reject mods which reference obsolete StardewModdingAPI.Extensions class (#247)

src/StardewModdingAPI.AssemblyRewriters/Finders/SMAPI_Extensions_MethodFinder.cs

@@ -0,0 +1,31 @@
+using System.Diagnostics.CodeAnalysis;
+using Mono.Cecil;
+using Mono.Cecil.Cil;
+using StardewModdingAPI.AssemblyRewriters.Framework;
+
+namespace StardewModdingAPI.AssemblyRewriters.Finders
+{
+    /// <summary>Matches CIL instructions that reference the former <c>StardewModdingAPI.Extensions</c> class, which was removed in SMAPI 1.9.</summary>
+    [SuppressMessage("ReSharper", "InconsistentNaming", Justification = "This class is not meant to be used directly, and is deliberately named to make it easier to know what it changes at a glance.")]
+    public class SMAPI_Extensions_MethodFinder : BaseMethodFinder
+    {
+        /*********
+        ** Accessors
+        *********/
+        /// <summary>A brief noun phrase indicating what the instruction finder matches.</summary>
+        public override string NounPhrase { get; } = "obsolete StardewModdingAPI.Extensions API";
+
+
+        /*********
+        ** Protected methods
+        *********/
+        /// <summary>Get whether a method reference should be rewritten.</summary>
+        /// <param name="instruction">The IL instruction.</param>
+        /// <param name="methodRef">The method reference.</param>
+        /// <param name="platformChanged">Whether the mod was compiled on a different platform.</param>
+        protected override bool IsMatch(Instruction instruction, MethodReference methodRef, bool platformChanged)
+        {
+            return methodRef.DeclaringType.FullName == "StardewModdingAPI.Extensions";
+        }
+    }
+}

src/StardewModdingAPI.AssemblyRewriters/StardewModdingAPI.AssemblyRewriters.csproj

@@ -66,6 +66,7 @@
     <Compile Include="..\GlobalAssemblyInfo.cs">
       <Link>Properties\GlobalAssemblyInfo.cs</Link>
     </Compile>
+    <Compile Include="Finders\SMAPI_Extensions_MethodFinder.cs" />
     <Compile Include="Framework\BaseFieldFinder.cs" />
     <Compile Include="Framework\BaseMethodFinder.cs" />
     <Compile Include="IInstructionRewriter.cs" />

src/StardewModdingAPI/Constants.cs

@@ -4,6 +4,7 @@ using System.IO;
 using System.Linq;
 using System.Reflection;
 using StardewModdingAPI.AssemblyRewriters;
+using StardewModdingAPI.AssemblyRewriters.Finders;
 using StardewModdingAPI.AssemblyRewriters.Rewriters.Crossplatform;
 using StardewModdingAPI.AssemblyRewriters.Rewriters.SDV1_2;
 using StardewValley;
@@ -140,6 +141,8 @@ namespace StardewModdingAPI
         {
             return new IInstructionFinder[]
             {
+                // APIs removed in SMAPI 1.9
+                new SMAPI_Extensions_MethodFinder()
             };
         }