fix 'unknown mod' deprecation warnings when they occur in the Mod constructor

docs/release-notes.md

@@ -5,6 +5,7 @@
   * Added mod page link to 'missing dependency' errors for the most common dependencies.
   * Restrict to Stardew Valley 1.3.33 or earlier (to avoid confusion when SDV 1.3.35 is released).
   * Fixed 'unknown mod' deprecation warnings showing a stack trace when developers mode not enabled.
+  * Fixed 'unknown mod' deprecation warnings when they occur in the Mod constructor.
 
 * For modders:
   * Fixed `Constants.SaveFolderName` and `CurrentSavePath` not available during early load stages when using `Specialised.LoadStageChanged` event.

src/SMAPI/Framework/ModRegistry.cs

@@ -33,8 +33,14 @@ namespace StardewModdingAPI.Framework
         public void Add(IModMetadata metadata)
         {
             this.Mods.Add(metadata);
-            if (!metadata.IsContentPack)
-                this.ModNamesByAssembly[metadata.Mod.GetType().Assembly.FullName] = metadata;
+        }
+
+        /// <summary>Track a mod's assembly for use via <see cref="GetFrom"/>.</summary>
+        /// <param name="metadata">The mod metadata.</param>
+        /// <param name="modAssembly">The mod assembly.</param>
+        public void TrackAssemblies(IModMetadata metadata, Assembly modAssembly)
+        {
+            this.ModNamesByAssembly[modAssembly.FullName] = metadata;
         }
 
         /// <summary>Get metadata for all loaded mods.</summary>

src/SMAPI/Framework/SCore.cs

@@ -977,6 +977,7 @@ namespace StardewModdingAPI.Framework
                 try
                 {
                     modAssembly = assemblyLoader.Load(mod, assemblyPath, assumeCompatible: mod.DataRecord?.Status == ModStatus.AssumeCompatible);
+                    this.ModRegistry.TrackAssemblies(mod, modAssembly);
                 }
                 catch (IncompatibleInstructionException) // details already in trace logs
                 {