Make mod loading non nullable, set certain properties to be read only after init (#506)

* Make mod loading non nullable, set certain properties to be read only after init

- Breaks all mods, will require new nugets

* Make mod assembly list IEnumerable

* Convert checks to IsNullOrEmpty

* Update comment, enforce ModGuid

SPTarkov.Server/Modding/ModDllLoader.cs

@@ -53,14 +53,12 @@ public class ModDllLoader
     /// <returns>SptMod</returns>
     private static SptMod LoadMod(string path)
     {
-        var result = new SptMod { Directory = path, Assemblies = [] };
-        var assemblyCount = 0;
+        List<Assembly> assemblyList = [];
         foreach (var file in new DirectoryInfo(path).GetFiles()) // Only search top level
         {
             if (string.Equals(file.Extension, ".dll", StringComparison.OrdinalIgnoreCase))
             {
-                assemblyCount++;
-                result.Assemblies.Add(
+                assemblyList.Add(
                     AssemblyLoadContext.Default.LoadFromAssemblyPath(
                         Path.GetFullPath(file.FullName)
                     )
@@ -68,30 +66,29 @@ public class ModDllLoader
             }
         }
 
-        if (assemblyCount == 0)
+        if (assemblyList.Count == 0)
         {
             throw new Exception($"No Assemblies found in path: {Path.GetFullPath(path)}");
         }
 
-        result.ModMetadata = LoadModMetadata(result.Assemblies, path);
-
-        if (result.ModMetadata == null)
+        SptMod result = new()
         {
-            throw new Exception(
-                $"Failed to load mod metadata for: {Path.GetFullPath(path)} \ndid you override `AbstractModMetadata`?"
-            );
-        }
+            Directory = path,
+            Assemblies = assemblyList,
+            ModMetadata = LoadModMetadata(assemblyList, path),
+        };
 
         if (
-            result.ModMetadata?.Name == null
-            || result.ModMetadata?.Author == null
-            || result.ModMetadata?.Version == null
-            || result.ModMetadata?.Licence == null
-            || result.ModMetadata?.SptVersion == null
+            string.IsNullOrEmpty(result.ModMetadata.ModGuid)
+            || string.IsNullOrEmpty(result.ModMetadata.Name)
+            || string.IsNullOrEmpty(result.ModMetadata.Author)
+            || string.IsNullOrEmpty(result.ModMetadata.Version)
+            || string.IsNullOrEmpty(result.ModMetadata.License)
+            || string.IsNullOrEmpty(result.ModMetadata.SptVersion)
         )
         {
             throw new Exception(
-                $"The mod metadata for: {Path.GetFullPath(path)} is missing one of these properties: name, author, licence, version or sptVersion"
+                $"The mod metadata for: {Path.GetFullPath(path)} is missing one of these properties: ModGuid, Name, Author, License, Version or SptVersion"
             );
         }
 
@@ -105,7 +102,7 @@ public class ModDllLoader
     /// <param name="path">Path of the mod directory</param>
     /// <returns>Mod metadata</returns>
     /// <exception cref="Exception">Thrown if duplicate metadata implementations are found</exception>
-    private static AbstractModMetadata? LoadModMetadata(List<Assembly> assemblies, string path)
+    private static AbstractModMetadata LoadModMetadata(List<Assembly> assemblies, string path)
     {
         AbstractModMetadata? result = null;
 
@@ -131,6 +128,13 @@ public class ModDllLoader
             }
         }
 
+        if (result == null)
+        {
+            throw new Exception(
+                $"Failed to load mod metadata for: {Path.GetFullPath(path)} \ndid you override `AbstractModMetadata`?"
+            );
+        }
+
         return result;
     }
 }