Make canisters dump their contents on destruction. (#5177)

* Make canisters dump their contents on destruction.

* Address reviews

Content.Server/Atmos/Piping/Unary/EntitySystems/GasCanisterSystem.cs

@@ -3,6 +3,7 @@ using Content.Server.Atmos.Components;
 using Content.Server.Atmos.EntitySystems;
 using Content.Server.Atmos.Piping.Components;
 using Content.Server.Atmos.Piping.Unary.Components;
+using Content.Server.Destructible;
 using Content.Server.Hands.Components;
 using Content.Server.NodeContainer;
 using Content.Server.NodeContainer.NodeGroups;
@@ -44,6 +45,22 @@ namespace Content.Server.Atmos.Piping.Unary.EntitySystems
             SubscribeLocalEvent<GasCanisterComponent, GasCanisterHoldingTankEjectMessage>(OnHoldingTankEjectMessage);
             SubscribeLocalEvent<GasCanisterComponent, GasCanisterChangeReleasePressureMessage>(OnCanisterChangeReleasePressure);
             SubscribeLocalEvent<GasCanisterComponent, GasCanisterChangeReleaseValveMessage>(OnCanisterChangeReleaseValve);
+
+        }
+
+        /// <summary>
+        /// Completely dumps the content of the canister into the world.
+        /// </summary>
+        public void PurgeContents(EntityUid uid, GasCanisterComponent? canister = null, ITransformComponent? transform = null)
+        {
+            if (!Resolve(uid, ref canister, ref transform)) return;
+
+            var environment = _atmosphereSystem.GetTileMixture(transform.Coordinates, true);
+
+            if (environment is not null)
+                _atmosphereSystem.Merge(environment, canister.Air);
+
+            canister.Air.Clear();
         }
 
         private void OnCanisterStartup(EntityUid uid, GasCanisterComponent canister, ComponentStartup args)

Content.Server/Destructible/Thresholds/Behaviors/DumpCanisterBehavior.cs

@@ -0,0 +1,20 @@
+using System;
+using Content.Server.Atmos.Piping.Unary.Components;
+using Content.Server.Atmos.Piping.Unary.EntitySystems;
+using Robust.Shared.GameObjects;
+using Robust.Shared.Serialization.Manager.Attributes;
+
+namespace Content.Server.Destructible.Thresholds.Behaviors
+{
+    [Serializable]
+    [DataDefinition]
+    public class DumpCanisterBehavior: IThresholdBehavior
+    {
+        public void Execute(IEntity owner, DestructibleSystem system)
+        {
+            var gasCanisterSystem = EntitySystem.Get<GasCanisterSystem>();
+
+            gasCanisterSystem.PurgeContents(owner.Uid);
+        }
+    }
+}

Resources/Prototypes/Entities/Structures/Storage/Canisters/gas_canisters.yml

@@ -267,6 +267,7 @@
               max: 1
         - !type:DoActsBehavior
           acts: [ "Destruction" ]
+        - !type:DumpCanisterBehavior
 
 - type: entity
   parent: GasCanister