echo "No pyproject.toml found. Run 'poetry init' to create one." >&2
     else
@@ -140,9 +146,11 @@ let
         _devenv_poetry_install
       ''}
       ${lib.optionalString cfg.poetry.activate.enable ''
-        source "$DEVENV_ROOT"/${lib.optionalString (cfg.directory != config.devenv.root) ''${cfg.directory}/''}.venv/bin/activate
+        source .venv/bin/activate
       ''}
     fi
+
+    popd
   '';
 in
 {

tests/python-native-libs-poetry/.test.sh

@@ -0,0 +1,5 @@
+python -c "from PIL import Image"
+python -c "import grpc_tools.protoc"
+python -c "import transformers"
+
+# TODO: invoke a subprocess with an old glibc and assert it doesn't crash

tests/python-native-libs-poetry/devenv.nix

@@ -0,0 +1,9 @@
+{ pkgs, lib, ... }: {
+  packages = [ pkgs.cairo ];
+
+  languages.python = {
+    enable = true;
+    directory = "subdir";
+    poetry.enable = true;
+  };
+}