🐛 fix(discovery): match relative interpreter paths with ".."

docs/changelog/158.bugfix.rst

@@ -0,0 +1,2 @@
+Accept relative interpreter paths that step up a directory, such as ``../venv/bin/python``, which were found and
+queried but never matched the spec.

src/python_discovery/_discovery.py

@@ -158,7 +158,8 @@ def _check_exe(path: str, tested_exes: set[str]) -> str | None:
     if exe_id in tested_exes:
         return None
     tested_exes.add(exe_id)
-    return str(Path(path).absolute())
+    # unlike Path.absolute(), abspath collapses "..", which PythonInfo._satisfies_path relies on
+    return os.path.abspath(path)
 
 
 def _is_new_exe(exe_raw: str, tested_exes: set[str]) -> bool:

tests/test_discovery.py

@@ -93,6 +93,25 @@ def test_relative_path(session_cache: DiskCache, monkeypatch: pytest.MonkeyPatch
     assert result is not None
 
 
+@pytest.mark.parametrize(
+    "sep",
+    [
+        pytest.param("/", id="slash"),
+        pytest.param("\\", id="backslash", marks=pytest.mark.skipif(not IS_WIN, reason="Windows separator")),
+    ],
+)
+def test_relative_path_with_parent_reference(
+    session_cache: DiskCache, monkeypatch: pytest.MonkeyPatch, sep: str
+) -> None:
+    sys_executable = Path(PythonInfo.current_system(session_cache).system_executable)
+    monkeypatch.chdir(str(sys_executable.parent))
+    relative = sep.join((os.pardir, sys_executable.parent.name, sys_executable.name))
+    result = get_interpreter(relative, [], session_cache)
+    assert result is not None
+    assert os.pardir not in Path(result.executable).parts
+    assert Path(result.executable).samefile(sys_executable)
+
+
 def test_discovery_fallback_fail(session_cache: DiskCache, caplog: pytest.LogCaptureFixture) -> None:
     caplog.set_level(logging.DEBUG)
     result = get_interpreter(["magic-one", "magic-two"], cache=session_cache)

tests/test_iter_interpreters.py

@@ -64,6 +64,20 @@ def test_iter_interpreters_with_abs_path_yields_one(session_cache: DiskCache) ->
     assert results[0].executable == sys.executable
 
 
+@pytest.mark.usefixtures("uv_dir")
+def test_iter_interpreters_relative_path_with_parent_reference(
+    session_cache: DiskCache, monkeypatch: pytest.MonkeyPatch
+) -> None:
+    sys_executable = Path(PythonInfo.current_system(session_cache).system_executable)
+    monkeypatch.chdir(str(sys_executable.parent))
+    monkeypatch.setenv("PATH", "")
+    relative = str(Path(os.pardir) / sys_executable.parent.name / sys_executable.name)
+    results = list(iter_interpreters(relative, cache=session_cache))
+    assert len(results) == 1
+    assert os.pardir not in Path(results[0].executable).parts
+    assert Path(results[0].executable).samefile(sys_executable)
+
+
 def test_iter_interpreters_sequence_dedups_across_keys(session_cache: DiskCache) -> None:
     results = list(iter_interpreters([sys.executable, sys.executable], cache=session_cache))
     assert len(results) == 1