[gaurav-singh2525]

🛠 Summary

Issue: Fixes #4714

Problem

In src/http_frontend/http_graph_executor_impl.cpp, onPacketReadySerializeImpl() called packet.Get<std::string>() directly without checking !packet.IsEmpty() or validating the stored type. This triggered MediaPipe's internal ABSL_CHECK assertions, resulting in a fatal SIGABRT crash on empty or non-string packets.

Solution

1. Added packet.IsEmpty() validation: Safely clears the response and returns StatusCode::OK when empty/control packets arrive.
2. Added packet.ValidateAsType<std::string>().ok() validation: Safely returns StatusCode::MEDIAPIPE_EXECUTION_ERROR on type mismatch instead of triggering an uncatchable assertion abort.
3. Added #include "../logging.hpp": Provides proper debug and error logging when invalid packets are received.
4. Added Unit Tests: Added HttpMediapipeSerialization test suite in src/test/mediapipeflow_test.cpp verifying valid string extraction, empty packet handling, and error handling on incompatible types

🧪 Checklist

• Unit tests added.
• The documentation updated.
• Change follows security best practices.

[Copilot]

🟢 Approval recommended

No active review issues remain for the HTTP packet-serialization safeguards.

No open issues 🎉

What changed in this PR

Addresses #4714 by guarding HTTP MediaPipe packet serialization against empty and non-string payloads, preventing fatal assertions during string extraction.

Changes:

• Clears the response and returns success for empty packets.
• Logs type mismatches and returns MEDIAPIPE_EXECUTION_ERROR for non-string packets.
• Adds unit tests covering valid strings, empty packets, and incompatible payload types.

File	Description
src/​test/​mediapipeflow_test.cpp	Adds three tests for HTTP packet serialization behavior.
src/​http_frontend/​http_graph_executor_impl.cpp	Validates packets before string extraction and adds diagnostic logging.

_{Review effort: Balanced}