Add attribute access for some moved constants back to fake_filesystem

- some if these had been accessed in user code,
  which caused a regression
- add convenience function get_uid()/get_gid()
- see #809

8 files changed, 95 insertions, 13 deletions

diff --git a/CHANGES.md b/CHANGES.md
index 4278df7..797f085 100644
--- a/CHANGES.md
+++ b/CHANGES.md
@@ -3,9 +3,17 @@ The released versions correspond to PyPI releases.
 
 ## Unreleased
 
+### Changes
+* Made the user and group IDs accessible via dedicated ``get_uid`` and ``get_gid``
+  functions (for symmetry to ``set_uid`` / ``set_gid``)
+
 ### Fixes
 * The test fixture is now included in the source distribution and installed
   with the package.
+* Some public constants in `fake_filesystem` that had been moved to `helpers` are
+  made accessible from there again (see [#809](../../issues/809)).
+* Add missing fake implementations for `os.getuid` and `os.getgid` (Posix only)
+
 
 ## [Version 5.2.1](https://pypi.python.org/pypi/pyfakefs/5.2.1) (2023-04-11)
 Support for latest Python 3.12 version.
diff --git a/docs/modules.rst b/docs/modules.rst
index 420d7ec..75c96bf 100644
--- a/docs/modules.rst
+++ b/docs/modules.rst
@@ -7,7 +7,7 @@ Public Modules and Classes
 Fake filesystem module
 ----------------------
 .. automodule:: pyfakefs.helpers
-    :members: set_uid, set_gid, reset_ids, is_root
+    :members: get_uid, set_uid, get_gid, set_gid, reset_ids, is_root
 
 Fake filesystem classes
 -----------------------
diff --git a/pyfakefs/fake_file.py b/pyfakefs/fake_file.py
index 4158a0b..0a866b1 100644
--- a/pyfakefs/fake_file.py
+++ b/pyfakefs/fake_file.py
@@ -159,7 +159,10 @@ class FakeFile:
         self._side_effect: Optional[Callable] = side_effect
         self.name: AnyStr = name  # type: ignore[assignment]
         self.stat_result = FakeStatResult(
-            filesystem.is_windows_fs, helpers.USER_ID, helpers.GROUP_ID, helpers.now()
+            filesystem.is_windows_fs,
+            helpers.get_uid(),
+            helpers.get_gid(),
+            helpers.now(),
         )
         if st_mode >> 12 == 0:
             st_mode |= S_IFREG
diff --git a/pyfakefs/fake_filesystem.py b/pyfakefs/fake_filesystem.py
index 7a5c6b5..0b85e77 100644
--- a/pyfakefs/fake_filesystem.py
+++ b/pyfakefs/fake_filesystem.py
@@ -159,10 +159,19 @@ if sys.platform != "win32":
 PatchMode = fake_io.PatchMode
 
 is_root = helpers.is_root
+get_uid = helpers.get_uid
 set_uid = helpers.set_uid
+get_gid = helpers.get_gid
 set_gid = helpers.set_gid
 reset_ids = helpers.reset_ids
 
+PERM_READ = helpers.PERM_READ
+PERM_WRITE = helpers.PERM_WRITE
+PERM_EXE = helpers.PERM_EXE
+PERM_DEF = helpers.PERM_DEF
+PERM_DEF_FILE = helpers.PERM_DEF_FILE
+PERM_ALL = helpers.PERM_ALL
+
 
 class FakeFilesystem:
     """Provides the appearance of a real directory tree for unit testing.
@@ -735,7 +744,7 @@ class FakeFilesystem:
         times: Optional[Tuple[Union[int, float], Union[int, float]]] = None,
         *,
         ns: Optional[Tuple[int, int]] = None,
-        follow_symlinks: bool = True
+        follow_symlinks: bool = True,
     ) -> None:
         """Change the access and modified times of a file.
 
@@ -1620,10 +1629,10 @@ class FakeFilesystem:
 
     @staticmethod
     def _can_read(target, owner_can_read):
-        if target.st_uid == helpers.USER_ID:
+        if target.st_uid == helpers.get_uid():
             if owner_can_read or target.st_mode & 0o400:
                 return True
-        if target.st_gid == helpers.GROUP_ID:
+        if target.st_gid == get_gid():
             if target.st_mode & 0o040:
                 return True
         return target.st_mode & 0o004
@@ -2914,5 +2923,14 @@ def _run_doctest() -> TestResults:
     return doctest.testmod(pyfakefs.fake_filesystem)
 
 
+def __getattr__(name):
+    # backwards compatibility for read access to globals moved to helpers
+    if name == "USER_ID":
+        return helpers.USER_ID
+    if name == "GROUP_ID":
+        return helpers.GROUP_ID
+    raise AttributeError(f"No attribute {name!r}.")
+
+
 if __name__ == "__main__":
     _run_doctest()
diff --git a/pyfakefs/fake_os.py b/pyfakefs/fake_os.py
index 912fd31..a28939d 100644
--- a/pyfakefs/fake_os.py
+++ b/pyfakefs/fake_os.py
@@ -65,6 +65,8 @@ from pyfakefs.helpers import (
     PERM_EXE,
     PERM_DEF,
     is_root,
+    get_uid,
+    get_gid,
 )
 
 if TYPE_CHECKING:
@@ -134,6 +136,11 @@ class FakeOsModule:
                 "removexattr",
                 "setxattr",
             ]
+        if sys.platform != "win32":
+            _dir += [
+                "getgid",
+                "getuid",
+            ]
         if use_scandir:
             _dir += ["scandir"]
         return _dir
@@ -1272,6 +1279,22 @@ class FakeOsModule:
             return written
         return 0
 
+    def getuid(self) -> int:
+        """Returns the user id set in the fake filesystem.
+        If not changed using ``set_uid``, this is the uid of the real system.
+        """
+        if self.filesystem.is_windows_fs:
+            raise NameError("name 'getuid' is not defined")
+        return get_uid()
+
+    def getgid(self) -> int:
+        """Returns the group id set in the fake filesystem.
+        If not changed using ``set_gid``, this is the gid of the real system.
+        """
+        if self.filesystem.is_windows_fs:
+            raise NameError("name 'getgid' is not defined")
+        return get_gid()
+
     def fake_functions(self, original_functions) -> Set:
         functions = set()
         for fn in original_functions:
diff --git a/pyfakefs/helpers.py b/pyfakefs/helpers.py
index 8e32b3a..de4a62a 100644
--- a/pyfakefs/helpers.py
+++ b/pyfakefs/helpers.py
@@ -44,6 +44,11 @@ else:
     GROUP_ID = os.getgid()
 
 
+def get_uid() -> int:
+    """Get the global user id. Same as ``os.getuid()``"""
+    return USER_ID
+
+
 def set_uid(uid: int) -> None:
     """Set the global user id. This is used as st_uid for new files
     and to differentiate between a normal user and the root user (uid 0).
@@ -56,6 +61,11 @@ def set_uid(uid: int) -> None:
     USER_ID = uid
 
 
+def get_gid() -> int:
+    """Get the global group id. Same as ``os.getgid()``"""
+    return GROUP_ID
+
+
 def set_gid(gid: int) -> None:
     """Set the global group id. This is only used to set st_gid for new files,
     no permission checks are performed.
diff --git a/pyfakefs/tests/fake_filesystem_shutil_test.py b/pyfakefs/tests/fake_filesystem_shutil_test.py
index e1bfab1..a3b4ae3 100644
--- a/pyfakefs/tests/fake_filesystem_shutil_test.py
+++ b/pyfakefs/tests/fake_filesystem_shutil_test.py
@@ -25,7 +25,7 @@ import unittest
 from pathlib import Path
 
 from pyfakefs import fake_filesystem_unittest
-from pyfakefs.helpers import USER_ID, set_uid, is_root
+from pyfakefs.helpers import get_uid, set_uid, is_root
 from pyfakefs.tests.test_utils import RealFsTestMixin
 
 is_windows = sys.platform == "win32"
@@ -39,7 +39,7 @@ class RealFsTestCase(fake_filesystem_unittest.TestCase, RealFsTestMixin):
     def setUp(self):
         RealFsTestMixin.setUp(self)
         self.cwd = os.getcwd()
-        self.uid = USER_ID
+        self.uid = get_uid()
         set_uid(1000)
         if not self.use_real_fs():
             self.setUpPyfakefs()
diff --git a/pyfakefs/tests/fake_os_test.py b/pyfakefs/tests/fake_os_test.py
index dc83649..484443c 100644
--- a/pyfakefs/tests/fake_os_test.py
+++ b/pyfakefs/tests/fake_os_test.py
@@ -21,7 +21,7 @@ import stat
 import sys
 import unittest
 
-from pyfakefs.helpers import IN_DOCKER, IS_PYPY, GROUP_ID, USER_ID
+from pyfakefs.helpers import IN_DOCKER, IS_PYPY, get_uid, get_gid
 
 from pyfakefs import fake_filesystem, fake_os, fake_open, fake_file
 from pyfakefs.fake_filesystem import (
@@ -5403,6 +5403,26 @@ class FakeOsUnreadableDirTest(FakeOsModuleTestBase):
         else:
             self.os.chmod(path, mode)
 
+    def test_getuid(self):
+        self.skip_real_fs()  # won't change user in real fs
+        self.check_posix_only()
+        uid = self.os.getuid()
+        set_uid(uid + 10)
+        self.assertEqual(uid + 10, self.os.getuid())
+        self.assertEqual(uid + 10, get_uid())
+        set_uid(uid)
+        self.assertEqual(uid, self.os.getuid())
+
+    def test_getgid(self):
+        self.skip_real_fs()  # won't change group in real fs
+        self.check_posix_only()
+        gid = self.os.getgid()
+        set_gid(gid + 10)
+        self.assertEqual(gid + 10, self.os.getgid())
+        self.assertEqual(gid + 10, get_gid())
+        set_gid(gid)
+        self.assertEqual(gid, self.os.getgid())
+
     def test_listdir_unreadable_dir(self):
         if not is_root():
             self.assert_raises_os_error(errno.EACCES, self.os.listdir, self.dir_path)
@@ -5417,7 +5437,7 @@ class FakeOsUnreadableDirTest(FakeOsModuleTestBase):
     def test_listdir_user_readable_dir_from_other_user(self):
         self.skip_real_fs()  # won't change user in real fs
         self.check_posix_only()
-        user_id = USER_ID
+        user_id = get_uid()
         set_uid(user_id + 1)
         dir_path = self.make_path("dir1")
         self.create_dir(dir_path, perm=0o600)
@@ -5431,7 +5451,7 @@ class FakeOsUnreadableDirTest(FakeOsModuleTestBase):
 
     def test_listdir_group_readable_dir_from_other_user(self):
         self.skip_real_fs()  # won't change user in real fs
-        user_id = USER_ID
+        user_id = get_uid()
         set_uid(user_id + 1)
         dir_path = self.make_path("dir1")
         self.create_dir(dir_path, perm=0o660)
@@ -5442,7 +5462,7 @@ class FakeOsUnreadableDirTest(FakeOsModuleTestBase):
     def test_listdir_group_readable_dir_from_other_group(self):
         self.skip_real_fs()  # won't change user in real fs
         self.check_posix_only()
-        group_id = GROUP_ID
+        group_id = self.os.getgid()
         set_gid(group_id + 1)
         dir_path = self.make_path("dir1")
         self.create_dir(dir_path, perm=0o060)
@@ -5456,7 +5476,7 @@ class FakeOsUnreadableDirTest(FakeOsModuleTestBase):
 
     def test_listdir_other_readable_dir_from_other_group(self):
         self.skip_real_fs()  # won't change user in real fs
-        group_id = GROUP_ID
+        group_id = get_gid()
         set_gid(group_id + 1)
         dir_path = self.make_path("dir1")
         self.create_dir(dir_path, perm=0o004)
@@ -5489,7 +5509,7 @@ class FakeOsUnreadableDirTest(FakeOsModuleTestBase):
 
     def test_remove_unreadable_dir_from_other_user(self):
         self.skip_real_fs()  # won't change user in real fs
-        user_id = USER_ID
+        user_id = get_uid()
         set_uid(user_id + 1)
         dir_path = self.make_path("dir1")
         self.create_dir(dir_path, perm=0o000)