reorganise repo structure

25 files changed, 2071 insertions, 0 deletions

diff --git a/src/SMAPI/Framework/ModLoading/AssemblyDefinitionResolver.cs b/src/SMAPI/Framework/ModLoading/AssemblyDefinitionResolver.cs
new file mode 100644
index 00000000..4378798c
--- /dev/null
+++ b/src/SMAPI/Framework/ModLoading/AssemblyDefinitionResolver.cs
@@ -0,0 +1,61 @@
+using System.Collections.Generic;
+using Mono.Cecil;
+
+namespace StardewModdingAPI.Framework.ModLoading
+{
+    /// <summary>A minimal assembly definition resolver which resolves references to known assemblies.</summary>
+    internal class AssemblyDefinitionResolver : DefaultAssemblyResolver
+    {
+        /*********
+        ** Properties
+        *********/
+        /// <summary>The known assemblies.</summary>
+        private readonly IDictionary<string, AssemblyDefinition> Loaded = new Dictionary<string, AssemblyDefinition>();
+
+
+        /*********
+        ** Public methods
+        *********/
+        /// <summary>Add known assemblies to the resolver.</summary>
+        /// <param name="assemblies">The known assemblies.</param>
+        public void Add(params AssemblyDefinition[] assemblies)
+        {
+            foreach (AssemblyDefinition assembly in assemblies)
+            {
+                this.Loaded[assembly.Name.Name] = assembly;
+                this.Loaded[assembly.Name.FullName] = assembly;
+            }
+        }
+
+        /// <summary>Resolve an assembly reference.</summary>
+        /// <param name="name">The assembly name.</param>
+        public override AssemblyDefinition Resolve(AssemblyNameReference name) => this.ResolveName(name.Name) ?? base.Resolve(name);
+
+        /// <summary>Resolve an assembly reference.</summary>
+        /// <param name="name">The assembly name.</param>
+        /// <param name="parameters">The assembly reader parameters.</param>
+        public override AssemblyDefinition Resolve(AssemblyNameReference name, ReaderParameters parameters) => this.ResolveName(name.Name) ?? base.Resolve(name, parameters);
+
+        /// <summary>Resolve an assembly reference.</summary>
+        /// <param name="fullName">The assembly full name (including version, etc).</param>
+        public override AssemblyDefinition Resolve(string fullName) => this.ResolveName(fullName) ?? base.Resolve(fullName);
+
+        /// <summary>Resolve an assembly reference.</summary>
+        /// <param name="fullName">The assembly full name (including version, etc).</param>
+        /// <param name="parameters">The assembly reader parameters.</param>
+        public override AssemblyDefinition Resolve(string fullName, ReaderParameters parameters) => this.ResolveName(fullName) ?? base.Resolve(fullName, parameters);
+
+
+        /*********
+        ** Private methods
+        *********/
+        /// <summary>Resolve a known assembly definition based on its short or full name.</summary>
+        /// <param name="name">The assembly's short or full name.</param>
+        private AssemblyDefinition ResolveName(string name)
+        {
+            return this.Loaded.ContainsKey(name)
+                ? this.Loaded[name]
+                : null;
+        }
+    }
+}
diff --git a/src/SMAPI/Framework/ModLoading/AssemblyLoadStatus.cs b/src/SMAPI/Framework/ModLoading/AssemblyLoadStatus.cs
new file mode 100644
index 00000000..11be19fc
--- /dev/null
+++ b/src/SMAPI/Framework/ModLoading/AssemblyLoadStatus.cs
@@ -0,0 +1,15 @@
+namespace StardewModdingAPI.Framework.ModLoading
+{
+    /// <summary>Indicates the result of an assembly load.</summary>
+    internal enum AssemblyLoadStatus
+    {
+        /// <summary>The assembly was loaded successfully.</summary>
+        Okay = 1,
+
+        /// <summary>The assembly could not be loaded.</summary>
+        Failed = 2,
+
+        /// <summary>The assembly is already loaded.</summary>
+        AlreadyLoaded = 3
+    }
+}
diff --git a/src/SMAPI/Framework/ModLoading/AssemblyLoader.cs b/src/SMAPI/Framework/ModLoading/AssemblyLoader.cs
new file mode 100644
index 00000000..1e3c4a05
--- /dev/null
+++ b/src/SMAPI/Framework/ModLoading/AssemblyLoader.cs
@@ -0,0 +1,333 @@
+using System;
+using System.Collections.Generic;
+using System.IO;
+using System.Linq;
+using System.Reflection;
+using Mono.Cecil;
+using Mono.Cecil.Cil;
+using StardewModdingAPI.Framework.Exceptions;
+using StardewModdingAPI.Metadata;
+
+namespace StardewModdingAPI.Framework.ModLoading
+{
+    /// <summary>Preprocesses and loads mod assemblies.</summary>
+    internal class AssemblyLoader
+    {
+        /*********
+        ** Properties
+        *********/
+        /// <summary>Metadata for mapping assemblies to the current platform.</summary>
+        private readonly PlatformAssemblyMap AssemblyMap;
+
+        /// <summary>A type => assembly lookup for types which should be rewritten.</summary>
+        private readonly IDictionary<string, Assembly> TypeAssemblies;
+
+        /// <summary>Encapsulates monitoring and logging.</summary>
+        private readonly IMonitor Monitor;
+
+        /// <summary>Whether to enable developer mode logging.</summary>
+        private readonly bool IsDeveloperMode;
+
+
+        /*********
+        ** Public methods
+        *********/
+        /// <summary>Construct an instance.</summary>
+        /// <param name="targetPlatform">The current game platform.</param>
+        /// <param name="monitor">Encapsulates monitoring and logging.</param>
+        /// <param name="isDeveloperMode">Whether to enable developer mode logging.</param>
+        public AssemblyLoader(Platform targetPlatform, IMonitor monitor, bool isDeveloperMode)
+        {
+            this.Monitor = monitor;
+            this.IsDeveloperMode = isDeveloperMode;
+            this.AssemblyMap = Constants.GetAssemblyMap(targetPlatform);
+
+            // generate type => assembly lookup for types which should be rewritten
+            this.TypeAssemblies = new Dictionary<string, Assembly>();
+            foreach (Assembly assembly in this.AssemblyMap.Targets)
+            {
+                ModuleDefinition module = this.AssemblyMap.TargetModules[assembly];
+                foreach (TypeDefinition type in module.GetTypes())
+                {
+                    if (!type.IsPublic)
+                        continue; // no need to rewrite
+                    if (type.Namespace.Contains("<"))
+                        continue; // ignore assembly metadata
+                    this.TypeAssemblies[type.FullName] = assembly;
+                }
+            }
+        }
+
+        /// <summary>Preprocess and load an assembly.</summary>
+        /// <param name="mod">The mod for which the assembly is being loaded.</param>
+        /// <param name="assemblyPath">The assembly file path.</param>
+        /// <param name="assumeCompatible">Assume the mod is compatible, even if incompatible code is detected.</param>
+        /// <returns>Returns the rewrite metadata for the preprocessed assembly.</returns>
+        /// <exception cref="IncompatibleInstructionException">An incompatible CIL instruction was found while rewriting the assembly.</exception>
+        public Assembly Load(IModMetadata mod, string assemblyPath, bool assumeCompatible)
+        {
+            // get referenced local assemblies
+            AssemblyParseResult[] assemblies;
+            {
+                AssemblyDefinitionResolver resolver = new AssemblyDefinitionResolver();
+                HashSet<string> visitedAssemblyNames = new HashSet<string>(AppDomain.CurrentDomain.GetAssemblies().Select(p => p.GetName().Name)); // don't try loading assemblies that are already loaded
+                assemblies = this.GetReferencedLocalAssemblies(new FileInfo(assemblyPath), visitedAssemblyNames, resolver).ToArray();
+            }
+
+            // validate load
+            if (!assemblies.Any() || assemblies[0].Status == AssemblyLoadStatus.Failed)
+            {
+                throw new SAssemblyLoadFailedException(!File.Exists(assemblyPath)
+                    ? $"Could not load '{assemblyPath}' because it doesn't exist."
+                    : $"Could not load '{assemblyPath}'."
+                );
+            }
+            if (assemblies.Last().Status == AssemblyLoadStatus.AlreadyLoaded) // mod assembly is last in dependency order
+                throw new SAssemblyLoadFailedException($"Could not load '{assemblyPath}' because it was already loaded. Do you have two copies of this mod?");
+
+            // rewrite & load assemblies in leaf-to-root order
+            bool oneAssembly = assemblies.Length == 1;
+            Assembly lastAssembly = null;
+            HashSet<string> loggedMessages = new HashSet<string>();
+            foreach (AssemblyParseResult assembly in assemblies)
+            {
+                if (assembly.Status == AssemblyLoadStatus.AlreadyLoaded)
+                    continue;
+
+                bool changed = this.RewriteAssembly(mod, assembly.Definition, assumeCompatible, loggedMessages, logPrefix: "   ");
+                if (changed)
+                {
+                    if (!oneAssembly)
+                        this.Monitor.Log($"   Loading {assembly.File.Name} (rewritten in memory)...", LogLevel.Trace);
+                    using (MemoryStream outStream = new MemoryStream())
+                    {
+                        assembly.Definition.Write(outStream);
+                        byte[] bytes = outStream.ToArray();
+                        lastAssembly = Assembly.Load(bytes);
+                    }
+                }
+                else
+                {
+                    if (!oneAssembly)
+                        this.Monitor.Log($"   Loading {assembly.File.Name}...", LogLevel.Trace);
+                    lastAssembly = Assembly.UnsafeLoadFrom(assembly.File.FullName);
+                }
+            }
+
+            // last assembly loaded is the root
+            return lastAssembly;
+        }
+
+        /// <summary>Resolve an assembly by its name.</summary>
+        /// <param name="name">The assembly name.</param>
+        /// <remarks>
+        /// This implementation returns the first loaded assembly which matches the short form of
+        /// the assembly name, to resolve assembly resolution issues when rewriting
+        /// assemblies (especially with Mono). Since this is meant to be called on <see cref="AppDomain.AssemblyResolve"/>,
+        /// the implicit assumption is that loading the exact assembly failed.
+        /// </remarks>
+        public Assembly ResolveAssembly(string name)
+        {
+            string shortName = name.Split(new[] { ',' }, 2).First(); // get simple name (without version and culture)
+            return AppDomain.CurrentDomain
+                .GetAssemblies()
+                .FirstOrDefault(p => p.GetName().Name == shortName);
+        }
+
+
+        /*********
+        ** Private methods
+        *********/
+        /****
+        ** Assembly parsing
+        ****/
+        /// <summary>Get a list of referenced local assemblies starting from the mod assembly, ordered from leaf to root.</summary>
+        /// <param name="file">The assembly file to load.</param>
+        /// <param name="visitedAssemblyNames">The assembly names that should be skipped.</param>
+        /// <param name="assemblyResolver">A resolver which resolves references to known assemblies.</param>
+        /// <returns>Returns the rewrite metadata for the preprocessed assembly.</returns>
+        private IEnumerable<AssemblyParseResult> GetReferencedLocalAssemblies(FileInfo file, HashSet<string> visitedAssemblyNames, IAssemblyResolver assemblyResolver)
+        {
+            // validate
+            if (file.Directory == null)
+                throw new InvalidOperationException($"Could not get directory from file path '{file.FullName}'.");
+            if (!file.Exists)
+                yield break; // not a local assembly
+
+            // read assembly
+            byte[] assemblyBytes = File.ReadAllBytes(file.FullName);
+            AssemblyDefinition assembly;
+            using (Stream readStream = new MemoryStream(assemblyBytes))
+                assembly = AssemblyDefinition.ReadAssembly(readStream, new ReaderParameters(ReadingMode.Deferred) { AssemblyResolver = assemblyResolver });
+
+            // skip if already visited
+            if (visitedAssemblyNames.Contains(assembly.Name.Name))
+                yield return new AssemblyParseResult(file, null, AssemblyLoadStatus.AlreadyLoaded);
+            visitedAssemblyNames.Add(assembly.Name.Name);
+
+            // yield referenced assemblies
+            foreach (AssemblyNameReference dependency in assembly.MainModule.AssemblyReferences)
+            {
+                FileInfo dependencyFile = new FileInfo(Path.Combine(file.Directory.FullName, $"{dependency.Name}.dll"));
+                foreach (AssemblyParseResult result in this.GetReferencedLocalAssemblies(dependencyFile, visitedAssemblyNames, assemblyResolver))
+                    yield return result;
+            }
+
+            // yield assembly
+            yield return new AssemblyParseResult(file, assembly, AssemblyLoadStatus.Okay);
+        }
+
+        /****
+        ** Assembly rewriting
+        ****/
+        /// <summary>Rewrite the types referenced by an assembly.</summary>
+        /// <param name="mod">The mod for which the assembly is being loaded.</param>
+        /// <param name="assembly">The assembly to rewrite.</param>
+        /// <param name="assumeCompatible">Assume the mod is compatible, even if incompatible code is detected.</param>
+        /// <param name="loggedMessages">The messages that have already been logged for this mod.</param>
+        /// <param name="logPrefix">A string to prefix to log messages.</param>
+        /// <returns>Returns whether the assembly was modified.</returns>
+        /// <exception cref="IncompatibleInstructionException">An incompatible CIL instruction was found while rewriting the assembly.</exception>
+        private bool RewriteAssembly(IModMetadata mod, AssemblyDefinition assembly, bool assumeCompatible, HashSet<string> loggedMessages, string logPrefix)
+        {
+            ModuleDefinition module = assembly.MainModule;
+            string filename = $"{assembly.Name.Name}.dll";
+
+            // swap assembly references if needed (e.g. XNA => MonoGame)
+            bool platformChanged = false;
+            for (int i = 0; i < module.AssemblyReferences.Count; i++)
+            {
+                // remove old assembly reference
+                if (this.AssemblyMap.RemoveNames.Any(name => module.AssemblyReferences[i].Name == name))
+                {
+                    this.Monitor.LogOnce(loggedMessages, $"{logPrefix}Rewriting {filename} for OS...");
+                    platformChanged = true;
+                    module.AssemblyReferences.RemoveAt(i);
+                    i--;
+                }
+            }
+            if (platformChanged)
+            {
+                // add target assembly references
+                foreach (AssemblyNameReference target in this.AssemblyMap.TargetReferences.Values)
+                    module.AssemblyReferences.Add(target);
+
+                // rewrite type scopes to use target assemblies
+                IEnumerable<TypeReference> typeReferences = module.GetTypeReferences().OrderBy(p => p.FullName);
+                foreach (TypeReference type in typeReferences)
+                    this.ChangeTypeScope(type);
+            }
+
+            // find (and optionally rewrite) incompatible instructions
+            bool anyRewritten = false;
+            IInstructionHandler[] handlers = new InstructionMetadata().GetHandlers().ToArray();
+            foreach (MethodDefinition method in this.GetMethods(module))
+            {
+                // check method definition
+                foreach (IInstructionHandler handler in handlers)
+                {
+                    InstructionHandleResult result = handler.Handle(module, method, this.AssemblyMap, platformChanged);
+                    this.ProcessInstructionHandleResult(mod, handler, result, loggedMessages, logPrefix, assumeCompatible, filename);
+                    if (result == InstructionHandleResult.Rewritten)
+                        anyRewritten = true;
+                }
+
+                // check CIL instructions
+                ILProcessor cil = method.Body.GetILProcessor();
+                foreach (Instruction instruction in cil.Body.Instructions.ToArray())
+                {
+                    foreach (IInstructionHandler handler in handlers)
+                    {
+                        InstructionHandleResult result = handler.Handle(module, cil, instruction, this.AssemblyMap, platformChanged);
+                        this.ProcessInstructionHandleResult(mod, handler, result, loggedMessages, logPrefix, assumeCompatible, filename);
+                        if (result == InstructionHandleResult.Rewritten)
+                            anyRewritten = true;
+                    }
+                }
+            }
+
+            return platformChanged || anyRewritten;
+        }
+
+        /// <summary>Process the result from an instruction handler.</summary>
+        /// <param name="mod">The mod being analysed.</param>
+        /// <param name="handler">The instruction handler.</param>
+        /// <param name="result">The result returned by the handler.</param>
+        /// <param name="loggedMessages">The messages already logged for the current mod.</param>
+        /// <param name="assumeCompatible">Assume the mod is compatible, even if incompatible code is detected.</param>
+        /// <param name="logPrefix">A string to prefix to log messages.</param>
+        /// <param name="filename">The assembly filename for log messages.</param>
+        private void ProcessInstructionHandleResult(IModMetadata mod, IInstructionHandler handler, InstructionHandleResult result, HashSet<string> loggedMessages, string logPrefix, bool assumeCompatible, string filename)
+        {
+            switch (result)
+            {
+                case InstructionHandleResult.Rewritten:
+                    this.Monitor.LogOnce(loggedMessages, $"{logPrefix}Rewrote {filename} to fix {handler.NounPhrase}...");
+                    break;
+
+                case InstructionHandleResult.NotCompatible:
+                    if (!assumeCompatible)
+                        throw new IncompatibleInstructionException(handler.NounPhrase, $"Found an incompatible CIL instruction ({handler.NounPhrase}) while loading assembly {filename}.");
+                    this.Monitor.LogOnce(loggedMessages, $"{logPrefix}Found an incompatible CIL instruction ({handler.NounPhrase}) while loading assembly {filename}, but SMAPI is configured to allow it anyway. The mod may crash or behave unexpectedly.", LogLevel.Warn);
+                    break;
+
+                case InstructionHandleResult.DetectedGamePatch:
+                    this.Monitor.LogOnce(loggedMessages, $"{logPrefix}Detected game patcher ({handler.NounPhrase}) in assembly {filename}.");
+                    this.Monitor.LogOnce(loggedMessages, $"{mod.DisplayName} patches the game, which may impact game stability. If you encounter problems, try removing this mod first.", LogLevel.Warn);
+                    break;
+
+                case InstructionHandleResult.DetectedSaveSerialiser:
+                    this.Monitor.LogOnce(loggedMessages, $"{logPrefix}Detected possible save serialiser change ({handler.NounPhrase}) in assembly {filename}.");
+                    this.Monitor.LogOnce(loggedMessages, $"{mod.DisplayName} seems to change the save serialiser. It may change your saves in such a way that they won't work without this mod in the future.", LogLevel.Warn);
+                    break;
+
+                case InstructionHandleResult.DetectedDynamic:
+                    this.Monitor.LogOnce(loggedMessages, $"{logPrefix}Detected 'dynamic' keyword ({handler.NounPhrase}) in assembly {filename}.");
+                    this.Monitor.LogOnce(loggedMessages, $"{mod.DisplayName} uses the 'dynamic' keyword, which isn't compatible with Stardew Valley on Linux or Mac.",
+#if SMAPI_FOR_WINDOWS
+                        this.IsDeveloperMode ? LogLevel.Warn : LogLevel.Debug
+#else
+                        LogLevel.Warn
+#endif
+                    );
+                    break;
+
+                case InstructionHandleResult.None:
+                    break;
+
+                default:
+                    throw new NotSupportedException($"Unrecognised instruction handler result '{result}'.");
+            }
+        }
+
+        /// <summary>Get the correct reference to use for compatibility with the current platform.</summary>
+        /// <param name="type">The type reference to rewrite.</param>
+        private void ChangeTypeScope(TypeReference type)
+        {
+            // check skip conditions
+            if (type == null || type.FullName.StartsWith("System."))
+                return;
+
+            // get assembly
+            if (!this.TypeAssemblies.TryGetValue(type.FullName, out Assembly assembly))
+                return;
+
+            // replace scope
+            AssemblyNameReference assemblyRef = this.AssemblyMap.TargetReferences[assembly];
+            type.Scope = assemblyRef;
+        }
+
+        /// <summary>Get all methods in a module.</summary>
+        /// <param name="module">The module to search.</param>
+        private IEnumerable<MethodDefinition> GetMethods(ModuleDefinition module)
+        {
+            return (
+                from type in module.GetTypes()
+                where type.HasMethods
+                from method in type.Methods
+                where method.HasBody
+                select method
+            );
+        }
+    }
+}
diff --git a/src/SMAPI/Framework/ModLoading/AssemblyParseResult.cs b/src/SMAPI/Framework/ModLoading/AssemblyParseResult.cs
new file mode 100644
index 00000000..b56a776c
--- /dev/null
+++ b/src/SMAPI/Framework/ModLoading/AssemblyParseResult.cs
@@ -0,0 +1,36 @@
+using System.IO;
+using Mono.Cecil;
+
+namespace StardewModdingAPI.Framework.ModLoading
+{
+    /// <summary>Metadata about a parsed assembly definition.</summary>
+    internal class AssemblyParseResult
+    {
+        /*********
+        ** Accessors
+        *********/
+        /// <summary>The original assembly file.</summary>
+        public readonly FileInfo File;
+
+        /// <summary>The assembly definition.</summary>
+        public readonly AssemblyDefinition Definition;
+
+        /// <summary>The result of the assembly load.</summary>
+        public AssemblyLoadStatus Status;
+
+
+        /*********
+        ** Public methods
+        *********/
+        /// <summary>Construct an instance.</summary>
+        /// <param name="file">The original assembly file.</param>
+        /// <param name="assembly">The assembly definition.</param>
+        /// <param name="status">The result of the assembly load.</param>
+        public AssemblyParseResult(FileInfo file, AssemblyDefinition assembly, AssemblyLoadStatus status)
+        {
+            this.File = file;
+            this.Definition = assembly;
+            this.Status = status;
+        }
+    }
+}
diff --git a/src/SMAPI/Framework/ModLoading/Finders/EventFinder.cs b/src/SMAPI/Framework/ModLoading/Finders/EventFinder.cs
new file mode 100644
index 00000000..e4beb7a9
--- /dev/null
+++ b/src/SMAPI/Framework/ModLoading/Finders/EventFinder.cs
@@ -0,0 +1,82 @@
+using Mono.Cecil;
+using Mono.Cecil.Cil;
+
+namespace StardewModdingAPI.Framework.ModLoading.Finders
+{
+    /// <summary>Finds incompatible CIL instructions that reference a given event.</summary>
+    internal class EventFinder : IInstructionHandler
+    {
+        /*********
+        ** Properties
+        *********/
+        /// <summary>The full type name for which to find references.</summary>
+        private readonly string FullTypeName;
+
+        /// <summary>The event name for which to find references.</summary>
+        private readonly string EventName;
+
+        /// <summary>The result to return for matching instructions.</summary>
+        private readonly InstructionHandleResult Result;
+
+
+        /*********
+        ** Accessors
+        *********/
+        /// <summary>A brief noun phrase indicating what the instruction finder matches.</summary>
+        public string NounPhrase { get; }
+
+
+        /*********
+        ** Public methods
+        *********/
+        /// <summary>Construct an instance.</summary>
+        /// <param name="fullTypeName">The full type name for which to find references.</param>
+        /// <param name="eventName">The event name for which to find references.</param>
+        /// <param name="result">The result to return for matching instructions.</param>
+        public EventFinder(string fullTypeName, string eventName, InstructionHandleResult result)
+        {
+            this.FullTypeName = fullTypeName;
+            this.EventName = eventName;
+            this.Result = result;
+            this.NounPhrase = $"{fullTypeName}.{eventName} event";
+        }
+
+        /// <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 virtual 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 virtual InstructionHandleResult Handle(ModuleDefinition module, ILProcessor cil, Instruction instruction, PlatformAssemblyMap assemblyMap, bool platformChanged)
+        {
+            return this.IsMatch(instruction)
+                ? this.Result
+                : InstructionHandleResult.None;
+        }
+
+
+        /*********
+        ** 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.FullTypeName
+                && (methodRef.Name == "add_" + this.EventName || methodRef.Name == "remove_" + this.EventName);
+        }
+    }
+}
diff --git a/src/SMAPI/Framework/ModLoading/Finders/FieldFinder.cs b/src/SMAPI/Framework/ModLoading/Finders/FieldFinder.cs
new file mode 100644
index 00000000..00805815
--- /dev/null
+++ b/src/SMAPI/Framework/ModLoading/Finders/FieldFinder.cs
@@ -0,0 +1,82 @@
+using Mono.Cecil;
+using Mono.Cecil.Cil;
+
+namespace StardewModdingAPI.Framework.ModLoading.Finders
+{
+    /// <summary>Finds incompatible CIL instructions that reference a given field.</summary>
+    internal class FieldFinder : IInstructionHandler
+    {
+        /*********
+        ** Properties
+        *********/
+        /// <summary>The full type name for which to find references.</summary>
+        private readonly string FullTypeName;
+
+        /// <summary>The field name for which to find references.</summary>
+        private readonly string FieldName;
+
+        /// <summary>The result to return for matching instructions.</summary>
+        private readonly InstructionHandleResult Result;
+
+
+        /*********
+        ** Accessors
+        *********/
+        /// <summary>A brief noun phrase indicating what the instruction finder matches.</summary>
+        public string NounPhrase { get; }
+
+
+        /*********
+        ** Public methods
+        *********/
+        /// <summary>Construct an instance.</summary>
+        /// <param name="fullTypeName">The full type name for which to find references.</param>
+        /// <param name="fieldName">The field name for which to find references.</param>
+        /// <param name="result">The result to return for matching instructions.</param>
+        public FieldFinder(string fullTypeName, string fieldName, InstructionHandleResult result)
+        {
+            this.FullTypeName = fullTypeName;
+            this.FieldName = fieldName;
+            this.Result = result;
+            this.NounPhrase = $"{fullTypeName}.{fieldName} field";
+        }
+
+        /// <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 virtual 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 virtual InstructionHandleResult Handle(ModuleDefinition module, ILProcessor cil, Instruction instruction, PlatformAssemblyMap assemblyMap, bool platformChanged)
+        {
+            return this.IsMatch(instruction)
+                ? this.Result
+                : InstructionHandleResult.None;
+        }
+
+
+        /*********
+        ** Protected methods
+        *********/