1 files changed, 123 insertions, 0 deletions
diff --git a/src/SMAPI/Framework/ModLoading/Rewriters/Harmony1AssemblyRewriter.cs b/src/SMAPI/Framework/ModLoading/Rewriters/Harmony1AssemblyRewriter.cs
new file mode 100644
index 00000000..be98a666
--- /dev/null
+++ b/src/SMAPI/Framework/ModLoading/Rewriters/Harmony1AssemblyRewriter.cs
@@ -0,0 +1,123 @@
+using System;
+using HarmonyLib;
+using Mono.Cecil;
+using Mono.Cecil.Cil;
+using StardewModdingAPI.Framework.ModLoading.Framework;
+using StardewModdingAPI.Framework.ModLoading.RewriteFacades;
+
+namespace StardewModdingAPI.Framework.ModLoading.Rewriters
+{
+    /// <summary>Rewrites Harmony 1.x assembly references to work with Harmony 2.x.</summary>
+    internal class Harmony1AssemblyRewriter : BaseInstructionHandler
+    {
+        /*********
+        ** Fields
+        *********/
+        /// <summary>Whether any Harmony 1.x types were replaced.</summary>
+        private bool ReplacedTypes;
+
+
+        /*********
+        ** Public methods
+        *********/
+        /// <summary>Construct an instance.</summary>
+        public Harmony1AssemblyRewriter()
+            : base(defaultPhrase: "Harmony 1.x") { }
+
+        /// <summary>Rewrite a type reference if needed.</summary>
+        /// <param name="module">The assembly module containing the instruction.</param>
+        /// <param name="type">The type definition to handle.</param>
+        /// <param name="replaceWith">Replaces the type reference with a new one.</param>
+        /// <returns>Returns whether the type was changed.</returns>
+        public override bool Handle(ModuleDefinition module, TypeReference type, Action<TypeReference> replaceWith)
+        {
+            // rewrite Harmony 1.x type to Harmony 2.0 type
+            if (type.Scope is AssemblyNameReference scope && scope.Name == "0Harmony" && scope.Version.Major == 1)
+            {
+                Type targetType = this.GetMappedType(type);
+                replaceWith(module.ImportReference(targetType));
+                this.MarkRewritten();
+                this.ReplacedTypes = true;
+                return true;
+            }
+
+            return false;
+        }
+
+        /// <summary>Rewrite a CIL instruction reference if needed.</summary>
+        /// <param name="module">The assembly module containing the instruction.</param>
+        /// <param name="cil">The CIL processor.</param>
+        /// <param name="instruction">The CIL instruction to handle.</param>
+        /// <param name="replaceWith">Replaces the CIL instruction with a new one.</param>
+        /// <returns>Returns whether the instruction was changed.</returns>
+        public override bool Handle(ModuleDefinition module, ILProcessor cil, Instruction instruction, Action<Instruction> replaceWith)
+        {
+            // rewrite Harmony 1.x methods to Harmony 2.0
+            MethodReference methodRef = RewriteHelper.AsMethodReference(instruction);
+            if (this.TryRewriteMethodsToFacade(module, methodRef))
+                return true;
+
+            // rewrite renamed fields
+            FieldReference fieldRef = RewriteHelper.AsFieldReference(instruction);
+            if (fieldRef != null)
+            {
+                if (fieldRef.DeclaringType.FullName == "HarmonyLib.HarmonyMethod" && fieldRef.Name == "prioritiy")
+                    fieldRef.Name = nameof(HarmonyMethod.priority);
+            }
+
+            return false;
+        }
+
+
+        /*********
+        ** Private methods
+        *********/
+        /// <summary>Rewrite methods to use Harmony facades if needed.</summary>
+        /// <param name="module">The assembly module containing the method reference.</param>
+        /// <param name="methodRef">The method reference to map.</param>
+        private bool TryRewriteMethodsToFacade(ModuleDefinition module, MethodReference methodRef)
+        {
+            if (!this.ReplacedTypes)
+                return false; // not Harmony (or already using Harmony 2.0)
+
+            // get facade type
+            Type toType;
+            switch (methodRef?.DeclaringType.FullName)
+            {
+                case "HarmonyLib.Harmony":
+                    toType = typeof(HarmonyInstanceMethods);
+                    break;
+
+                case "HarmonyLib.AccessTools":
+                    toType = typeof(AccessToolsMethods);
+                    break;
+
+                default:
+                    return false;
+            }
+
+            // map if there's a matching method
+            if (RewriteHelper.HasMatchingSignature(toType, methodRef))
+            {
+                methodRef.DeclaringType = module.ImportReference(toType);
+                return true;
+            }
+
+            return false;
+        }
+
+        /// <summary>Get an equivalent Harmony 2.x type.</summary>
+        /// <param name="type">The Harmony 1.x method.</param>
+        private Type GetMappedType(TypeReference type)
+        {
+            // main Harmony object
+            if (type.FullName == "Harmony.HarmonyInstance")
+                return typeof(Harmony);
+
+            // other objects
+            string fullName = type.FullName.Replace("Harmony.", "HarmonyLib.");
+            string targetName = typeof(Harmony).AssemblyQualifiedName.Replace(typeof(Harmony).FullName, fullName);
+            return Type.GetType(targetName, throwOnError: true);
+        }
+    }
+}