issue27186: add open/io.open; patch by Jelle Zijlstra

Lib/_pyio.py

@@ -161,6 +161,8 @@ def open(file, mode="r", buffering=-1, encoding=None, errors=None,
     opened in a text mode, and for bytes a BytesIO can be used like a file
     opened in a binary mode.
     """
+    if not isinstance(file, int):
+        file = os.fspath(file)
     if not isinstance(file, (str, bytes, int)):
         raise TypeError("invalid file: %r" % file)
     if not isinstance(mode, str):

Lib/test/test_io.py

@@ -844,6 +844,32 @@ class IOTest(unittest.TestCase):
                 self.assertEqual(getattr(stream, method)(buffer), 5)
                 self.assertEqual(bytes(buffer), b"12345")
 
+    def test_fspath_support(self):
+        class PathLike:
+            def __init__(self, path):
+                self.path = path
+
+            def __fspath__(self):
+                return self.path
+
+        def check_path_succeeds(path):
+            with self.open(path, "w") as f:
+                f.write("egg\n")
+
+            with self.open(path, "r") as f:
+                self.assertEqual(f.read(), "egg\n")
+
+        check_path_succeeds(PathLike(support.TESTFN))
+        check_path_succeeds(PathLike(support.TESTFN.encode('utf-8')))
+
+        bad_path = PathLike(TypeError)
+        with self.assertRaisesRegex(TypeError, 'invalid file'):
+            self.open(bad_path, 'w')
+
+        # ensure that refcounting is correct with some error conditions
+        with self.assertRaisesRegex(ValueError, 'read/write/append mode'):
+            self.open(PathLike(support.TESTFN), 'rwxa')
+
 
 class CIOTest(IOTest):