add warning for running/installing on MS Windows

Author: mr-c

cwltool/main.py

@@ -12,6 +12,7 @@
 import sys
 import time
 import urllib
+import warnings
 from codecs import StreamWriter, getwriter
 from collections.abc import MutableMapping, MutableSequence
 from typing import (
@@ -1323,9 +1324,25 @@ def find_default_container(
     return default_container
 
 
-def run(*args, **kwargs):
-    # type: (*Any, **Any) -> None
+def windows_check() -> None:
+    """See if we are running on MS Windows and warn about the lack of support."""
+    if os.name == "nt":
+        warnings.warn(
+            "The CWL reference runner (cwltool) no longer supports running "
+            "CWL workflows natively on MS Windows as its previous MS Windows "
+            "support was incomplete and untested. Instead, please see "
+            "https://pypi.org/project/cwltool/#ms-windows-users "
+            "for instructions on running cwltool via "
+            "Windows Subsystem for Linux 2 (WSL2). If don't need to execute "
+            "CWL documents, then you can ignore this warning, but please "
+            "consider migrating to https://pypi.org/project/cwl-utils/ "
+            "for your CWL document processing needs."
+        )
+
+
+def run(*args: Any, **kwargs: Any) -> None:
     """Run cwltool."""
+    windows_check()
     signal.signal(signal.SIGTERM, _signal_handler)
     try:
         sys.exit(main(*args, **kwargs))

setup.py

@@ -2,10 +2,24 @@
 """Setup for the reference implementation of the CWL standards."""
 import os
 import sys
+import warnings
 
 import setuptools.command.egg_info as egg_info_cmd
 from setuptools import setup
 
+if os.name == "nt":
+    warnings.warn(
+        "The CWL reference runner (cwltool) no longer supports running "
+        "CWL workflows natively on MS Windows as its previous MS Windows "
+        "support was incomplete and untested. Instead, please see "
+        "https://pypi.org/project/cwltool/#ms-windows-users "
+        "for instructions on running cwltool via "
+        "Windows Subsystem for Linux 2 (WSL2). If don't need to execute "
+        "CWL documents, then you can ignore this warning, but please "
+        "consider migrating to https://pypi.org/project/cwl-utils/ "
+        "for your CWL document processing needs."
+    )
+
 SETUP_DIR = os.path.dirname(__file__)
 README = os.path.join(SETUP_DIR, "README.rst")
 

tests/test_windows_warning.py

@@ -0,0 +1,23 @@
+"""Test user experience running on MS Windows."""
+
+import os
+import warnings
+
+import pytest
+
+from cwltool import main
+
+# Can't be just "import cwltool ; … cwltool.main.windows_check()"
+# needs a direct import to avoid path traversal after os.name is set to "nt"
+
+
+def test_windows_warning(monkeypatch: pytest.MonkeyPatch) -> None:
+    """Confirm that the windows warning is given."""
+    with pytest.warns(UserWarning, match=r"Windows Subsystem for Linux 2"):
+        # would normally just use the MonkeyPatch object directly
+        # but if we don't use a context then os.name being "nt" causes problems
+        # for pytest on non-Windows systems. So the context unravels the change
+        # to os.name quickly, and then pytest will check for the desired warning
+        with monkeypatch.context() as m:
+            m.setattr(os, "name", "nt")
+            main.windows_check()