Add GrantCondition trait.

OpenRA.Mods.Common/OpenRA.Mods.Common.csproj

@@ -774,6 +774,7 @@
     <Compile Include="Traits\AutoCarryable.cs" />
     <Compile Include="Traits\AutoCarryall.cs" />
     <Compile Include="Traits\World\CliffBackImpassabilityLayer.cs" />
+    <Compile Include="Traits\Upgrades\GrantCondition.cs" />
   </ItemGroup>
   <Import Project="$(MSBuildToolsPath)\Microsoft.CSharp.targets" />
   <Target Name="AfterBuild">

OpenRA.Mods.Common/Traits/Upgrades/GrantCondition.cs

@@ -0,0 +1,56 @@
+#region Copyright & License Information
+/*
+ * Copyright 2007-2016 The OpenRA Developers (see AUTHORS)
+ * This file is part of OpenRA, which is free software. It is made
+ * available to you 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. For more
+ * information, see COPYING.
+ */
+#endregion
+
+using OpenRA.Traits;
+
+namespace OpenRA.Mods.Common.Traits
+{
+	[Desc("Grants a condition while the trait is active.")]
+	class GrantConditionInfo : UpgradableTraitInfo
+	{
+		[FieldLoader.Require]
+		[UpgradeGrantedReference]
+		[Desc("Condition to grant.")]
+		public readonly string Condition = null;
+
+		public override object Create(ActorInitializer init) { return new GrantCondition(this); }
+	}
+
+	class GrantCondition : UpgradableTrait<GrantConditionInfo>
+	{
+		UpgradeManager manager;
+		int conditionToken = UpgradeManager.InvalidConditionToken;
+
+		public GrantCondition(GrantConditionInfo info)
+			: base(info) { }
+
+		protected override void Created(Actor self)
+		{
+			manager = self.Trait<UpgradeManager>();
+
+			base.Created(self);
+		}
+
+		protected override void TraitEnabled(Actor self)
+		{
+			if (conditionToken == UpgradeManager.InvalidConditionToken)
+				conditionToken = manager.GrantCondition(self, Info.Condition);
+		}
+
+		protected override void TraitDisabled(Actor self)
+		{
+			if (conditionToken == UpgradeManager.InvalidConditionToken)
+				return;
+
+			conditionToken = manager.RevokeCondition(self, conditionToken);
+		}
+	}
+}