Non-Streaming Models Do Not Return Results Properly in _handle_invoke_result

[vasu-negi]

Fix: Non-Streaming Models Do Not Return Results Properly in _handle_invoke_result
Summary
This PR fixes an issue where models that do not support streaming (stream=False) fail to return results properly. The _handle_invoke_result function was not yielding any events when it received an LLMResult, leading to an empty generator. As a result, the for event in generator: loop in _run() never executed, causing missing responses for non-streaming models.

Issue:
Non-streaming models (stream=False) return an LLMResult, but _handle_invoke_result does not yield anything.
This causes _run() to receive an empty generator, resulting in no response being sent.
Streaming models (stream=True) work fine, as their results are handled iteratively.
Root Cause:
The _handle_invoke_result method contained this condition:

FIx #13569

if isinstance(invoke_result, LLMResult):
return # ❌ This exits without yielding any event
Since _handle_invoke_result did not yield an event for non-streaming models, the generator was empty.
_run() expects to iterate over generator, but since it was empty, the loop never executed.
Fix Implemented
The fix ensures _handle_invoke_result always yields a ModelInvokeCompletedEvent when stream=False, preventing an empty generator.

Updated _handle_invoke_result Implementation:

def _handle_invoke_result(self, invoke_result: LLMResult | Generator) -> Generator[NodeEvent, None, None]:

# Handle non-streaming models
if isinstance(invoke_result, LLMResult):
    yield ModelInvokeCompletedEvent(
        text=invoke_result.message.content,
        usage=invoke_result.usage,
        finish_reason=None,  # Adjust as needed
    )
    return  # Ensures at least one event is yielded

Impact of the Fix
✅ Non-streaming models now return responses correctly.
✅ Streaming models (stream=True) remain unaffected.
✅ Prevents missing responses by ensuring _handle_invoke_result always yields an event.

Testing & Validation
Verified that non-streaming models (stream=False) now return valid responses.
Ensured that streaming models (stream=True) function as expected.
Confirmed that _handle_invoke_result always yields at least one event, preventing an empty generator.

[crazywoola]

Please fix the lint errors

[vasu-negi]

Sure, will do

[vasu-negi]

@crazywoola I have fixed the lint issues, it does not complain in local, can we try running the pipeline

[vasu-negi]

i think my IDE is incorrectly formatting the idents, i am checking.

[vasu-negi]

@crazywoola i have fixed my code editor issue, can you please try again.

[crazywoola]

Next time you can run this cmd ./dev/reformat in root dir. :)

[laipz8200]

LGTM