Support __fspath__() protocol on Windows

Test also non-ASCII mode.

Author: vstinner

Lib/test/test_capi/test_file.py

@@ -9,14 +9,23 @@
 class CAPIFileTest(unittest.TestCase):
     def test_py_fopen(self):
         # Test Py_fopen() and Py_fclose()
+        class FSPath:
+            def __init__(self, path):
+                self.path = path
+            def __fspath__(self):
+                return self.path
+
+        with open(__file__, "rb") as fp:
+            source = fp.read()
+
         for filename in (__file__, os.fsencode(__file__)):
             with self.subTest(filename=filename):
-                content = _testcapi.py_fopen(filename, "rb")
-                with open(filename, "rb") as fp:
-                    self.assertEqual(fp.read(256), content)
+                data = _testcapi.py_fopen(filename, "rb")
+                self.assertEqual(data, source[:256])
+
+                data = _testcapi.py_fopen(FSPath(filename), "rb")
+                self.assertEqual(data, source[:256])
 
-        with open(__file__, "rb") as fp:
-            content = fp.read()
         for filename in (
             os_helper.TESTFN,
             os.fsencode(os_helper.TESTFN),
@@ -26,11 +35,10 @@ def test_py_fopen(self):
             with self.subTest(filename=filename):
                 try:
                     with open(filename, "wb") as fp:
-                        fp.write(content)
+                        fp.write(source)
 
-                    content = _testcapi.py_fopen(filename, "rb")
-                    with open(filename, "rb") as fp:
-                        self.assertEqual(fp.read(256), content[:256])
+                    data = _testcapi.py_fopen(filename, "rb")
+                    self.assertEqual(data, source[:256])
                 finally:
                     os_helper.unlink(filename)
 
@@ -40,10 +48,15 @@ def test_py_fopen(self):
         with self.assertRaises(ValueError):
             _testcapi.py_fopen(b"a\x00b", "rb")
 
+        # non-ASCII mode failing with "Invalid argument"
+        with self.assertRaises(OSError):
+            _testcapi.py_fopen(__file__, "\xe9")
+
+        # invalid filename type
         for invalid_type in (123, object()):
             with self.subTest(filename=invalid_type):
                 with self.assertRaises(TypeError):
-                    _testcapi.py_fopen(invalid_type, "r")
+                    _testcapi.py_fopen(invalid_type, "rb")
 
         if support.MS_WINDOWS:
             with self.assertRaises(OSError):

Python/fileutils.c

@@ -1776,6 +1776,12 @@ Py_fopen(PyObject *path, const char *mode)
     int async_err = 0;
     int saved_errno;
 #ifdef MS_WINDOWS
+    PyObject *fspath = PyOS_FSPath(arg);
+    if (fspath == NULL) {
+        return NULL;
+    }
+    Py_SETREF(path, fspath);
+
     if (PyUnicode_Check(path)) {
         wchar_t *wpath = PyUnicode_AsWideCharString(path, NULL);
         if (wpath == NULL) {