Python: Fix duplicate arguments in declaration-only tool streaming

[kartikmadan11]

Motivation & Context

When streaming declaration-only function calls, the final response contains duplicated arguments.

Fixes #6973

Description & Review Guide

What are the major changes?

• Modified _process_function_requests() in _tools.py (line 2403) to filter out function_call type items from the streamed result update
• Added two test cases covering chunked and single-chunk streaming scenarios

What is the impact?

• Eliminates argument duplication for declaration-only streaming tool calls
• Preserves correct behavior for function_result and approval items

Root Cause: The _stream() loop yields function_call chunks as they arrive, then later re-yields those same items from function_call_results. The _process_update() callback concatenates arguments with +=, so duplicate yields cause duplication.

Solution: Filter out function_call type items from the result's function_call_results before yielding, since they were already emitted by the inner stream.

Tests Added

• test_declaration_only_tool_streaming_no_argument_duplication() - Verifies multi-chunk streaming
• test_declaration_only_tool_streaming_single_chunk_no_duplication() - Verifies single-chunk streaming

Both tests pass ✅

[Copilot]

Pull request overview

Fixes a Python streaming bug in the core function-invocation layer where declaration-only tool calls could end up with duplicated arguments in the final aggregated response due to the same function_call content being yielded twice during streaming.

Changes:

• Filters function_call items out of the post-processing streamed function_call_results update to prevent _process_update from concatenating the same arguments twice.
• Adds regression tests for both multi-chunk and single-chunk streaming declaration-only tool calls.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 1 comment.

File	Description
python/packages/core/agent_framework/_tools.py	Adjusts streaming post-processing to avoid re-emitting function_call items that were already emitted by the inner stream.
python/packages/core/tests/core/test_function_invocation_logic.py	Adds tests ensuring declaration-only tool streaming does not duplicate function-call arguments.

[kartikmadan11]

Great catch, Copilot! I've addressed the concern about empty updates.

The fix:
When the filtered function_call_results list is empty (after excluding already-streamed function_call items), we now clear update_role to suppress the update. This prevents emitting confusing empty ChatResponseUpdate events.

Implementation:

• Filter out function_call items: filtered_results = [r for r in function_call_results if r.type != "function_call"]
• If the filtered list is empty, set result["update_role"] = None
• The existing yield check if role := result.get("update_role") will skip the empty update

This way declaration-only tools in streaming mode won't emit spurious empty updates—only the already-streamed chunks and any results/approvals will be emitted.

[moonbox3]

Could we preserve the finalized declaration-only call’s control metadata here? The earlier chunks contain the arguments, but user_input_request=True and id are added later to function_call_results. Filtering the finalized call entirely means streaming workflows never receive that signal, so AgentExecutor cannot emit request_info or pause for the client-side tool. Could the streaming path suppress only the duplicated arguments while retaining the finalized metadata?