[Bugfix] Fix fallback loading for IndexTTS external models (#6137)

Signed-off-by: boatman <109857087+sphinxkkkbc@users.noreply.github.com>

tests/model_executor/models/indextts2/test_enhanced_codec.py

@@ -82,3 +82,31 @@ def test_model_asset_resolver_supports_native_checkpoints_layout(tmp_path):
     checkpoint.touch()
 
     assert preprocess_utils.resolve_model_file(str(tmp_path), "codec.pth") == str(checkpoint)
+
+
+def test_campplus_falls_back_to_hub_for_local_model_dir(tmp_path, monkeypatch):
+    import huggingface_hub
+
+    from vllm_omni.model_executor.models.indextts2.utils.campplus import dtdnn
+
+    checkpoint = tmp_path / "downloaded-campplus.bin"
+    checkpoint.touch()
+    downloads = []
+
+    class FakeCAMPPlus(torch.nn.Module):
+        def load_state_dict(self, state, strict=True):
+            self.loaded_state = (state, strict)
+
+    monkeypatch.setattr(dtdnn, "CAMPPlus", lambda **_kwargs: FakeCAMPPlus())
+    monkeypatch.setattr(
+        huggingface_hub,
+        "hf_hub_download",
+        lambda repo_id, filename: downloads.append((repo_id, filename)) or str(checkpoint),
+    )
+    monkeypatch.setattr(preprocess_utils.torch, "load", lambda *_args, **_kwargs: {"weight": torch.ones(1)})
+    preprocess_utils._campplus_cache.clear()
+
+    model = preprocess_utils.load_campplus(str(tmp_path), torch.device("cpu"))
+
+    assert isinstance(model, FakeCAMPPlus)
+    assert downloads == [("funasr/campplus", "campplus_cn_common.bin")]