Use importlib.util.find_spec to check if lm_eval is installed ins…

…tead of trying to import it (#1023)

Use importlib.util.find_spec to check if lm_eval is installed instead of trying to import it

There is a circular dependency when trying to import lm_eval inside torchao. The chain is like this:

torchao -> lm_eval -> transformers.pipelines -> torchao

And results in the following error:

RuntimeError: Failed to import transformers.pipelines because of the following error (look up to see its traceback):
cannot import name 'quantize_' from partially initialized module 'torchao.quantization'

which

1. causes _lm_eval_available to be erroneously set to False, even if lm_eval is available
2. interrupts lm_eval's initialization, leaving it partially initialized

you can observe this with:

>>> import torchao
>>> import lm_eval.__main__
>>> import lm_eval.api.registry
>> lm_eval.api.registry
AttributeError: module 'lm_eval' has no attribute 'api'

Having a bare except clause here was suppressing this circular import error, which from glancing around seems kind of like a general pattern in this code base. It might be worth reconsidering this pattern.

torchao/quantization/utils.py

@@ -3,7 +3,8 @@
 
 # This source code is licensed under the license found in the
 # LICENSE file in the root directory of this source tree.
-from typing import Dict, List, Optional, Tuple
+import importlib.util
+from typing import Dict, List, Optional
 
 import torch
 from torch.utils._python_dispatch import TorchDispatchMode
@@ -40,12 +41,7 @@
     "recommended_inductor_config_setter"
 ]
 
-try:
-    import lm_eval  # pyre-ignore[21]  # noqa: F401
-
-    _lm_eval_available = True
-except:
-    _lm_eval_available = False
+_lm_eval_available = importlib.util.find_spec("lm_eval") is not None
 
 # basic SQNR
 def compute_error(x, y):