luanti-org/luanti

VoxelArea: `iter` / `iterp` should safely handle "invalid" areas

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#17,065 opened on Mar 26, 2026

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@ Script APIRequest / Suggestiongood first issue

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Description

The following code

core.register_chatcommand("test_va", {
	func = function(name, param)
		local p1, p2 = vector.new(0,16,0), vector.new(15,31,15)
		local va = VoxelArea(p1, p2)
		local vmax = va:getVolume() -- this is 4096
		for i in va:iter(0, 16, 0, 15, 0, 15) do
			if i < 0 or i > vmax then
				return false, ("index %d is invalid"):format(i)
			end
		end
		return true
	end
})

currently fails as iter returns nonsense and eventually even out-of-range values.

The "mistake" by the caller is that y=0 is not even in the area. However I think it would be more useful if the API handled such usage safely and correctly.

Wanted behavior (with the values from the example code):

  • va:iter(0, 10, 0, 15, 20, 15) is equivalent to va:iter(0, 16, 0, 15, 20, 15)
  • va:iter(0, 10, 0, 15, 12, 15) produces no results

Contributor guide

Research direction
Find the implementations of VoxelArea::iter and VoxelArea::iterp in the Luanti C++ source code (likely in src/voxelarea.h or src/voxelalgorithms.cpp). Understand how they compute the flat index from coordinates. Modify them to clamp the coordinates to the valid range within the VoxelArea, so that invalid coordinates are safely handled.
Tech stack
lua
Domain
backend
Issue type
Bug
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
2
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.
Active
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
Clear
Prerequisites
C++Lua
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
75