remove base.Entry() method calls (#362)

src/StardewModdingAPI/Framework/ModLoading/Rewriters/VirtualEntryCallRemover.cs

@@ -0,0 +1,90 @@
+using System;
+using Mono.Cecil;
+using Mono.Cecil.Cil;
+
+namespace StardewModdingAPI.Framework.ModLoading.Rewriters
+{
+    /// <summary>Rewrites virtual calls to the <see cref="Mod.Entry"/> method.</summary>
+    internal class VirtualEntryCallRemover : IInstructionHandler
+    {
+        /*********
+        ** Properties
+        *********/
+        /// <summary>The type containing the method.</summary>
+        private readonly Type ToType;
+
+        /// <summary>The name of the method.</summary>
+        private readonly string MethodName;
+
+
+        /*********
+        ** Accessors
+        *********/
+        /// <summary>A brief noun phrase indicating what the instruction finder matches.</summary>
+        public string NounPhrase { get; }
+
+
+        /*********
+        ** Public methods
+        *********/
+        /// <summary>Construct an instance.</summary>
+        public VirtualEntryCallRemover()
+        {
+            this.ToType = typeof(Mod);
+            this.MethodName = nameof(Mod.Entry);
+            this.NounPhrase = $"{this.ToType.Name}::{this.MethodName}";
+        }
+
+        /// <summary>Perform the predefined logic for a method if applicable.</summary>
+        /// <param name="module">The assembly module containing the instruction.</param>
+        /// <param name="method">The method definition containing the instruction.</param>
+        /// <param name="assemblyMap">Metadata for mapping assemblies to the current platform.</param>
+        /// <param name="platformChanged">Whether the mod was compiled on a different platform.</param>
+        public InstructionHandleResult Handle(ModuleDefinition module, MethodDefinition method, PlatformAssemblyMap assemblyMap, bool platformChanged)
+        {
+            return InstructionHandleResult.None;
+        }
+
+        /// <summary>Perform the predefined logic for an instruction if applicable.</summary>
+        /// <param name="module">The assembly module containing the instruction.</param>
+        /// <param name="cil">The CIL processor.</param>
+        /// <param name="instruction">The instruction to handle.</param>
+        /// <param name="assemblyMap">Metadata for mapping assemblies to the current platform.</param>
+        /// <param name="platformChanged">Whether the mod was compiled on a different platform.</param>
+        public InstructionHandleResult Handle(ModuleDefinition module, ILProcessor cil, Instruction instruction, PlatformAssemblyMap assemblyMap, bool platformChanged)
+        {
+            if (!this.IsMatch(instruction))
+                return InstructionHandleResult.None;
+
+            // get instructions comprising method call
+            int index = cil.Body.Instructions.IndexOf(instruction);
+            Instruction loadArg0 = cil.Body.Instructions[index - 2];
+            Instruction loadArg1 = cil.Body.Instructions[index - 1];
+            if (loadArg0.OpCode != OpCodes.Ldarg_0)
+                throw new InvalidOperationException($"Unexpected instruction sequence while removing virtual {this.ToType.Name}.{this.MethodName} call: found {loadArg0.OpCode.Name} instead of {OpCodes.Ldarg_0.Name}");
+            if (loadArg1.OpCode != OpCodes.Ldarg_1)
+                throw new InvalidOperationException($"Unexpected instruction sequence while removing virtual {this.ToType.Name}.{this.MethodName} call: found {loadArg1.OpCode.Name} instead of {OpCodes.Ldarg_1.Name}");
+
+            // remove method call
+            cil.Remove(loadArg0);
+            cil.Remove(loadArg1);
+            cil.Remove(instruction);
+            return InstructionHandleResult.Rewritten;
+        }
+
+
+        /*********
+        ** Protected methods
+        *********/
+        /// <summary>Get whether a CIL instruction matches.</summary>
+        /// <param name="instruction">The IL instruction.</param>
+        protected bool IsMatch(Instruction instruction)
+        {
+            MethodReference methodRef = RewriteHelper.AsMethodReference(instruction);
+            return
+                methodRef != null
+                && methodRef.DeclaringType.FullName == this.ToType.FullName
+                && methodRef.Name == this.MethodName;
+        }
+    }
+}

src/StardewModdingAPI/Metadata/InstructionMetadata.cs

@@ -90,7 +90,10 @@ namespace StardewModdingAPI.Metadata
                 new FieldReplaceRewriter(typeof(Game1), "smoothFont", nameof(Game1.smallFont)),
 
                 // SMAPI 1.9
-                new TypeReferenceRewriter("StardewModdingAPI.Inheritance.ItemStackChange", typeof(ItemStackChange))
+                new TypeReferenceRewriter("StardewModdingAPI.Inheritance.ItemStackChange", typeof(ItemStackChange)),
+
+                // SMAPI 2.0
+                new VirtualEntryCallRemover() // Mod.Entry changed from virtual to abstract in SMAPI 2.0, which breaks the few mods which called base.Entry()
             };
         }
     }

src/StardewModdingAPI/StardewModdingAPI.csproj

@@ -104,6 +104,7 @@
     <Compile Include="Framework\ModLoading\RewriteHelper.cs" />
     <Compile Include="Framework\ModLoading\Rewriters\FieldReplaceRewriter.cs" />
     <Compile Include="Framework\ModLoading\Rewriters\FieldToPropertyRewriter.cs" />
+    <Compile Include="Framework\ModLoading\Rewriters\VirtualEntryCallRemover.cs" />
     <Compile Include="Framework\ModLoading\Rewriters\MethodParentRewriter.cs" />
     <Compile Include="Framework\ModLoading\Rewriters\TypeReferenceRewriter.cs" />
     <Compile Include="Framework\ModLoading\Rewriters\Wrappers\SpriteBatchWrapper.cs" />