Issue #1318 open

Listing enum constants in error messages

created an issue

I think it would be helpful if errors caused by invalid enum constants listed the valid constants in the error message.

So instead of:


main.lua:2: Invalid draw mode: 0


[C]: in function 'rectangle'
main.lua:2: in function 'draw'
[C]: in function 'xpcall'

it would be something like:


main.lua:2: Invalid draw mode: 0

It can be: line or fill


[C]: in function 'rectangle'
main.lua:2: in function 'draw'
[C]: in function 'xpcall'

Most enums don't have that many constants:

Scancode: 194
KeyConstant: 144
CompressedImageFormat: 36
CanvasFormat: 17
GamepadButton: 15
Event: 14
CursorType: 13
JointType: 9
JoystickHat: 9
BlendMode: 8
DistanceModel: 7
StencilAction: 6
CompareMode: 6
GamepadAxis: 6
PowerState: 5
MeshDrawMode: 4
ShapeType: 4
AreaSpreadDistribution: 4
GraphicsLimit: 4
WrapMode: 4
FileMode: 4
BodyType: 3
CompressedDataFormat: 3
JoystickInputType: 3
ParticleInsertMode: 3
SpriteBatchUsage: 3
ArcType: 3
GraphicsFeature: 3
AlignMode: 3
BufferMode: 3
LineJoin: 3
MessageBoxType: 3
FilterMode: 2
PointStyle: 2
TimeUnit: 2
SourceType: 2
LineStyle: 2
FileDecoder: 2
ImageFormat: 2
FullscreenType: 2
StackType: 2
BlendAlphaMode: 2
DrawMode: 2

(Generated by this code, if anyone is interested.)

api = require('love_api') --

enums = {}

for _, module_ in ipairs(api.modules) do
  for _, enum in ipairs(module_.enums or {}) do
    table.insert(enums, {name =, constants = #enum.constants})

table.sort(enums, function(a, b) return a.constants > b.constants end)

for _, enum in ipairs(enums) do
  print(': '..enum.constants)

Obviously functions with key/scancode arguments are exempt! :)

But even CanvaFormat (which has a lot of constants) doesn't look so bad:


(If anyone is interested in the fake error code...)

function love.load(), 157/255, 220/255)
    p = [[

main.lua:2: Invalid canvas format: asdf

It can be: normal, hdr, rgba8, rgba4, rgba5a1, rgb565, rgb10a2, rgba16f, rgba32f, rg11b10f, srgb, r8, rg8, r16f, rg16f, r32f or rg32f


[C]: in function rectangle
main.lua:2: in function draw
[C]: in function xpcall

Press Ctrl+C or tap to copy this error

    screenshot = true

function love.draw()
    local pos = 70, pos, pos, - pos)
    if screenshot then'fakeerror_'..os.time()..'.png')
        screenshot = false

Comments (4)

  1. Raidho

    The error screen is there to provide debug information and it does, to all necessary extent. I don't think it should also duplicate the user manual.

  2. hahawoo reporter

    Actually what this issue (and #1317) should have been is: showing given and expected values in all messages for errors due to invalid arguments (unless it's a key/scancode argument or something else that makes it tricky).

  3. Bart van Strien
    • changed status to open

    I feel like this could be a worthwhile addition. That said, I'm afraid it's probably going to take a while, since it needs a proper solution, rather than us manually adding all these values to the error messages. It's not impossible, it just takes some dedication.

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