[Wav2Vec2ProcessorWithLM] improve decoder downlaod (#15040)

src/transformers/models/wav2vec2_with_lm/processing_wav2vec2_with_lm.py

@@ -166,7 +166,14 @@ class Wav2Vec2ProcessorWithLM:
             # BeamSearchDecoderCTC has no auto class
             kwargs.pop("_from_auto", None)
 
-            decoder = BeamSearchDecoderCTC.load_from_hf_hub(pretrained_model_name_or_path, **kwargs)
+            # make sure that only relevant filenames are downloaded
+            language_model_filenames = os.path.join(BeamSearchDecoderCTC._LANGUAGE_MODEL_SERIALIZED_DIRECTORY, "*")
+            alphabet_filename = BeamSearchDecoderCTC._ALPHABET_SERIALIZED_FILENAME
+            allow_regex = [language_model_filenames, alphabet_filename]
+
+            decoder = BeamSearchDecoderCTC.load_from_hf_hub(
+                pretrained_model_name_or_path, allow_regex=allow_regex, **kwargs
+            )
 
         # set language model attributes
         for attribute in ["alpha", "beta", "unk_score_offset", "score_boundary"]:

tests/test_processor_wav2vec2_with_lm.py

@@ -18,6 +18,7 @@ import shutil
 import tempfile
 import unittest
 from multiprocessing import Pool
+from pathlib import Path
 
 import numpy as np
 
@@ -234,3 +235,16 @@ class Wav2Vec2ProcessorWithLMTest(unittest.TestCase):
 
         self.assertListEqual(decoded_decoder, decoded_processor)
         self.assertListEqual(["<s> </s> </s>", "<s> <s> </s>"], decoded_processor)
+
+    def test_decoder_download_ignores_files(self):
+        processor = Wav2Vec2ProcessorWithLM.from_pretrained("hf-internal-testing/processor_with_lm")
+
+        language_model = processor.decoder.model_container[processor.decoder._model_key]
+        path_to_cached_dir = Path(language_model._kenlm_model.path.decode("utf-8")).parent.parent.absolute()
+
+        downloaded_decoder_files = os.listdir(path_to_cached_dir)
+
+        # test that only decoder relevant files from
+        # https://huggingface.co/hf-internal-testing/processor_with_lm/tree/main
+        # are downloaded and none of the rest (e.g. README.md, ...)
+        self.assertListEqual(downloaded_decoder_files, ["alphabet.json", "language_model"])