consumed_items: how does it work?

[i142857]

The 2.0 changelog says:

Changed on_built_entity event. Instead of stack/item, it passes consumed_items - modifiable stack of items used for the building.

Sounds great but I can't figure out how I'm supposed to use that. I am trying to "refund" the item used when placing the entity. Ideally the item would return to the cursor_stack and the player could place it again.

But nothing I tried works:

Code: Select all

local function on_built_entity(event)
    for i = 1, #event.consumed_items do
        local stack = event.consumed_items[i]
        game.print("Stack " .. tostring(i) .. " is " .. serpent.line(stack))
        if stack.valid_for_read and stack.prototype.group.name == "test" then
            game.print("Refunding")
            -- NONE OF THESE WORK:
            -- stack.count = 0
            -- stack.clear()
            -- event.consumed_items.remove(stack)
            -- event.consumed_items.remove({ name = stack.name, count = 1 })

In every case, it's as if I hadn't done anything. And if I try to do it manually, say by just adding the item back to player.cursor_stack, that doesn't work either because during on_built_entity, player.cursor_stack.valid_for_read is false.

So I honestly can't figure out how I'm supposed to use this. If what I'm trying to achieve is not supported using consumed_items, then maybe document what kind of changes are supported.

[curiosity]

Are you sure the item is not refunded? Or is it merely not in hand? valid_for_read == false means the stack is empty.

Edit: oh, it's a separate inventory. I'd guess it has put in there the items that it took. All your attempts make absolutely no sense in this context.

[i142857]

But the description says this modifiable. If it says "I consumed a Foo" and I modify it to "no, actually you consumed nothing", then it should have some effect, no? Perhaps I was overly optimistic about it returning the item, but there is no documentation on what this modifiable inventory does when modified.

I am starting to guess that this only affects stats and nothing else, but even in that case it would be worth documenting.

[curiosity]

You can modify it, so the changelog is technically correct. But then the changelog was never definitive regarding documentation, the docs themselves are. And there is no remark for that field in the docs, it's just an inventory. And pretty sure an immutable LuaInventory in impossible anyway.

[Therenas]

There is quite a lot of confusion here, so let me try to clear it up.

The inventory you get from the event is just for convenient handling of the consumed items. It's ephemeral, meaning it'll only be valid during the event. Manipulating that inventory will not change anything about the player, since it's not the player's inventory, it's just a temporary one off to the side.

If you want to refund the item, you need to change the player's inventory or cursor. You can do this like so, for example:

Code: Select all

script.on_event(defines.events.on_built_entity, function(event)
    local player = game.players[event.player_index]
    player.cursor_stack.set_stack(event.consumed_items[1])
end)

Also, note that valid_for_read is only related to reading what the player has in their cursor. It being false means the player's cursor is empty, not that you can't set it to something else.

I expanded the docs for the event to be clearer about what the inventory is for the next release, thanks for the report.