fix: improve error handling for unexpected prompt types and update stream test assertions

Author: Ki-Seki

outlines/models/llamacpp.py

@@ -300,6 +300,8 @@ def generate(
                 **inference_kwargs,
             )
             result = completion["choices"][0]["message"]["content"]
+        else:  # Never reached  # pragma: no cover
+            raise ValueError("Unexpected prompt type.")
 
         self.model.reset()
 
@@ -359,7 +361,8 @@ def generate_stream(
             )
             for chunk in generator:
                 yield chunk["choices"][0]["delta"].get("content", "")
-
+        else:  # Never reached  # pragma: no cover
+            raise ValueError("Unexpected prompt type.")
 
 def from_llamacpp(model: "Llama", chat_mode: bool = True) -> LlamaCpp:
     """Create an Outlines `LlamaCpp` model instance from a

tests/models/test_llamacpp.py

@@ -239,4 +239,5 @@ def test_llamacpp_no_chat(model_no_chat):
     assert isinstance(result, str)
 
     generator = model_no_chat.stream("Respond with one word. Not more.", None)
-    assert isinstance(next(generator), str)
+    for x in generator:
+        assert isinstance(x, str)