[0.14.22] Items on belts do not move when activating belt

[Gangsir]

I actually experienced this bug while making a mod, but it can be replicated in vanilla factorio.

What I did:
I placed a line of transport belts, and somewhere in the middle of the line I disabled one of the belts. When I put items at the beginning of the line of belts, they moved across the belt until they hit the inactive belt, and stopped as expected. When I enabled the belt again, however, the items did not continue moving.

What I expected:

I expected that once I enabled the belt, the items would start moving across the now active belt. But, even though the belt under them was moving/moving the player, the items stayed still. They would eventually start moving if some new items entered the belt that they were on, I guess that triggers an update.

Steps to replicate:

1. Place a line of transport belts, about 7 long or so.
2. Hover your mouse over a transport belt near the middle of the line, then run the command below:

Code: Select all

/c game.player.selected.active = false

3. The belt will disable. Then, place some items at the start of the line of belts so they flow along until they stop at the inactive belt.
4. Reactivate the belt that you disabled, with the opposite of the above command.
5. Observe the bug as the items do not begin moving.

A gif of the bug being replicated:

https://my.mixtape.moe/lbnwwe.webm

[Rseding91]

That's due to the nature of how belts work: the belt you activated had no work to do and the belt before it won't activate unless the belt in front asks it to.

I don't consider this worth fixing. If anything I would make it so you can't disable belts through active=true/false. In 0.15 several entities will no longer work with that property as it does a lot of things like this that break the normal game logic and would require a large amount of "hacks" to prevent.