disallow stacking polymorphs by default (#9845)

Co-authored-by: Kara <lunarautomaton6@gmail.com>

Content.Server/Polymorph/Systems/PolymorphableSystem.cs

@@ -1,5 +1,4 @@
 using Content.Server.Actions;
-using Content.Server.Body.Components;
 using Content.Server.Buckle.Components;
 using Content.Server.Inventory;
 using Content.Server.Mind.Commands;
@@ -13,11 +12,8 @@ using Content.Shared.Damage;
 using Content.Shared.Hands.EntitySystems;
 using Content.Shared.Polymorph;
 using Robust.Server.Containers;
-using Robust.Shared.Audio;
 using Robust.Shared.Containers;
 using Robust.Shared.Map;
-using Robust.Shared.Physics.Dynamics;
-using Robust.Shared.Player;
 using Robust.Shared.Prototypes;
 using Robust.Shared.Utility;
 
@@ -90,6 +86,10 @@ namespace Content.Server.Polymorph.Systems
             /// logic and conditions specified in the prototype, and everything else that may be needed.
             /// I am clinically insane - emo
 
+            // if it's already morphed, don't allow it again with this condition active.
+            if (!proto.AllowRepeatedMorphs && HasComp<PolymorphedEntityComponent>(target))
+                return null;
+
             // mostly just for vehicles
             if (TryComp<BuckleComponent>(target, out var buckle))
                 buckle.TryUnbuckle(target, true);

Content.Shared/Polymorph/PolymorphPrototype.cs

@@ -88,6 +88,9 @@ namespace Content.Shared.Polymorph
         /// </summary>
         [DataField("revertOnDeath", serverOnly: true)]
         public bool RevertOnDeath = true;
+
+        [DataField("allowRepeatedMorphs", serverOnly: true)]
+        public bool AllowRepeatedMorphs = false;
     }
 
     public enum PolymorphInventoryChange : byte

Resources/Prototypes/Polymorphs/admin.yml

@@ -5,33 +5,39 @@
   transferName: true
   transferHumanoidAppearance: true
   inventory: Transfer
+  allowRepeatedMorphs: true
 
 - type: polymorph
   id: AdminMonkeySmite
   entity: MobMonkey
   forced: true
   inventory: Drop
+  allowRepeatedMorphs: true
 
 - type: polymorph
   id: AdminBreadSmite
   entity: FoodBreadPlain
   forced: true
   inventory: Drop
+  allowRepeatedMorphs: true
 
 - type: polymorph
   id: AdminInstrumentSmite
   entity: SuperSynthesizerInstrument
   forced: true
   inventory: Drop
+  allowRepeatedMorphs: true
 
 - type: polymorph
   id: AdminMouseSmite
   entity: MobMouse
   forced: true
   inventory: Drop
+  allowRepeatedMorphs: true
 
 - type: polymorph
   id: AdminDisposalsSmite
   entity: DisposalUnit
   forced: true
   inventory: Drop
+  allowRepeatedMorphs: true