🐛 fix(discovery): find .exe names on Windows PATH

docs/changelog/+exe-suffixed-names.bugfix.rst

@@ -0,0 +1 @@
+On Windows, find interpreter names that already end in ``.exe``, such as ``pythonw.exe``, on ``PATH``.

src/python_discovery/_discovery.py

@@ -196,7 +196,7 @@ def path_exe_finder(
     direct = spec.str_spec
     implementation = spec.implementation.lower() if spec.implementation is not None else None
     impl_must_match = implementation in KNOWN_IMPLEMENTATIONS and implementation != "python"
-    if sys.platform == "win32":  # pragma: win32 cover
+    if sys.platform == "win32" and not direct.lower().endswith(".exe"):  # pragma: win32 cover
         direct = f"{direct}.exe"
 
     def path_exes(path: Path) -> Generator[tuple[Path, bool], None, None]:

tests/test_discovery_extra.py

@@ -14,6 +14,7 @@
     _active_versions,
     _read_python_version_file,
     _resolve_shim,
+    path_exe_finder,
     propose_interpreters,
 )
 from python_discovery._py_spec import PythonSpec
@@ -163,6 +164,25 @@ def test_path_exe_finder_returns_callable(tmp_path: Path) -> None:
     assert results == []
 
 
+@pytest.mark.parametrize(
+    ("spec", "name"),
+    [
+        pytest.param("python_custom", "python_custom.exe", id="bare-name"),
+        pytest.param("pythonw.exe", "pythonw.exe", id="exe-suffix"),
+        pytest.param("python3.13t.Exe", "python3.13t.Exe", id="mixed-case-exe-suffix"),
+    ],
+)
+def test_path_exe_finder_win32_direct_name(
+    tmp_path: Path, monkeypatch: pytest.MonkeyPatch, spec: str, name: str
+) -> None:
+    monkeypatch.setattr(sys, "platform", "win32")
+    (tmp_path / name).touch()
+
+    finder = path_exe_finder(PythonSpec.from_string_spec(spec))
+
+    assert list(finder(tmp_path)) == [(tmp_path / name, False)]
+
+
 def test_get_paths_no_path_env() -> None:
     from python_discovery._discovery import get_paths
 

tests/windows/test_windows.py

@@ -1,7 +1,10 @@
 from __future__ import annotations
 
+import os
+import shutil
 import sys
 from pathlib import Path
+from subprocess import check_call
 
 import pytest
 
@@ -60,3 +63,17 @@ def test_propose_interpreters(string_spec: str, expected_exe: str) -> None:
 
     interpreter = next(propose_interpreters(spec=PythonSpec.from_string_spec(string_spec), cache=None, env={}))
     assert interpreter.executable == expected_exe
+
+
+@pytest.mark.skipif(sys.platform != "win32", reason="Windows executable names")
+@pytest.mark.parametrize("name", ["python3.exe", "PYTHON3.EXE", "pythonw.exe"])
+def test_discovery_via_path_exe_suffixed_name(tmp_path: Path, name: str) -> None:
+    venv = tmp_path / "venv"
+    check_call([sys.executable, "-m", "venv", "--without-pip", str(venv)])
+    scripts = venv / "Scripts"
+    shutil.copyfile(scripts / "python.exe", scripts / "python3.exe")
+
+    interpreter = get_interpreter(name, [], env={"PATH": str(scripts), "SYSTEMROOT": os.environ["SYSTEMROOT"]})
+
+    assert interpreter is not None
+    assert interpreter.executable == str(scripts / name)