gh-90473: Misc test fixes for WASI (GH-93218)

* ``sys.executable`` is not set
* WASI does not support subprocess
* ``pwd`` module is not available
* WASI checks ``open`` syscall flags more strict, needs r, w, rw flag.
* ``umask`` is not available
* ``/dev/null`` may not be accessible

Lib/distutils/tests/test_build.py

@@ -12,6 +12,7 @@ class BuildTestCase(support.TempdirManager,
                     support.LoggingSilencer,
                     unittest.TestCase):
 
+    @unittest.skipUnless(sys.executable, "test requires sys.executable")
     def test_finalize_options(self):
         pkg_dir, dist = self.create_dist()
         cmd = build(dist)

Lib/lib2to3/tests/test_parser.py

@@ -63,7 +63,7 @@ def test_load_grammar_from_pickle(self):
 
     @unittest.skipIf(sys.executable is None, 'sys.executable required')
     @unittest.skipIf(
-        sys.platform == 'emscripten', 'requires working subprocess'
+        sys.platform in {'emscripten', 'wasi'}, 'requires working subprocess'
     )
     def test_load_grammar_from_subprocess(self):
         tmpdir = tempfile.mkdtemp()

Lib/test/test_netrc.py

@@ -1,6 +1,11 @@
 import netrc, os, unittest, sys, textwrap
 from test.support import os_helper, run_unittest
 
+try:
+    import pwd
+except ImportError:
+    pwd = None
+
 temp_filename = os_helper.TESTFN
 
 class NetrcTestCase(unittest.TestCase):
@@ -266,6 +271,7 @@ def test_comment_at_end_of_machine_line_pass_has_hash(self):
 
 
     @unittest.skipUnless(os.name == 'posix', 'POSIX only test')
+    @unittest.skipIf(pwd is None, 'security check requires pwd module')
     def test_security(self):
         # This test is incomplete since we are normally not run as root and
         # therefore can't test the file ownership being wrong.

Lib/test/test_os.py

@@ -1765,6 +1765,7 @@ def test_remove_nothing(self):
         self.assertTrue(os.path.exists(os_helper.TESTFN))
 
 
+@unittest.skipIf(support.is_wasi, "WASI has no /dev/null")
 class DevNullTests(unittest.TestCase):
     def test_devnull(self):
         with open(os.devnull, 'wb', 0) as f:
@@ -2111,6 +2112,7 @@ def test_chmod(self):
         self.assertRaises(OSError, os.chmod, os_helper.TESTFN, 0)
 
 
+@unittest.skipIf(support.is_wasi, "Cannot create invalid FD on WASI.")
 class TestInvalidFD(unittest.TestCase):
     singles = ["fchdir", "dup", "fdatasync", "fstat",
                "fstatvfs", "fsync", "tcgetpgrp", "ttyname"]

Lib/test/test_pathlib.py

@@ -13,7 +13,7 @@
 from unittest import mock
 
 from test.support import import_helper
-from test.support import is_emscripten
+from test.support import is_emscripten, is_wasi
 from test.support import os_helper
 from test.support.os_helper import TESTFN, FakePath
 
@@ -1530,6 +1530,7 @@ def test_empty_path(self):
         p = self.cls('')
         self.assertEqual(p.stat(), os.stat('.'))
 
+    @unittest.skipIf(is_wasi, "WASI has no user accounts.")
     def test_expanduser_common(self):
         P = self.cls
         p = P('~')
@@ -2508,7 +2509,8 @@ def _check_symlink_loop(self, *args, strict=True):
             print(path.resolve(strict))
 
     @unittest.skipIf(
-        is_emscripten, "umask is not implemented on Emscripten."
+        is_emscripten or is_wasi,
+        "umask is not implemented on Emscripten/WASI."
     )
     def test_open_mode(self):
         old_mask = os.umask(0)
@@ -2534,7 +2536,8 @@ def test_resolve_root(self):
             os.chdir(current_directory)
 
     @unittest.skipIf(
-        is_emscripten, "umask is not implemented on Emscripten."
+        is_emscripten or is_wasi,
+        "umask is not implemented on Emscripten/WASI."
     )
     def test_touch_mode(self):
         old_mask = os.umask(0)

Lib/test/test_tarfile.py

@@ -1498,7 +1498,10 @@ def test_stream_padding(self):
 
     @unittest.skipUnless(sys.platform != "win32" and hasattr(os, "umask"),
                          "Missing umask implementation")
-    @unittest.skipIf(support.is_emscripten, "Emscripten's umask is a stub.")
+    @unittest.skipIf(
+        support.is_emscripten or support.is_wasi,
+        "Emscripten's/WASI's umask is a stub."
+    )
     def test_file_mode(self):
         # Test for issue #8464: Create files with correct
         # permissions.

Lib/test/test_unicode_file.py

@@ -110,7 +110,7 @@ def _test_single(self, filename):
             os.unlink(filename)
         self.assertTrue(not os.path.exists(filename))
         # and again with os.open.
-        f = os.open(filename, os.O_CREAT)
+        f = os.open(filename, os.O_CREAT | os.O_WRONLY)
         os.close(f)
         try:
             self._do_single(filename)

Tools/wasm/README.md

@@ -239,7 +239,11 @@ ## WASI limitations and issues (WASI SDK 15.0)
   yet. A future version of WASI may provide a limited ``set_permissions`` API.
 - File locking (``fcntl``) is not available.
 - ``os.pipe()``, ``os.mkfifo()``, and ``os.mknod()`` are not supported.
-- ``process_time`` clock does not work.
+- ``process_time`` does not work as expected because it's implemented using
+  wall clock.
+- ``os.umask`` is a stub.
+- ``sys.executable`` is empty.
+- ``/dev/null`` / ``os.devnull`` may not be available.
 
 
 # Detect WebAssembly builds