set_dir expanding "~"

Fixes pytorch#69761.

Small change to torch.hub.set_dir() (<10 LOC).

It seems that before the code was split into `set_dir()` and `_get_torch_home `, an [earlier version](https://github.com/pytorch/pytorch/blame/5164622ba462fe07fc9f2325fccf7f85aecb3ec8/torch/hub.py#L111) of hub.py had a os.path.expanduser check.

Currently, [_get_torch_home](https://github.com/pytorch/pytorch/blob/master/torch/hub.py#L104) retained the os.path.expanduser check, but `set_dir()` didn't have one. This PR fixes that (I hope).

(As I mentioned in the issue, I can't run the tests on my laptop yet because of storage space :/ But I did include a test.)
Pull Request resolved: pytorch#69763
Approved by: https://github.com/malfet, https://github.com/NicolasHug

test/test_utils.py

@@ -628,6 +628,13 @@ def test_get_set_dir(self):
             self.assertEqual(sum_of_state_dict(hub_model.state_dict()), SUM_OF_HUB_EXAMPLE)
             assert os.path.exists(os.path.join(tmpdir, 'ailzhang_torchhub_example_master'))
 
+        # Test that set_dir properly calls expanduser()
+        # non-regression test for https://github.com/pytorch/pytorch/issues/69761
+        new_dir = os.path.join("~", "hub")
+        torch.hub.set_dir(new_dir)
+        self.assertEqual(torch.hub.get_dir(), os.path.expanduser(new_dir))
+
+
     @retry(Exception, tries=3)
     def test_list_entrypoints(self):
         entry_lists = hub.list('ailzhang/torchhub_example', force_reload=True)

torch/hub.py

@@ -283,7 +283,7 @@ def set_dir(d):
         d (string): path to a local folder to save downloaded models & weights.
     """
     global _hub_dir
-    _hub_dir = d
+    _hub_dir = os.path.expanduser(d)
 
 
 def list(github, force_reload=False, skip_validation=False):