Fix error in M4T feature extractor (#28340)

* fix M4T FE error when no attention mask

* modify logic

* add test

* go back to initial test situation + add other tests

src/transformers/models/seamless_m4t/feature_extraction_seamless_m4t.py

@@ -229,6 +229,10 @@ class SeamlessM4TFeatureExtractor(SequenceFeatureExtractor):
                 "Failing to do so can result in silent errors that might be hard to debug."
             )
 
+        return_attention_mask = (
+            return_attention_mask if return_attention_mask is not None else self.return_attention_mask
+        )
+
         is_batched_numpy = isinstance(raw_speech, np.ndarray) and len(raw_speech.shape) > 1
         if is_batched_numpy and len(raw_speech.shape) > 3:
             raise ValueError(f"Only mono-channel or stereo-channel audio is supported for input to {self}")
@@ -270,13 +274,13 @@ class SeamlessM4TFeatureExtractor(SequenceFeatureExtractor):
             max_length=max_length,
             truncation=truncation,
             pad_to_multiple_of=pad_to_multiple_of,
-            return_attention_mask=return_attention_mask,
+            return_attention_mask=True,
             return_tensors="np",
         )
 
         # SeamlessM4T needs to process extracted features
         input_features = padded_inputs.get("input_features")
-        attention_mask = padded_inputs.get("attention_mask")
+        attention_mask = padded_inputs.pop("attention_mask")
 
         batch_size, num_frames, num_channels = input_features.shape
 
@@ -293,7 +297,8 @@ class SeamlessM4TFeatureExtractor(SequenceFeatureExtractor):
         attention_mask = attention_mask[:, indices % self.stride == 1]
 
         padded_inputs["input_features"] = input_features
-        padded_inputs["attention_mask"] = attention_mask
+        if return_attention_mask:
+            padded_inputs["attention_mask"] = attention_mask
 
         if return_tensors is not None:
             padded_inputs = padded_inputs.convert_to_tensors(return_tensors)

tests/models/seamless_m4t/test_feature_extraction_seamless_m4t.py

@@ -171,6 +171,42 @@ class SeamlessM4TFeatureExtractionTest(SequenceFeatureExtractionTestMixin, unitt
         for enc_seq_1, enc_seq_2 in zip(encoded_sequences_1, encoded_sequences_2):
             self.assertTrue(np.allclose(enc_seq_1, enc_seq_2, atol=1e-3))
 
+    def test_call_without_attention_mask(self):
+        feature_extractor_args = self.feat_extract_tester.prepare_feat_extract_dict()
+        feature_extractor = self.feature_extraction_class(**feature_extractor_args)
+
+        # create three inputs of length 800, 1000, and 1200
+        speech_inputs = [floats_list((1, x))[0] for x in range(800, 1400, 200)]
+        np_speech_inputs = [np.asarray(speech_input) for speech_input in speech_inputs]
+
+        # Test attention mask when passing no attention mask to forward call
+        output = feature_extractor(np_speech_inputs, padding=True, return_tensors="np", return_attention_mask=False)
+        self.assertTrue("attention_mask" not in output)
+
+        # Test attention mask when no attention mask by default
+        feature_extractor_args["return_attention_mask"] = False
+        feature_extractor = self.feature_extraction_class(**feature_extractor_args)
+        output = feature_extractor(np_speech_inputs, padding=True, return_tensors="np", return_attention_mask=False)
+        self.assertTrue("attention_mask" not in output)
+
+    def test_attention_mask(self):
+        # test attention mask has the right output shape
+        feature_extractor_args = self.feat_extract_tester.prepare_feat_extract_dict()
+
+        feature_extractor = self.feature_extraction_class(**feature_extractor_args)
+        # create three inputs of length 800, 1000, and 1200
+        speech_inputs = [floats_list((1, x))[0] for x in range(800, 1400, 200)]
+        np_speech_inputs = [np.asarray(speech_input) for speech_input in speech_inputs]
+
+        # Test attention mask when passing it to forward call
+        output = feature_extractor(np_speech_inputs, padding=True, return_tensors="np")
+        input_features = output.input_features
+
+        attention_mask = output.attention_mask
+        self.assertTrue(attention_mask.ndim == 2)
+        self.assertTrue(attention_mask.shape[0] == 3)
+        self.assertTrue(attention_mask.shape[-1] == input_features.shape[1])
+
     @require_torch
     def test_call_torch(self):
         import torch