Work with _OLD_VIRTUAL_PATH env var like a venv activate script

Also set _OLD_VIRTUAL_PYTHONHOME like in an activate script.

This makes the virtualenv activation behaviour of the poetry and virtualenv
executors behave in a way closer to the standard.

Fix a test that previously relied on accidental PATH inheritance from the
root project venv, which is no longer possible.

poethepoet/virtualenv.py

@@ -82,15 +82,23 @@ def valid(self) -> bool:
 
     def get_env_vars(self, base_env: Mapping[str, str]) -> Dict[str, str]:
         bin_dir = str(self.bin_dir())
-        path_var = os.environ.get("PATH", "")
+        # Revert path update from existing virtualenv if applicable
+        path_var = os.environ.get("_OLD_VIRTUAL_PATH", "") or os.environ.get("PATH", "")
+        old_path_var = path_var
 
         if not path_var.startswith(bin_dir):
             path_delim = ";" if self._is_windows else ":"
             path_var = bin_dir + path_delim + path_var
 
-        result = dict(base_env, VIRTUAL_ENV=str(self.path), PATH=path_var)
+        result = dict(
+            base_env,
+            VIRTUAL_ENV=str(self.path),
+            _OLD_VIRTUAL_PATH=old_path_var,
+            PATH=path_var,
+        )
 
         if "PYTHONHOME" in result:
+            result["_OLD_VIRTUAL_PYTHONHOME"] = result["PYTHONHOME"]
             result.pop("PYTHONHOME")
 
         return result

tests/conftest.py

@@ -323,7 +323,7 @@ def use_virtualenv(
         did_exist = location.is_dir()
         assert not require_empty or not did_exist, (
             f"Test requires no directory already exists at {location}, "
-            "maybe try delete it and run again"
+            "maybe try delete it (via `poe clean`) and try again"
         )
 
         # create new virtualenv
@@ -352,7 +352,7 @@ def try_rm_dir(location: Path):
             shutil.rmtree(location)
         except:
             print(
-                "Cleanup failed. You might need to run poe clean before tests can be "
+                "Cleanup failed. You might need to run `poe clean` before tests can be "
                 "run again."
             )
 

tests/test_executors.py

@@ -21,11 +21,13 @@ def test_virtualenv_executor_fails_without_venv_dir(run_poe_subproc, projects):
 
 
 @pytest.mark.slow
-def test_virtualenv_executor_activates_venv(
+def test_virtualenv_executor_activates_venv(  # TODO: fix dependency to get poe_test_env!!
     run_poe_subproc, with_virtualenv_and_venv, projects
 ):
     venv_path = projects["venv"].joinpath("myvenv")
-    for _ in with_virtualenv_and_venv(venv_path):
+    for _ in with_virtualenv_and_venv(
+        venv_path, ["./tests/fixtures/packages/poe_test_helpers"]
+    ):
         result = run_poe_subproc("show-env", project="venv")
         assert result.capture == "Poe => poe_test_env\n"
         assert f"VIRTUAL_ENV={venv_path}" in result.stdout