Auto feature extractor (#11097)

* AutoFeatureExtractor

* Init and first tests

* Tests

* Damn you gitignore

* Quality

* Defensive test for when not all backends are here

* Use pattern for Speech2Text models

tests/test_feature_extraction_auto.py

@@ -0,0 +1,44 @@
+# coding=utf-8
+# Copyright 2021 the HuggingFace Inc. team.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+import os
+import unittest
+
+from transformers import FEATURE_EXTRACTOR_MAPPING, AutoFeatureExtractor, Wav2Vec2FeatureExtractor
+
+
+SAMPLE_FEATURE_EXTRACTION_CONFIG = os.path.join(
+    os.path.dirname(os.path.abspath(__file__)), "fixtures/dummy_feature_extractor_config.json"
+)
+
+
+class AutoFeatureExtractorTest(unittest.TestCase):
+    def test_feature_extractor_from_model_shortcut(self):
+        config = AutoFeatureExtractor.from_pretrained("facebook/wav2vec2-base-960h")
+        self.assertIsInstance(config, Wav2Vec2FeatureExtractor)
+
+    def test_feature_extractor_from_local_file(self):
+        config = AutoFeatureExtractor.from_pretrained(SAMPLE_FEATURE_EXTRACTION_CONFIG)
+        self.assertIsInstance(config, Wav2Vec2FeatureExtractor)
+
+    def test_pattern_matching_fallback(self):
+        """
+        In cases where config.json doesn't include a model_type,
+        perform a few safety checks on the config mapping's order.
+        """
+        # no key string should be included in a later key string (typical failure case)
+        keys = list(FEATURE_EXTRACTOR_MAPPING.keys())
+        for i, key in enumerate(keys):
+            self.assertFalse(any(key in later_key for later_key in keys[i + 1 :]))