ArduPilot/ardupilot

handle_mission_write_partial_list is too strict

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#4,889 opened on Sep 25, 2016

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AllVehiclesLibraryMAVLinkgood first issue

Description

Issue details

Currently GCSCommon.cpp@handle_mission_write_partial_list checks if the partial waypoint list is inside the current mission count boundary unnecessarily. This limits the utility of partial waypoint writing modifications because we can never expand the mission count.

A very simple case is appending a waypoint to a waypoint list. As far as I know a full rewrite of the mission plan would be required because the only other way to change the waypoint list is sending a mavlink_msg_mission_count* message with the previous mission count plus one. This is exactly what a partial list is for.

Removing the upper bound checks would not result in a problem because GCS_Common.cpp@GCS_MAVLINK::handle_mission_item:839 already handles the case where the mission seq is bigger than mission.num_commands().

Am I wrong in these assumptions? If theoretically there is no problem I can produce a patch removing the upper bound checks.

Contributor guide

Tech stack
cpp
Domain
backend
Issue type
bug
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
3
Estimated timeA rough time range for an experienced contributor to investigate, implement, test, and prepare a pull request.
1-3 hours
Activity statusHow available the issue appears right now: fresh, active, stale, blocked, or waiting on maintainer input.
stale
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
clear
Prerequisites
basic C++ knowledgeMAVLink mission protocol overview
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
45
Research direction
The issue proposes removing upper bound checks in `GCSCommon.cpp`'s `handle mission write partial list`. Review the referenced file and function to understand the current logic. Also examine `GCS Common.cpp` line 839 to confirm that handling of out of range mission seq is already safe. Consider writing a simple patch and testing with a mission count increase scenario. There are 3 comments on the issue; read them for additional context. The fix is localized and well documented.
handle_mission_write_partial_list is too strict · ArduPilot/ardupilot#4889 | Good First Issue