[BUG] promptflow 1.11.0 raises IndexError: list index out of range

[marinaby]

Describe the bug
When running a promptflow which calls a second promptflow as a function, we get the following error message:
IndexError: list index out of range

../..//lib/python3.9/site-packages/promptflow/_sdk/entities/_flows/base.py:239: in call
result = self.invoke(inputs=kwargs)
../..//lib/python3.9/site-packages/promptflow/_sdk/entities/_flows/dag.py:170: in invoke
return super().invoke(inputs=inputs)
../..//lib/python3.9/site-packages/promptflow/_sdk/entities/_flows/base.py:247: in invoke
result = invoker._invoke(
../..//lib/python3.9/site-packages/promptflow/core/_serving/flow_invoker.py:207: in _invoke
return self.executor.exec_line(data, run_id=run_id, allow_generator_output=self.streaming())
../..//lib/python3.9/site-packages/promptflow/executor/flow_executor.py:741: in exec_line
line_result = self._exec(
../../lib/python3.9/site-packages/promptflow/executor/flow_executor.py:1027: in _exec
output, aggregation_inputs = self._exec_inner_with_trace(
../..//lib/python3.9/site-packages/promptflow/executor/flow_executor.py:934: in _exec_inner_with_trace
self._exec_post_process(inputs, output, nodes_outputs, run_info, run_tracker, span, stream)
../..//lib/python3.9/site-packages/promptflow/executor/flow_executor.py:965: in _exec_post_process
run_tracker.update_and_persist_generator_node_runs(run_info.run_id, generator_output_nodes)

---

self = <promptflow._core.run_tracker.RunTracker object at 0x7fc19063ac10>
run_id = 'f5e974a5-d55f-4208-be32-502c38d1ba9e'
node_names = ['chat_with_context', 'post_process']
def update_and_persist_generator_node_runs(self, run_id: str, node_names: List[str]):
"""
Persists the node runs for nodes producing generators.

    :param run_id: The ID of the flow run.
    :type run_id: str
    :param node_names: The names of the nodes to persist.
    :type node_names: List[str]
    :returns: None
    """
    selected_node_run_info = (
        run_info for run_info in self.collect_child_node_runs(run_id) if run_info.node in node_names
    )
    for node_run_info in selected_node_run_info:
        # Update the output of the node run with the output in the trace.
        # This is because the output in the trace would includes the generated items.

      output_in_trace = node_run_info.api_calls[0]["output"]

E IndexError: list index out of range
../..//lib/python3.9/site-packages/promptflow/_core/run_tracker.py:452: IndexError

How To Reproduce the bug
Steps to reproduce the behavior, how frequent can you experience the bug:

1. Create a promptflow which invokes a second flows like this
   second_flow = promptflow.load_flow(flow_path)
   second_flow()
2. Invoke the (first) promptflow.

Expected behavior
The flow should succeed.

Running Information(please complete the following information):

• Promptflow Package Version: 1.11.0
• Operating System: macos
• Python Version using 3.9.18

Additional context
This issue started after upgrading promptflow to 1.11.0 version, in version 1.10.0 we didn't have this problem.

[D-W-]

Hi @marinaby , thanks for reporting, we are fixing this bug in attached PR. I'll update here once it got released. Please pin back to 1.10.0 before next release. Thanks!

[github-actions]

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