Handle missing validation_ds in RNNT BPE transcribe

nemo/collections/asr/models/rnnt_bpe_models.py

@@ -528,6 +528,7 @@ def _setup_transcribe_dataloader(self, config: Dict) -> 'torch.utils.data.DataLo
             manifest_filepath = os.path.join(config['temp_dir'], 'manifest.json')
             batch_size = min(config['batch_size'], len(config['paths2audio_files']))
 
+        validation_ds = self.cfg.get('validation_ds') or {}
         dl_config = {
             'use_lhotse': config.get('use_lhotse', True),
             'manifest_filepath': manifest_filepath,
@@ -537,7 +538,7 @@ def _setup_transcribe_dataloader(self, config: Dict) -> 'torch.utils.data.DataLo
             'num_workers': config.get('num_workers', min(batch_size, os.cpu_count() - 1)),
             'pin_memory': True,
             'channel_selector': config.get('channel_selector', None),
-            'use_start_end_token': self.cfg.validation_ds.get('use_start_end_token', False),
+            'use_start_end_token': validation_ds.get('use_start_end_token', False),
         }
 
         if config.get("augmentor"):

tests/collections/asr/test_asr_rnnt_encoder_model_bpe.py

@@ -20,7 +20,7 @@
 import torch
 from lhotse import CutSet, MonoCut
 from lhotse.testing.dummies import DummyManifest
-from omegaconf import DictConfig
+from omegaconf import DictConfig, open_dict
 
 from nemo.collections.asr.data.audio_to_text_lhotse import LhotseSpeechToTextBpeDataset
 from nemo.collections.asr.models import ASRModel
@@ -194,6 +194,31 @@ def test_predict_step(self, asr_model):
         assert isinstance(outputs[0][0], MonoCut)
         assert isinstance(outputs[0][1], Hypothesis)
 
+    @pytest.mark.unit
+    def test_transcribe_dataloader_allows_missing_validation_ds(self, asr_model, monkeypatch):
+        """Some pretrained RNNT BPE checkpoints are shipped without validation_ds."""
+        with open_dict(asr_model.cfg):
+            asr_model.cfg.validation_ds = None
+        captured = {}
+
+        def capture_dataloader_config(config):
+            captured["config"] = config
+            return object()
+
+        monkeypatch.setattr(asr_model, "_setup_dataloader_from_config", capture_dataloader_config)
+
+        with tempfile.TemporaryDirectory() as tmpdir:
+            dataloader = asr_model._setup_transcribe_dataloader(
+                {
+                    "paths2audio_files": ["audio.wav"],
+                    "batch_size": 1,
+                    "temp_dir": tmpdir,
+                }
+            )
+
+        assert dataloader is not None
+        assert captured["config"]["use_start_end_token"] is False
+
     @pytest.mark.with_downloads()
     @pytest.mark.skipif(
         not NUMBA_RNNT_LOSS_AVAILABLE,