egametang/ET · error

invalid slot index: {slotIndex}

Error message

invalid slot index: {slotIndex}

What it means

Thrown by the SERVER-side ItemComponentSystem.EnsureSlotIndex when slotIndex < 0. EnsureSlotIndex is the guard inside server SetSlotItem (line 175) and is the first of two checks (negative, then over-capacity). A negative index is always a programming error since valid slots are 0..Capacity-1.

Source

Thrown at Packages/cn.etetet.item/Scripts/Hotfix/Server/ItemComponentSystem.cs:200

        /// <summary>
        /// 尝试获取指定槽位的物品
        /// </summary>
        public static Item TryGetSlotItem(this ItemComponent self, int slotIndex)
        {
            if ((uint)slotIndex < (uint)self.SlotItems.Count)
            {
                return self.SlotItems[slotIndex];
            }

            return null;
        }

        private static void EnsureSlotIndex(ItemComponent self, int slotIndex)
        {
            if (slotIndex < 0)
            {
                throw new Exception($"invalid slot index: {slotIndex}");
            }

            if (slotIndex >= self.Capacity)
            {
                throw new Exception($"slot index {slotIndex} exceeds capacity {self.Capacity}");
            }
        }

        private static void EnsureSlotContainerSize(ItemComponent self, int size)
        {
            if (size <= 0)
            {
                return;
            }

            if (self.SlotItems.Count >= size)
            {
                return;

View on GitHub (pinned to 5cab01f7a8)

Solutions

1. Always check FindEmptySlot() >= 0 before using the result (see ItemHelper.AddItem line 78 for the correct pattern).
2. If storing a sentinel for 'no slot', use a nullable int or a separate flag, never -1 in a field that flows into SetSlotItem.
3. Audit server code that constructs slotIndex from arithmetic and clamp at >= 0.

Example fix

// before
int slot = component.FindEmptySlot();
component.SetSlotItem(slot, item); // slot may be -1

// after
int slot = component.FindEmptySlot();
if (slot < 0) { /* handle full bag */ return; }
component.SetSlotItem(slot, item);

int slot = component.FindEmptySlot();
if (slot < 0) { /* bag full or no slot */ return; }
component.SetSlotItem(slot, item);

When it happens

Trigger: A server caller passes a negative slotIndex to SetSlotItem (e.g. the result of FindEmptySlot == -1 used without checking). FindEmptySlot returns -1 to mean 'no slot', so feeding that straight into SetSlotItem triggers this exact throw.

Common situations: Using FindEmptySlot()'s return value without testing for -1; an off-by-one in a loop that decrements past zero; a deserialized SlotIndex that was never initialized (default 0 is fine, but -1 used as an 'empty' marker persists into storage).

Related errors

• slot index {slotIndex} exceeds capacity {self.Capacity}
• invalid capacity: {capacity}
• invalid item count
• slot index {slotIndex} exceeds capacity {self.Capacity}
• item config not found: {configId}

AI-assisted analysis of egametang/ET@5cab01f7a8 (2026-08-13). Data as JSON: /api/errors/d414c57a44320201. Report an issue: GitHub.