Using a consumable item with a Negative Consumption value fails if the consumed resource is zero.

[FrankIsAtank]

FoundryVTT V 11 Stable 306
DnD5e 2.3.1

To reproduce :

1. Create a player character actor.
2. Add a Consumable item to the actor.
3. Give the new item these properties :

• Activation Cost : Action
• Resource Consumption -1 'resources.primary.value' Attribute

4. Return to the character sheet and try to consume the new item.

Observed behaviour :
The item fails to be consumed, presumably because it checks that the consumed resource is available.
A warning notification appears with "New Consumable has run out of its designated Attribute!".

Expected behaviour :
With a negative cost, the intent is for consuming the item to increase an attribute, such as adding to a resource counter. Doing so when that attribute is zero should not fail.

[Hoppyhob]

I wasn't able to recreate this with:
FoundryVTT V 11 Stable 308
DnD5e 2.3.1 or the 2.4.x branch

It appears from the code we warn with this message(ConsumeWarningNoQuantity) here (in item.mjs):

let remaining = quantity - amount;
    if ( remaining < 0 ) {
      ui.notifications.warn(game.i18n.format("DND5E.ConsumeWarningNoQuantity", {name: this.name, type: typeLabel}));
      return false;
    }

Which with a quantity of zero (gotten from resources.primary.value or defaulted to 0 if null) would be working as expected 0 - -1 = 1 which is greater than zero. (This should only warn if the resource value is -2 or lower)

[krbz999]

Which with a quantity of zero (gotten from resources.primary.value or defaulted to 0 if null) would be working as expected 0 - -1 = 1 which is greater than zero. (This should only warn if the resource value is -2 or lower)

I suspect it is related to #2165.

resource = foundry.utils.getProperty(this.actor.system, consume.target) becomes undefined, and then fails here:

    // Verify that a consumed resource is available
    if ( resource === undefined ) {
      ui.notifications.warn(game.i18n.format("DND5E.ConsumeWarningNoSource", {name: this.name, type: typeLabel}));
      return false;
    }

[krbz999]

OK, maybe it's not so weird that these (value and max) get deleted given that we delete them.

https://github.com/foundryvtt/dnd5e/blob/master/module/applications/actor/character-sheet.mjs#L30