Normalize asset paths before looking them up in the asset dict.

PiperOrigin-RevId: 809702931
Change-Id: Iffccdd8d87b818b87797bd3570888a0e8e423815

Author: Adrian Collister

dm_control/mjcf/attribute.py

@@ -536,7 +536,9 @@ def _get_asset_from_path(self, path):
       base_path = self._parent.namescope.get(
           constants.BASEPATH, constants.ASSETDIR_NAMESPACE
       )
-    full_path = os.path.join(base_path, path) if base_path else path
+    full_path = (
+        os.path.normpath(os.path.join(base_path, path)) if base_path else path
+    )
 
     # Look in the dict of pre-loaded assets before checking the filesystem.
     if path in self._parent.namescope.assets:

dm_control/mjcf/attribute_test.py

@@ -456,9 +456,9 @@ def testFileFromAssetsDict(self):
   def testFileFromAssetsDictWithBasepath(self):
     prefix = 'fake_filename'
     extension = '.whatever'
-    path = 'invalid/path/' + prefix + extension
+    path = 'invalid/../path/' + prefix + extension
     contents = 'Fake contents'
-    assets = {os.path.join(ASSETS_DIR, path): contents}
+    assets = {os.path.normpath(os.path.join(ASSETS_DIR, path)): contents}
     mujoco = element.RootElement(assets=assets)
     mujoco.files.text_path = ASSETS_DIR
     text_file = mujoco.files.add('text', file=path)