CollisionResponseFunction called with sprite which has collisions disabled?

SDK Bug Reports
1

SDK version: 3.1.2

I am encountering a sporadic bug in my game where the collision response function of a sprite is called with another sprite that has collisions disabled.

Here is the situation:

LCDSprite *sprite_a = pd->sprite->newSprite();
LCDSprite *sprite_b = pd->sprite->newSprite();
pd->sprite->setCollisionsEnabled(sprite_a, true);
pd->sprite->setCollisionsResponseFunction(sprite_a, my_collision_response);
pd->sprite->setCollisionsEnabled(sprite_b, false);

And, under some circumstances (which are still unclear to me), this happens:

SpriteCollisionResponse my_collision_response(LCDSprite *sprite, LCDSprite *other)
{
   assert(pd->sprite->collisionsEnabled(sprite));
   // XXX: this next line sometimes asserts!
   assert(pd->sprite->collisionsEnabled(other));
}

The SDK docs for playdate->sprite->setCollisionsEnabled say:

Set the collisionsEnabled flag of the given sprite (along with the collideRect, this determines whether the sprite participates in collisions). One is true, 0 is false. Set to 1 by default.

So I would expect that both asserts never trip. Is this a bug in the SDK or am I misinterpreting the sprite API functionality?

2

Well, after a good deal of trial and error I think I figured out why this was happening: my collision response function was modifying the sprite list, which according to a footnote in the Lua doc must not be done.

After rearranging the code to defer the relevant logic outside the response function, it seems not to be happening anymore.