add support for casting mod-provided API to an interface without a direct assembly reference (#409)

build/common.targets

@@ -86,6 +86,7 @@
     <Copy SourceFiles="$(TargetDir)\StardewModdingAPI.AssemblyRewriters.dll" DestinationFolder="$(GamePath)" />
     <Copy SourceFiles="$(TargetDir)\$(TargetName).pdb" DestinationFolder="$(GamePath)" />
     <Copy SourceFiles="$(TargetDir)\$(TargetName).xml" DestinationFolder="$(GamePath)" />
+    <Copy SourceFiles="$(TargetDir)\ImpromptuInterface.dll" DestinationFolder="$(GamePath)" />
     <Copy SourceFiles="$(TargetDir)\Newtonsoft.Json.dll" DestinationFolder="$(GamePath)" />
     <Copy SourceFiles="$(TargetDir)\Mono.Cecil.dll" DestinationFolder="$(GamePath)" />
   </Target>

build/prepare-install-package.targets

@@ -22,6 +22,7 @@
     <Copy SourceFiles="$(TargetDir)\readme.txt" DestinationFiles="$(PackagePath)\README.txt" />
     
     <!-- copy SMAPI files for Mono -->
+    <Copy Condition="$(OS) != 'Windows_NT'" SourceFiles="$(CompiledSmapiPath)\ImpromptuInterface.dll" DestinationFolder="$(PackageInternalPath)\Mono" />
     <Copy Condition="$(OS) != 'Windows_NT'" SourceFiles="$(CompiledSmapiPath)\Mono.Cecil.dll" DestinationFolder="$(PackageInternalPath)\Mono" />
     <Copy Condition="$(OS) != 'Windows_NT'" SourceFiles="$(CompiledSmapiPath)\Newtonsoft.Json.dll" DestinationFolder="$(PackageInternalPath)\Mono" />
     <Copy Condition="$(OS) != 'Windows_NT'" SourceFiles="$(CompiledSmapiPath)\StardewModdingAPI.exe" DestinationFolder="$(PackageInternalPath)\Mono" />
@@ -36,6 +37,7 @@
     <Copy Condition="$(OS) != 'Windows_NT'" SourceFiles="@(CompiledMods)" DestinationFolder="$(PackageInternalPath)\Mono\Mods\%(RecursiveDir)" />
 
     <!-- copy SMAPI files for Windows -->
+    <Copy Condition="$(OS) == 'Windows_NT'" SourceFiles="$(CompiledSmapiPath)\ImpromptuInterface.dll" DestinationFolder="$(PackageInternalPath)\Windows" />
     <Copy Condition="$(OS) == 'Windows_NT'" SourceFiles="$(CompiledSmapiPath)\Mono.Cecil.dll" DestinationFolder="$(PackageInternalPath)\Windows" />
     <Copy Condition="$(OS) == 'Windows_NT'" SourceFiles="$(CompiledSmapiPath)\Newtonsoft.Json.dll" DestinationFolder="$(PackageInternalPath)\Windows" />
     <Copy Condition="$(OS) == 'Windows_NT'" SourceFiles="$(CompiledSmapiPath)\StardewModdingAPI.exe" DestinationFolder="$(PackageInternalPath)\Windows" />

src/SMAPI/Framework/ModHelpers/ModRegistryHelper.cs

@@ -1,5 +1,6 @@
 using System.Collections.Generic;
 using System.Linq;
+using ImpromptuInterface;
 
 namespace StardewModdingAPI.Framework.ModHelpers
 {
@@ -62,5 +63,28 @@ namespace StardewModdingAPI.Framework.ModHelpers
                 this.Monitor.Log($"Accessed mod-provided API for {mod.DisplayName}.", LogLevel.Trace);
             return mod?.Api;
         }
+
+        /// <summary>Get the API provided by a mod, mapped to a given interface which specifies the expected properties and methods. If the mod has no API or it's not compatible with the given interface, get <c>null</c>.</summary>
+        /// <typeparam name="TInterface">The interface which matches the properties and methods you intend to access.</typeparam>
+        /// <param name="uniqueID">The mod's unique ID.</param>
+        public TInterface GetApi<TInterface>(string uniqueID) where TInterface : class
+        {
+            // validate
+            if (!typeof(TInterface).IsInterface)
+            {
+                this.Monitor.Log("Tried to map a mod-provided API into a class; must be an interface.");
+                return null;
+            }
+
+            // get raw API
+            object api = this.GetApi(uniqueID);
+            if (api == null)
+                return null;
+
+            // get API of type
+            if (api is TInterface castApi)
+                return castApi;
+            return api.ActLike<TInterface>();
+        }
     }
 }

src/SMAPI/IModRegistry.cs

@@ -20,5 +20,10 @@ namespace StardewModdingAPI
         /// <summary>Get the API provided by a mod, or <c>null</c> if it has none. This signature requires using the <see cref="IModHelper.Reflection"/> API to access the API's properties and methods.</summary>
         /// <param name="uniqueID">The mod's unique ID.</param>
         object GetApi(string uniqueID);
+
+        /// <summary>Get the API provided by a mod, mapped to a given interface which specifies the expected properties and methods. If the mod has no API or it's not compatible with the given interface, get <c>null</c>.</summary>
+        /// <typeparam name="TInterface">The interface which matches the properties and methods you intend to access.</typeparam>
+        /// <param name="uniqueID">The mod's unique ID.</param>
+        TInterface GetApi<TInterface>(string uniqueID) where TInterface : class;
     }
 }

src/SMAPI/StardewModdingAPI.csproj

@@ -53,6 +53,9 @@
     <ApplicationIcon>icon.ico</ApplicationIcon>
   </PropertyGroup>
   <ItemGroup>
+    <Reference Include="ImpromptuInterface, Version=6.2.2.0, Culture=neutral, PublicKeyToken=0b1781c923b2975b, processorArchitecture=MSIL">
+      <HintPath>..\packages\ImpromptuInterface.6.2.2\lib\net40\ImpromptuInterface.dll</HintPath>
+    </Reference>
     <Reference Include="Mono.Cecil, Version=0.9.6.0, Culture=neutral, PublicKeyToken=0738eb9f132ed756, processorArchitecture=MSIL">
       <HintPath>..\packages\Mono.Cecil.0.9.6.4\lib\net45\Mono.Cecil.dll</HintPath>
       <Private>True</Private>

src/SMAPI/packages.config

@@ -1,5 +1,6 @@
 <?xml version="1.0" encoding="utf-8"?>
 <packages>
+  <package id="ImpromptuInterface" version="6.2.2" targetFramework="net45" />
   <package id="Mono.Cecil" version="0.9.6.4" targetFramework="net45" />
   <package id="Newtonsoft.Json" version="10.0.3" targetFramework="net45" />
 </packages>