Fix behavior of fake os.makedirs

- use a similar implementation as the real fs

CHANGES.md

@@ -32,6 +32,7 @@ The released versions correspond to PyPI releases.
   (see [#979](../../issues/979))
 * fixed handling of errors on opening files via file descriptor (see [#967](../../issues/967))
 * fixed handling of `umask` - it is now applied by default
+* fixed behavior of `os.makedirs` (see [#987](../../issues/987))
 
 ### Infrastructure
 * replace `undefined` by own minimal implementation to avoid importing it

pyfakefs/fake_os.py

@@ -931,7 +931,27 @@ def makedirs(
         """
         if exist_ok is None:
             exist_ok = False
-        self.filesystem.makedirs(name, mode, exist_ok)
+
+        # copied and adapted from real implementation in os.py (Python 3.12)
+        head, tail = self.filesystem.splitpath(name)
+        if not tail:
+            head, tail = self.filesystem.splitpath(head)
+        if head and tail and not self.filesystem.exists(head):
+            try:
+                self.makedirs(head, exist_ok=exist_ok)
+            except FileExistsError:
+                pass
+            cdir = self.filesystem.cwd
+            if isinstance(tail, bytes):
+                if tail == bytes(cdir, "ASCII"):
+                    return
+            elif tail == cdir:
+                return
+        try:
+            self.mkdir(name, mode)
+        except OSError:
+            if not exist_ok or not self.filesystem.isdir(name):
+                raise
 
     def _path_with_dir_fd(
         self,

pyfakefs/tests/fake_os_test.py

@@ -1893,6 +1893,14 @@ def test_makedirs_raises_on_empty_path(self):
         self.assert_raises_os_error(errno.ENOENT, self.os.makedirs, "", exist_ok=False)
         self.assert_raises_os_error(errno.ENOENT, self.os.makedirs, "", exist_ok=True)
 
+    def test_makedirs_with_relative_paths(self):
+        # regression test for #987
+        path = self.make_path("base", "foo", "..", "bar")
+        self.os.makedirs(path)
+        self.assertTrue(self.os.path.isdir(self.make_path("base", "bar")))
+        self.assertTrue(self.os.path.isdir(self.make_path("base", "foo")))
+        self.assertFalse(self.os.path.isdir(self.make_path("base", "foo", "bar")))
+
     # test fsync and fdatasync
     def test_fsync_raises_on_non_int(self):
         with self.assertRaises(TypeError):