Make wielding automatically drop the item on your other hand (#27975)

* Make wielding automatically drop the item on your other hand

* Fix docs

* Remove redundant parameter

* Fix not deleting virtuals on fail

* Make count freeable hands method

* Add popup when dropping item

Content.Shared/Inventory/VirtualItem/SharedVirtualItemSystem.cs

@@ -4,6 +4,7 @@ using Content.Shared.Hands.EntitySystems;
 using Content.Shared.Interaction;
 using Content.Shared.Inventory.Events;
 using Content.Shared.Item;
+using Content.Shared.Popups;
 using Robust.Shared.Containers;
 using Robust.Shared.Network;
 using Robust.Shared.Prototypes;
@@ -29,6 +30,7 @@ public abstract class SharedVirtualItemSystem : EntitySystem
     [Dependency] private readonly SharedItemSystem _itemSystem = default!;
     [Dependency] private readonly InventorySystem _inventorySystem = default!;
     [Dependency] private readonly SharedHandsSystem _handsSystem = default!;
+    [Dependency] private readonly SharedPopupSystem _popup = default!;
 
     [ValidatePrototypeId<EntityPrototype>]
     private const string VirtualItem = "VirtualItem";
@@ -71,23 +73,53 @@ public abstract class SharedVirtualItemSystem : EntitySystem
     }
 
     #region Hands
+
     /// <summary>
     /// Spawns a virtual item in a empty hand
     /// </summary>
     /// <param name="blockingEnt">The entity we will make a virtual entity copy of</param>
     /// <param name="user">The entity that we want to insert the virtual entity</param>
-    public bool TrySpawnVirtualItemInHand(EntityUid blockingEnt, EntityUid user)
+    /// <param name="dropOthers">Whether or not to try and drop other items to make space</param>
+    public bool TrySpawnVirtualItemInHand(EntityUid blockingEnt, EntityUid user, bool dropOthers = false)
     {
-        return TrySpawnVirtualItemInHand(blockingEnt, user, out _);
+        return TrySpawnVirtualItemInHand(blockingEnt, user, out _, dropOthers);
     }
 
-    /// <inheritdoc cref="TrySpawnVirtualItemInHand(Robust.Shared.GameObjects.EntityUid,Robust.Shared.GameObjects.EntityUid)"/>
-    public bool TrySpawnVirtualItemInHand(EntityUid blockingEnt, EntityUid user, [NotNullWhen(true)] out EntityUid? virtualItem)
+    /// <inheritdoc cref="TrySpawnVirtualItemInHand(Robust.Shared.GameObjects.EntityUid,Robust.Shared.GameObjects.EntityUid,bool)"/>
+    public bool TrySpawnVirtualItemInHand(EntityUid blockingEnt, EntityUid user, [NotNullWhen(true)] out EntityUid? virtualItem, bool dropOthers = false)
     {
-        if (!TrySpawnVirtualItem(blockingEnt, user, out virtualItem) || !_handsSystem.TryGetEmptyHand(user, out var hand))
+        virtualItem = null;
+        if (!_handsSystem.TryGetEmptyHand(user, out var empty))
+        {
+            if (!dropOthers)
+                return false;
+
+            foreach (var hand in _handsSystem.EnumerateHands(user))
+            {
+                if (hand.HeldEntity is not { } held)
+                    continue;
+
+                if (held == blockingEnt || HasComp<VirtualItemComponent>(held))
+                    continue;
+
+                if (!_handsSystem.TryDrop(user, hand))
+                    continue;
+
+                if (!TerminatingOrDeleted(held))
+                    _popup.PopupClient(Loc.GetString("virtual-item-dropped-other", ("dropped", held)), user, user);
+
+                empty = hand;
+                break;
+            }
+        }
+
+        if (empty == null)
             return false;
 
-        _handsSystem.DoPickup(user, hand, virtualItem.Value);
+        if (!TrySpawnVirtualItem(blockingEnt, user, out virtualItem))
+            return false;
+
+        _handsSystem.DoPickup(user, empty, virtualItem.Value);
         return true;
     }
 
@@ -120,6 +152,7 @@ public abstract class SharedVirtualItemSystem : EntitySystem
     /// <param name="blockingEnt">The entity we will make a virtual entity copy of</param>
     /// <param name="user">The entity that we want to insert the virtual entity</param>
     /// <param name="slot">The slot to which we will insert the virtual entity (could be the "shoes" slot, for example)</param>
+    /// <param name="force">Whether or not to force an equip</param>
     public bool TrySpawnVirtualItemInInventory(EntityUid blockingEnt, EntityUid user, string slot, bool force = false)
     {
         return TrySpawnVirtualItemInInventory(blockingEnt, user, slot, force, out _);
@@ -140,6 +173,8 @@ public abstract class SharedVirtualItemSystem : EntitySystem
     /// that's done check if the found virtual entity is a copy of our matching entity,
     /// if it is, delete it
     /// </summary>
+    /// <param name="user">The entity that we want to delete the virtual entity from</param>
+    /// <param name="matching">The entity that made the virtual entity</param>
     /// <param name="slotName">Set this param if you have the name of the slot, it avoids unnecessary queries</param>
     public void DeleteInSlotMatching(EntityUid user, EntityUid matching, string? slotName = null)
     {
@@ -178,6 +213,7 @@ public abstract class SharedVirtualItemSystem : EntitySystem
     /// </summary>
     /// <param name="blockingEnt">The entity we will make a virtual entity copy of</param>
     /// <param name="user">The entity that we want to insert the virtual entity</param>
+    /// <param name="virtualItem">The virtual item, if spawned</param>
     public bool TrySpawnVirtualItem(EntityUid blockingEnt, EntityUid user, [NotNullWhen(true)] out EntityUid? virtualItem)
     {
         if (_netManager.IsClient)