Fix os.path.sameopenfile for fake file descriptors

.pre-commit-config.yaml

@@ -1,5 +1,5 @@
 default_language_version:
-  python: "3.10"
+  python: "python3"
 
 repos:
   - repo: "https://github.com/asottile/pyupgrade"

CHANGES.md

@@ -13,6 +13,9 @@ The released versions correspond to PyPI releases.
 
 ### Fixes
 
+* fixed `os.path.sameopenfile` using real file descriptors instead of fake ones
+  (see [#1346](https://github.com/pytest-dev/pyfakefs/issues/1346))
+
 * fixed a crash if the stack limit was set to a low value
   (see [#1313](https://github.com/pytest-dev/pyfakefs/issues/1313))
 * fixed `os.ftruncate` to inspect the `FakeFileWrapper` returned by

pyfakefs/fake_os.py

@@ -1296,11 +1296,7 @@ def link(
             OSError:  if something already exists at new_path.
             OSError:  if the parent directory doesn't exist.
         """
-        if (
-            IS_PYPY
-            and not (self.filesystem.is_windows_fs and sys.version_info >= (3, 11))
-            and follow_symlinks is not None
-        ):
+        if IS_PYPY and sys.version_info < (3, 11) and follow_symlinks is not None:
             raise OSError(errno.EINVAL, "Invalid argument: follow_symlinks")
         if follow_symlinks is None:
             follow_symlinks = True

pyfakefs/fake_path.py

@@ -100,6 +100,7 @@ def dir() -> list[str]:
             "split",
             "splitdrive",
             "samefile",
+            "sameopenfile",
         ]
         if sys.version_info >= (3, 12):
             dir_list += ["isjunction", "splitroot"]
@@ -389,6 +390,18 @@ def samefile(self, path1: AnyStr, path2: AnyStr) -> bool:
         stat2 = self.filesystem.stat(path2)
         return stat1.st_ino == stat2.st_ino and stat1.st_dev == stat2.st_dev
 
+    def sameopenfile(self, fd1: int, fd2: int) -> bool:
+        """Return whether two file descriptors refer to the same file.
+
+        Args:
+            fd1: First open file descriptor.
+            fd2: Second open file descriptor.
+
+        Raises:
+            OSError: If either file descriptor is invalid.
+        """
+        return self._os_path.samestat(self.os.fstat(fd1), self.os.fstat(fd2))
+
     @overload
     def _join_real_path(
         self, path: str, rest: str, seen: dict[str, str | None]

pyfakefs/tests/fake_filesystem_test.py

@@ -1110,6 +1110,36 @@ def test_samefile(self):
         self.assertTrue(self.path.samefile(file_path1, "!foo!..!foo!bar!..!bar!baz"))
         self.assertTrue(self.path.samefile(file_path1, b"!foo!..!foo!bar!..!bar!baz"))
 
+    def test_sameopenfile(self):
+        def check_sameopenfile(path_module, open_file, file_path1, file_path2):
+            with open_file(file_path1) as first, open_file(file_path1) as second:
+                first_fd, second_fd = first.fileno(), second.fileno()
+                self.assertTrue(path_module.sameopenfile(first_fd, second_fd))
+                self.assertTrue(path_module.sameopenfile(first_fd, first_fd))
+                with open_file(file_path2) as other:
+                    self.assertFalse(path_module.sameopenfile(first_fd, other.fileno()))
+
+            with self.assertRaises(OSError) as error:
+                path_module.sameopenfile(first_fd, second_fd)
+            self.assertEqual(error.exception.errno, errno.EBADF)
+
+        file_path1 = "!foo!bar"
+        file_path2 = "!foo!baz"
+        fake_file_open = fake_open.FakeFileOpen(self.filesystem)
+        for os_type in OSType:
+            with self.subTest(os_type=os_type):
+                self.filesystem.os = os_type
+                self.filesystem.create_file(file_path1)
+                self.filesystem.create_file(file_path2)
+                check_sameopenfile(self.path, fake_file_open, file_path1, file_path2)
+
+        with tempfile.TemporaryDirectory() as real_dir:
+            real_file1 = os.path.join(real_dir, "bar")
+            real_file2 = os.path.join(real_dir, "baz")
+            with open(real_file1, "w"), open(real_file2, "w"):
+                pass
+            check_sameopenfile(os.path, open, real_file1, real_file2)
+
     def test_exists(self):
         file_path = "foo!bar!baz"
         file_path_bytes = b"foo!bar!baz"

pyfakefs/tests/fake_os_test.py

@@ -2772,7 +2772,10 @@ def test_link_count1(self):
         self.os.unlink(file1_path)
         self.assertEqual(self.os.stat(file2_path).st_nlink, 1)
 
-    @unittest.skipIf(IS_PYPY, "follow_symlinks not supported in PyPi")
+    @unittest.skipIf(
+        IS_PYPY and sys.version_info < (3, 11),
+        "follow_symlinks not supported in PyPy before Python 3.11",
+    )
     def test_link_no_follow_symlink(self):
         skip_if_symlink_not_supported()
         target_path = self.make_path("target_path")
@@ -2783,8 +2786,10 @@ def test_link_no_follow_symlink(self):
         self.os.link(symlink_path, link_path, follow_symlinks=False)
         self.assertTrue(self.os.path.islink(link_path))
 
-    @unittest.skipIf(not IS_PYPY, "follow_symlinks only not supported in PyPi")
-    @unittest.skipIf(IS_WIN, "supported in PyPy 3.11 under Windows")
+    @unittest.skipIf(
+        not IS_PYPY or IS_WIN or sys.version_info >= (3, 11),
+        "follow_symlinks only unsupported in PyPy before Python 3.11 on POSIX",
+    )
     def test_link_follow_symlink_not_supported_inPypy(self):
         skip_if_symlink_not_supported()
         target_path = self.make_path("target_path")