container: add C_Container.HasContainerItem

Classic Era addition (present in the 1.15.x client, absent in 5.4.8) — a
plain occupancy check for a bag slot. Occupancy sibling of
GetContainerItemID: resolves (bagIndex, slotIndex) the same way and returns
whether the CGItem is non-null. Presence only, so it reports true for a
just-looted item even before its static data caches. Returns false for
empty slots and out-of-range indices.

Author: brues-code

README.md

@@ -24,7 +24,7 @@ Full per-function reference: **[docs/API.md](docs/API.md)**.
 | [Combat](docs/API.md#combat) | `InCombatLockdown` |
 | [CVar](docs/API.md#cvar) | `C_CVar.GetCVarBool` |
 | [Cursor](docs/API.md#cursor) | `GetCursorInfo` |
-| [Container](docs/API.md#container) | `C_Container.CalculateTotalNumberOfFreeBagSlots`, `C_Container.GetContainerItemCharges`, `C_Container.GetContainerItemDurability`, `C_Container.GetContainerItemID`, `C_Container.GetContainerItemRepairCost`, `C_Container.GetContainerNumFreeSlots`, `C_Container.GetItemCooldown`, `C_Container.IsContainerItemOpenable`, `C_Container.MoveItem`, `C_Container.PlayerHasHearthstone`, `C_Container.SwapItems`, `C_Container.UseHearthstone`, `GetItemCooldown` |
+| [Container](docs/API.md#container) | `C_Container.CalculateTotalNumberOfFreeBagSlots`, `C_Container.GetContainerItemCharges`, `C_Container.GetContainerItemDurability`, `C_Container.GetContainerItemID`, `C_Container.GetContainerItemRepairCost`, `C_Container.GetContainerNumFreeSlots`, `C_Container.GetItemCooldown`, `C_Container.HasContainerItem`, `C_Container.IsContainerItemOpenable`, `C_Container.MoveItem`, `C_Container.PlayerHasHearthstone`, `C_Container.SwapItems`, `C_Container.UseHearthstone`, `GetItemCooldown` |
 | [Coroutine](docs/API.md#coroutine) | `coroutine.create`, `coroutine.resume`, `coroutine.yield`, `coroutine.status`, `coroutine.wrap` |
 | [Creature](docs/API.md#creature) | `C_CreatureInfo.GetCreatureID`, `C_CreatureInfo.GetCreatureInfoByID`, `C_CreatureInfo.RequestLoadCreatureByID`, `C_CreatureInfo.GetRaceInfo`, `C_CreatureInfo.GetClassInfo`, `C_CreatureInfo.GetCreatureFamilyInfo`, `C_CreatureInfo.GetCreatureFamilyIDs`, `C_CreatureInfo.GetFactionInfo`, `C_CreatureInfo.GetCreatureTypeInfo`, `C_CreatureInfo.GetCreatureTypeIDs` |
 | EncodingUtil | `C_EncodingUtil.CompressString`, `C_EncodingUtil.DecompressString`, `C_EncodingUtil.EncodeBase64`, `C_EncodingUtil.DecodeBase64`, `C_EncodingUtil.EncodeHex`, `C_EncodingUtil.DecodeHex`, `C_EncodingUtil.SerializeJSON`, `C_EncodingUtil.DeserializeJSON`, `C_EncodingUtil.SerializeCBOR`, `C_EncodingUtil.DeserializeCBOR` |

docs/API.md

@@ -40,6 +40,7 @@ build instructions.
 
 - [Container](#container)
   - [`C_Container.GetContainerItemID(bagIndex, slotIndex)`](#c_containergetcontaineritemidbagindex-slotindex)
+  - [`C_Container.HasContainerItem(bagIndex, slotIndex)`](#c_containerhascontaineritembagindex-slotindex)
   - [`GetItemCooldown(itemInfo)` / `C_Container.GetItemCooldown(itemID)`](#getitemcooldowniteminfo--c_containergetitemcooldownitemid)
   - [`C_Container.GetContainerItemDurability(containerIndex, slotIndex)`](#c_containergetcontaineritemdurabilitycontainerindex-slotindex)
   - [`C_Container.GetContainerItemRepairCost(containerIndex, slotIndex)`](#c_containergetcontaineritemrepaircostcontainerindex-slotindex)
@@ -1061,6 +1062,25 @@ for slot = 1, 16 do
 end
 ```
 
+### `C_Container.HasContainerItem(bagIndex, slotIndex)`
+
+Returns `true` if the given bag slot currently holds an item, `false`
+otherwise (empty slot or out-of-range indices). The occupancy sibling of
+`GetContainerItemID` — same slot resolution, but a plain presence check.
+
+- `bagIndex = 0` — the player's main backpack; `1..4` — equipped bag slots.
+- `slotIndex` — 1-based.
+
+Presence only: it does **not** require the item's static data to be cached,
+so it returns `true` for a just-looted item even before `GetContainerItemID`
+/ `GetItemInfo` resolve for it.
+
+```lua
+if C_Container.HasContainerItem(0, 1) then
+    -- backpack slot 1 is occupied
+end
+```
+
 ### `GetItemCooldown(itemInfo)` / `C_Container.GetItemCooldown(itemID)`
 
 Returns `(startTime, duration, enable)` for the cooldown of the

src/container/HasItem.cpp

@@ -0,0 +1,52 @@
+// This file is part of ClassicAPI.
+//
+// ClassicAPI is free software: you can redistribute it and/or modify it under the terms
+// of the GNU General Public License as published by the Free Software Foundation, either
+// version 3 of the License, or (at your option) any later version.
+//
+// ClassicAPI is distributed in the hope that it will be useful, but WITHOUT ANY
+// WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR
+// PURPOSE. See the GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License along with
+// ClassicAPI. If not, see <https://www.gnu.org/licenses/>.
+
+// `C_Container.HasContainerItem(bagIndex, slotIndex)` — returns whether the
+// given bag slot currently holds an item (a Classic Era addition). It's the
+// occupancy sibling of `GetContainerItemID`: resolves the slot to its CGItem
+// the same way (`Item::Location::ResolveBag` → engine `PackBagSlot` →
+// `GetItemBySlot`), and a populated slot yields a non-null pointer while an
+// empty slot yields null. Presence only — it does not depend on the item's
+// static data being cached. Returns `false` for empty slots and invalid
+// bag/slot indices.
+
+#include "Game.h"
+#include "item/Location.h"
+
+namespace Container::HasItem {
+
+namespace {
+
+int __fastcall Script_C_Container_HasContainerItem(void *L) {
+    if (!Game::Lua::IsNumber(L, 1) || !Game::Lua::IsNumber(L, 2)) {
+        Game::Lua::Error(L, "Usage: C_Container.HasContainerItem(bagIndex, slotIndex)");
+        return 0;
+    }
+    const int bagID = static_cast<int>(Game::Lua::ToNumber(L, 1));
+    const int slotIndex = static_cast<int>(Game::Lua::ToNumber(L, 2));
+
+    const bool hasItem = Item::Location::ResolveBag(L, bagID, slotIndex) != nullptr;
+    Game::Lua::PushBool(L, hasItem);
+    return 1;
+}
+
+void RegisterLuaFunctions() {
+    Game::Lua::RegisterTableFunction("C_Container", "HasContainerItem",
+                                     &Script_C_Container_HasContainerItem);
+}
+
+const Game::ModuleAutoRegister _autoreg{&RegisterLuaFunctions};
+
+} // namespace
+
+} // namespace Container::HasItem