add EarlyConstants for constants needed before external DLLs are loaded

3 files changed, 44 insertions, 29 deletions

diff --git a/src/SMAPI/Constants.cs b/src/SMAPI/Constants.cs
index c1c99150..b7977fb7 100644
--- a/src/SMAPI/Constants.cs
+++ b/src/SMAPI/Constants.cs
@@ -5,11 +5,42 @@ using System.Reflection;
 using StardewModdingAPI.Enums;
 using StardewModdingAPI.Framework;
 using StardewModdingAPI.Framework.ModLoading;
+using StardewModdingAPI.Toolkit.Framework;
 using StardewModdingAPI.Toolkit.Utilities;
 using StardewValley;
 
 namespace StardewModdingAPI
 {
+    /// <summary>Contains constants that are accessed before the game itself has been loaded.</summary>
+    /// <remarks>Most code should use <see cref="Constants"/> instead of this class directly.</remarks>
+    internal static class EarlyConstants
+    {
+        //
+        // Note: this class *must not* depend on any external DLL beyond .NET Framework itself.
+        // That includes the game or SMAPI toolkit, since it's accessed before those are loaded.
+        //
+        // Adding an external dependency may seem to work in some cases, but will prevent SMAPI
+        // from showing a human-readable error if the game isn't available. To test this, just
+        // rename "Stardew Valley.exe" in the game folder; you should see an error like "Oops!
+        // SMAPI can't find the game", not a technical exception.
+        //
+
+        /*********
+        ** Accessors
+        *********/
+        /// <summary>The path to the game folder.</summary>
+        public static string ExecutionPath { get; } = Path.GetDirectoryName(Assembly.GetExecutingAssembly().Location);
+
+        /// <summary>The absolute path to the folder containing SMAPI's internal files.</summary>
+        public static readonly string InternalFilesPath = Path.Combine(EarlyConstants.ExecutionPath, "smapi-internal");
+
+        /// <summary>The target game platform.</summary>
+        internal static GamePlatform Platform { get; } = (GamePlatform)Enum.Parse(typeof(GamePlatform), LowLevelEnvironmentUtility.DetectPlatform());
+
+        /// <summary>The game's assembly name.</summary>
+        internal static string GameAssemblyName => EarlyConstants.Platform == GamePlatform.Windows ? "Stardew Valley" : "StardewValley";
+    }
+
     /// <summary>Contains SMAPI's constants and assumptions.</summary>
     public static class Constants
     {
@@ -29,10 +60,10 @@ namespace StardewModdingAPI
         public static ISemanticVersion MaximumGameVersion { get; } = null;
 
         /// <summary>The target game platform.</summary>
-        public static GamePlatform TargetPlatform => (GamePlatform)Constants.Platform;
+        public static GamePlatform TargetPlatform { get; } = EarlyConstants.Platform;
 
         /// <summary>The path to the game folder.</summary>
-        public static string ExecutionPath { get; } = Path.GetDirectoryName(Assembly.GetExecutingAssembly().Location);
+        public static string ExecutionPath { get; } = EarlyConstants.ExecutionPath;
 
         /// <summary>The directory path containing Stardew Valley's app data.</summary>
         public static string DataPath { get; } = Path.Combine(Environment.GetFolderPath(Environment.SpecialFolder.ApplicationData), "StardewValley");
@@ -67,7 +98,7 @@ namespace StardewModdingAPI
         internal const string GamePerformanceCounterName = "<StardewValley>";
 
         /// <summary>The absolute path to the folder containing SMAPI's internal files.</summary>
-        internal static readonly string InternalFilesPath = Program.DllSearchPath;
+        internal static readonly string InternalFilesPath = EarlyConstants.InternalFilesPath;
 
         /// <summary>The file path for the SMAPI configuration file.</summary>
         internal static string ApiConfigPath => Path.Combine(Constants.InternalFilesPath, "config.json");
@@ -105,11 +136,8 @@ namespace StardewModdingAPI
         /// <summary>The game's current semantic version.</summary>
         internal static ISemanticVersion GameVersion { get; } = new GameVersion(Game1.version);
 
-        /// <summary>The target game platform.</summary>
-        internal static Platform Platform { get; } = EnvironmentUtility.DetectPlatform();
-
-        /// <summary>The game's assembly name.</summary>
-        internal static string GameAssemblyName => Constants.Platform == Platform.Windows ? "Stardew Valley" : "StardewValley";
+        /// <summary>The target game platform as a SMAPI toolkit constant.</summary>
+        internal static Platform Platform { get; } = (Platform)Constants.TargetPlatform;
 
         /// <summary>The language code for non-translated mod assets.</summary>
         internal static LocalizedContentManager.LanguageCode DefaultLanguage { get; } = LocalizedContentManager.LanguageCode.en;
diff --git a/src/SMAPI/Program.cs b/src/SMAPI/Program.cs
index a8f20c69..05251070 100644
--- a/src/SMAPI/Program.cs
+++ b/src/SMAPI/Program.cs
@@ -1,13 +1,9 @@
 using System;
-using System.Diagnostics.CodeAnalysis;
 using System.IO;
 using System.Linq;
 using System.Reflection;
 using System.Threading;
-#if SMAPI_FOR_WINDOWS
-#endif
 using StardewModdingAPI.Framework;
-using StardewModdingAPI.Toolkit.Utilities;
 
 namespace StardewModdingAPI
 {
@@ -18,9 +14,7 @@ namespace StardewModdingAPI
         ** Fields
         *********/
         /// <summary>The absolute path to search for SMAPI's internal DLLs.</summary>
-        /// <remarks>We can't use <see cref="Constants.ExecutionPath"/> directly, since <see cref="Constants"/> depends on DLLs loaded from this folder.</remarks>
-        [SuppressMessage("ReSharper", "AssignNullToNotNullAttribute", Justification = "The assembly location is never null in this context.")]
-        internal static readonly string DllSearchPath = Path.Combine(Path.GetDirectoryName(Assembly.GetExecutingAssembly().Location), "smapi-internal");
+        internal static readonly string DllSearchPath = EarlyConstants.InternalFilesPath;
 
 
         /*********
@@ -37,10 +31,9 @@ namespace StardewModdingAPI
                 Program.AssertGameVersion();
                 Program.Start(args);
             }
-            catch (BadImageFormatException ex) when (ex.FileName == "StardewValley" || ex.FileName == "Stardew Valley") // NOTE: don't use StardewModdingAPI.Constants here, assembly resolution isn't hooked up at this point
+            catch (BadImageFormatException ex) when (ex.FileName == "StardewValley" || ex.FileName == "Stardew Valley") // don't use EarlyConstants.GameAssemblyName, since we want to check both possible names
             {
-                string executableName = Program.GetExecutableAssemblyName();
-                Console.WriteLine($"SMAPI failed to initialize because your game's {executableName}.exe seems to be invalid.\nThis may be a pirated version which modified the executable in an incompatible way; if so, you can try a different download or buy a legitimate version.\n\nTechnical details:\n{ex}");
+                Console.WriteLine($"SMAPI failed to initialize because your game's {ex.FileName}.exe seems to be invalid.\nThis may be a pirated version which modified the executable in an incompatible way; if so, you can try a different download or buy a legitimate version.\n\nTechnical details:\n{ex}");
             }
             catch (Exception ex)
             {
@@ -76,11 +69,10 @@ namespace StardewModdingAPI
         }
 
         /// <summary>Assert that the game is available.</summary>
-        /// <remarks>This must be checked *before* any references to <see cref="Constants"/>, and this method should not reference <see cref="Constants"/> itself to avoid errors in Mono.</remarks>
+        /// <remarks>This must be checked *before* any references to <see cref="Constants"/>, and this method should not reference <see cref="Constants"/> itself to avoid errors in Mono or when the game isn't present.</remarks>
         private static void AssertGamePresent()
         {
-            string gameAssemblyName = Program.GetExecutableAssemblyName();
-            if (Type.GetType($"StardewValley.Game1, {gameAssemblyName}", throwOnError: false) == null)
+            if (Type.GetType($"StardewValley.Game1, {EarlyConstants.GameAssemblyName}", throwOnError: false) == null)
                 Program.PrintErrorAndExit("Oops! SMAPI can't find the game. Make sure you're running StardewModdingAPI.exe in your game folder. See the readme.txt file for details.");
         }
 
@@ -100,14 +92,6 @@ namespace StardewModdingAPI
             // max version
             else if (Constants.MaximumGameVersion != null && Constants.GameVersion.IsNewerThan(Constants.MaximumGameVersion))
                 Program.PrintErrorAndExit($"Oops! You're running Stardew Valley {Constants.GameVersion}, but this version of SMAPI is only compatible up to Stardew Valley {Constants.MaximumGameVersion}. Please check for a newer version of SMAPI: https://smapi.io.");
-
-        }
-
-        /// <summary>Get the game's executable assembly name.</summary>
-        private static string GetExecutableAssemblyName()
-        {
-            Platform platform = EnvironmentUtility.DetectPlatform();
-            return platform == Platform.Windows ? "Stardew Valley" : "StardewValley";
         }
 
         /// <summary>Initialize SMAPI and launch the game.</summary>
diff --git a/src/SMAPI/SMAPI.csproj b/src/SMAPI/SMAPI.csproj
index a3dbf52f..7d2b8199 100644
--- a/src/SMAPI/SMAPI.csproj
+++ b/src/SMAPI/SMAPI.csproj
@@ -59,8 +59,11 @@
   <ItemGroup>
     <Content Include="SMAPI.config.json" CopyToOutputDirectory="PreserveNewest" />
     <Content Include="..\SMAPI.Web\wwwroot\SMAPI.metadata.json" Link="SMAPI.metadata.json" CopyToOutputDirectory="PreserveNewest" />
+
     <None Update="i18n\*" CopyToOutputDirectory="PreserveNewest" />
     <None Update="steam_appid.txt" CopyToOutputDirectory="PreserveNewest" />
+
+    <Compile Include="..\SMAPI.Toolkit\Framework\LowLevelEnvironmentUtility.cs" Link="Framework\Utilities\LowLevelEnvironmentUtility.cs" />
   </ItemGroup>
 
   <Import Project="..\SMAPI.Internal\SMAPI.Internal.projitems" Label="Shared" />