fix: recreate if broken symlinks are present (#1078)

henryiii · web-flow · commit e0f64e6c3cb2 · 2026-04-09T16:30:34.000-04:00
* fix: recreate if broken symlinks are present

Signed-off-by: Henry Schreiner &lt;henryfs@princeton.edu&gt;

* tests: ignore encoding warning from conda

Signed-off-by: Henry Schreiner &lt;henryfs@princeton.edu&gt;

* tests: avoid warning when calling conda instead

Signed-off-by: Henry Schreiner &lt;henryfs@princeton.edu&gt;

* tests: try different mechanism

Signed-off-by: Henry Schreiner &lt;henryfs@princeton.edu&gt;

* Remove reset_python_warn_env fixture

Removed the reset_python_warn_env fixture to avoid issues with conda tests on Windows.

---------

Signed-off-by: Henry Schreiner &lt;henryfs@princeton.edu&gt;
diff --git a/nox/virtualenv.py b/nox/virtualenv.py
@@ -603,6 +603,7 @@ def _clean_location(self) -> bool:
             if (
                 self.reuse_existing
                 and self._check_reused_environment_type()
+                and self._check_reused_environment_links()
                 and self._check_reused_environment_interpreter()
             ):
                 return False
@@ -611,6 +612,23 @@ def _clean_location(self) -> bool:
                 shutil.rmtree(self.location, ignore_errors=True)
         return True
 
+    def _check_reused_environment_links(self) -> bool:
+        """Check that interpreter links in the reused environment are not broken."""
+        bin_dir = self.bin
+        names = (
+            ["python.exe"]
+            if _PLATFORM.startswith("win") and not _IS_MINGW
+            else ["python", "python3"]
+        )
+
+        for name in names:
+            path = os.path.join(bin_dir, name)
+            # ``lexists`` catches broken symlinks, ``exists`` verifies the target.
+            if os.path.lexists(path) and not os.path.exists(path):
+                return False
+
+        return True
+
     def _read_pyvenv_cfg(self) -> dict[str, str] | None:
         """Read a pyvenv.cfg file into dict, returns None if missing."""
         path = os.path.join(self.location, "pyvenv.cfg")
diff --git a/tests/test_virtualenv.py b/tests/test_virtualenv.py
@@ -539,6 +539,35 @@ def test_create_reuse_environment_with_different_interpreter(
     assert not location.joinpath("marker").exists()
 
 
+@pytest.mark.skipif(IS_WINDOWS, reason="Uses POSIX symlinks.")
+@pytest.mark.parametrize(
+    "venv_backend",
+    [
+        "venv",
+        "virtualenv",
+        pytest.param("uv", marks=has_uv),
+    ],
+)
+def test_create_reuse_environment_with_broken_interpreter_symlink(
+    make_one: Callable[..., tuple[VirtualEnv | ProcessEnv, Path]],
+    venv_backend: str,
+) -> None:
+    venv, location = make_one(reuse_existing=True, venv_backend=venv_backend)
+    venv.create()
+
+    marker = location.joinpath("marker")
+    marker.touch()
+
+    python = location.joinpath("bin", "python")
+    python.unlink()
+    python.symlink_to("/definitely/missing/python")
+
+    reused = not venv.create()
+
+    assert not reused
+    assert not marker.exists()
+
+
 @has_uv
 def test_create_reuse_stale_venv_environment(
     make_one: Callable[..., tuple[VirtualEnv | ProcessEnv, Path]],
