Add mob retaliation (#19901)

Content.Server/NPC/Systems/NpcFactionSystem.cs

@@ -1,15 +1,15 @@
 using Content.Server.NPC.Components;
 using Robust.Shared.Prototypes;
 using System.Linq;
+using JetBrains.Annotations;
 
 namespace Content.Server.NPC.Systems;
 
 /// <summary>
 ///     Outlines faction relationships with each other.
 /// </summary>
-public sealed class NpcFactionSystem : EntitySystem
+public sealed partial class NpcFactionSystem : EntitySystem
 {
-    [Dependency] private readonly FactionExceptionSystem _factionException = default!;
     [Dependency] private readonly EntityLookupSystem _lookup = default!;
     [Dependency] private readonly IPrototypeManager _protoManager = default!;
 
@@ -26,6 +26,8 @@ public sealed class NpcFactionSystem : EntitySystem
         _sawmill = Logger.GetSawmill("faction");
         SubscribeLocalEvent<NpcFactionMemberComponent, ComponentStartup>(OnFactionStartup);
         _protoManager.PrototypesReloaded += OnProtoReload;
+
+        InitializeException();
         RefreshFactions();
     }
 
@@ -134,12 +136,15 @@ public sealed class NpcFactionSystem : EntitySystem
         if (TryComp<FactionExceptionComponent>(entity, out var factionException))
         {
             // ignore anything from enemy faction that we are explicitly friendly towards
-            return hostiles.Where(target => !_factionException.IsIgnored(factionException, target));
+            return hostiles
+                .Union(GetHostiles(entity, factionException))
+                .Where(target => !IsIgnored(entity, target, factionException));
         }
 
         return hostiles;
     }
 
+    [PublicAPI]
     public IEnumerable<EntityUid> GetNearbyFriendlies(EntityUid entity, float range, NpcFactionMemberComponent? component = null)
     {
         if (!Resolve(entity, ref component, false))