merge CIL finders & rewriters into one interface (#254)

3 files changed, 47 insertions, 27 deletions

diff --git a/src/StardewModdingAPI.AssemblyRewriters/Rewriters/FieldReplaceRewriter.cs b/src/StardewModdingAPI.AssemblyRewriters/Rewriters/FieldReplaceRewriter.cs
index ffd22e7c..95663c49 100644
--- a/src/StardewModdingAPI.AssemblyRewriters/Rewriters/FieldReplaceRewriter.cs
+++ b/src/StardewModdingAPI.AssemblyRewriters/Rewriters/FieldReplaceRewriter.cs
@@ -7,16 +7,13 @@ using StardewModdingAPI.AssemblyRewriters.Finders;
 namespace StardewModdingAPI.AssemblyRewriters.Rewriters
 {
     /// <summary>Rewrites references to one field with another.</summary>
-    public class FieldReplaceRewriter : FieldFinder, IInstructionRewriter
+    public class FieldReplaceRewriter : FieldFinder
     {
         /*********
         ** Properties
         *********/
-        /// <summary>The type whose field to which references should be rewritten.</summary>
-        private readonly Type Type;
-
-        /// <summary>The new field name to reference.</summary>
-        private readonly string ToFieldName;
+        /// <summary>The new field to reference.</summary>
+        private readonly FieldInfo ToField;
 
 
         /*********
@@ -30,8 +27,9 @@ namespace StardewModdingAPI.AssemblyRewriters.Rewriters
         public FieldReplaceRewriter(Type type, string fromFieldName, string toFieldName, string nounPhrase = null)
             : base(type.FullName, fromFieldName, nounPhrase)
         {
-            this.Type = type;
-            this.ToFieldName = toFieldName;
+            this.ToField = type.GetField(toFieldName);
+            if (this.ToField == null)
+                throw new InvalidOperationException($"The {type.FullName} class doesn't have a {toFieldName} field.");
         }
 
         /// <summary>Rewrite a CIL instruction for compatibility.</summary>
@@ -39,13 +37,17 @@ namespace StardewModdingAPI.AssemblyRewriters.Rewriters
         /// <param name="cil">The CIL rewriter.</param>
         /// <param name="instruction">The instruction to rewrite.</param>
         /// <param name="assemblyMap">Metadata for mapping assemblies to the current platform.</param>
-        public void Rewrite(ModuleDefinition module, ILProcessor cil, Instruction instruction, PlatformAssemblyMap assemblyMap)
+        /// <param name="platformChanged">Whether the mod was compiled on a different platform.</param>
+        /// <returns>Returns whether the instruction was rewritten.</returns>
+        /// <exception cref="IncompatibleInstructionException">The CIL instruction is not compatible, and can't be rewritten.</exception>
+        public override bool Rewrite(ModuleDefinition module, ILProcessor cil, Instruction instruction, PlatformAssemblyMap assemblyMap, bool platformChanged)
         {
-            FieldInfo field = this.Type.GetField(this.ToFieldName);
-            if (field == null)
-                throw new InvalidOperationException($"The {this.Type.FullName} class doesn't have a {this.ToFieldName} field.");
-            FieldReference newRef = module.Import(field);
+            if (!this.IsMatch(instruction, platformChanged))
+                return false;
+
+            FieldReference newRef = module.Import(this.ToField);
             cil.Replace(instruction, cil.Create(instruction.OpCode, newRef));
+            return true;
         }
     }
 }
diff --git a/src/StardewModdingAPI.AssemblyRewriters/Rewriters/FieldToPropertyRewriter.cs b/src/StardewModdingAPI.AssemblyRewriters/Rewriters/FieldToPropertyRewriter.cs
index f2f99cc1..a25f3fef 100644
--- a/src/StardewModdingAPI.AssemblyRewriters/Rewriters/FieldToPropertyRewriter.cs
+++ b/src/StardewModdingAPI.AssemblyRewriters/Rewriters/FieldToPropertyRewriter.cs
@@ -6,7 +6,7 @@ using StardewModdingAPI.AssemblyRewriters.Finders;
 namespace StardewModdingAPI.AssemblyRewriters.Rewriters
 {
     /// <summary>Rewrites field references into property references.</summary>
-    public class FieldToPropertyRewriter : FieldFinder, IInstructionRewriter
+    public class FieldToPropertyRewriter : FieldFinder
     {
         /*********
         ** Properties
@@ -37,11 +37,18 @@ namespace StardewModdingAPI.AssemblyRewriters.Rewriters
         /// <param name="cil">The CIL rewriter.</param>
         /// <param name="instruction">The instruction to rewrite.</param>
         /// <param name="assemblyMap">Metadata for mapping assemblies to the current platform.</param>
-        public void Rewrite(ModuleDefinition module, ILProcessor cil, Instruction instruction, PlatformAssemblyMap assemblyMap)
+        /// <param name="platformChanged">Whether the mod was compiled on a different platform.</param>
+        /// <returns>Returns whether the instruction was rewritten.</returns>
+        /// <exception cref="IncompatibleInstructionException">The CIL instruction is not compatible, and can't be rewritten.</exception>
+        public override bool Rewrite(ModuleDefinition module, ILProcessor cil, Instruction instruction, PlatformAssemblyMap assemblyMap, bool platformChanged)
         {
+            if (!this.IsMatch(instruction, platformChanged))
+                return false;
+
             string methodPrefix = instruction.OpCode == OpCodes.Ldsfld || instruction.OpCode == OpCodes.Ldfld ? "get" : "set";
             MethodReference propertyRef = module.Import(this.Type.GetMethod($"{methodPrefix}_{this.FieldName}"));
             cil.Replace(instruction, cil.Create(OpCodes.Call, propertyRef));
+            return true;
         }
     }
 }
diff --git a/src/StardewModdingAPI.AssemblyRewriters/Rewriters/MethodParentRewriter.cs b/src/StardewModdingAPI.AssemblyRewriters/Rewriters/MethodParentRewriter.cs
index 24d4dff9..3ec8c704 100644
--- a/src/StardewModdingAPI.AssemblyRewriters/Rewriters/MethodParentRewriter.cs
+++ b/src/StardewModdingAPI.AssemblyRewriters/Rewriters/MethodParentRewriter.cs
@@ -43,10 +43,32 @@ namespace StardewModdingAPI.AssemblyRewriters.Rewriters
             this.OnlyIfPlatformChanged = onlyIfPlatformChanged;
         }
 
+        /// <summary>Rewrite a CIL instruction for compatibility.</summary>
+        /// <param name="module">The module being rewritten.</param>
+        /// <param name="cil">The CIL rewriter.</param>
+        /// <param name="instruction">The instruction to rewrite.</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>
+        /// <returns>Returns whether the instruction was rewritten.</returns>
+        /// <exception cref="IncompatibleInstructionException">The CIL instruction is not compatible, and can't be rewritten.</exception>
+        public bool Rewrite(ModuleDefinition module, ILProcessor cil, Instruction instruction, PlatformAssemblyMap assemblyMap, bool platformChanged)
+        {
+            if (!this.IsMatch(instruction, platformChanged))
+                return false;
+
+            MethodReference methodRef = (MethodReference)instruction.Operand;
+            methodRef.DeclaringType = module.Import(this.ToType);
+            return true;
+        }
+
+
+        /*********
+        ** Protected methods
+        *********/
         /// <summary>Get whether a CIL instruction matches.</summary>
         /// <param name="instruction">The IL instruction.</param>
         /// <param name="platformChanged">Whether the mod was compiled on a different platform.</param>
-        public bool IsMatch(Instruction instruction, bool platformChanged)
+        protected bool IsMatch(Instruction instruction, bool platformChanged)
         {
             MethodReference methodRef = RewriteHelper.AsMethodReference(instruction);
             return
@@ -55,16 +77,5 @@ namespace StardewModdingAPI.AssemblyRewriters.Rewriters
                 && methodRef.DeclaringType.FullName == this.FromType.FullName
                 && RewriteHelper.HasMatchingSignature(this.ToType, methodRef);
         }
-
-        /// <summary>Rewrite a CIL instruction for compatibility.</summary>
-        /// <param name="module">The module being rewritten.</param>
-        /// <param name="cil">The CIL rewriter.</param>
-        /// <param name="instruction">The instruction to rewrite.</param>
-        /// <param name="assemblyMap">Metadata for mapping assemblies to the current platform.</param>
-        public void Rewrite(ModuleDefinition module, ILProcessor cil, Instruction instruction, PlatformAssemblyMap assemblyMap)
-        {
-            MethodReference methodRef = (MethodReference)instruction.Operand;
-            methodRef.DeclaringType = module.Import(this.ToType);
-        }
     }
 }