Moved most TypeInfo module validation logic from CommandService.

src/Discord.Net.Commands/Extensions/TypeInfoExtensions.cs

@@ -0,0 +1,97 @@
+using Discord.Logging;
+using System;
+using System.Linq;
+using System.Reflection;
+using System.Threading.Tasks;
+
+namespace Discord.Commands
+{
+    internal static class TypeInfoExtensions
+    {
+        public static async Task<bool> IsValidModuleType(this TypeInfo typeInfo, bool autoLoadable = false, Logger logger = null)
+        {
+            if(IsOuterSubTypeCandidate(typeInfo, out Type parentType))
+            {
+                return await IsValidOuterSubTypeAsync(typeInfo, parentType, autoLoadable, logger);
+            }
+            else
+            {
+                return await IsModuleAsync(typeInfo, logger, autoLoadable);
+            }
+        }
+
+        public static bool IsOuterSubTypeCandidate(this TypeInfo typeInfo, out Type parentType)
+        {
+            var groupAttr = typeInfo.GetCustomAttribute<GroupAttribute>();
+            if (groupAttr != null)
+            {
+                if (groupAttr.ParentModule != null)
+                {
+                    parentType = groupAttr.ParentModule;
+                    return true;
+                }
+            }
+            parentType = null;
+            return false;
+        }
+
+
+        /// <param name="autoLoadable">If true, must not contain [DontAutoLoad] or will return false.</param>
+        public static async Task<bool> IsValidOuterSubTypeAsync(this TypeInfo typeInfo, Type parentType, bool autoLoadable = false, Logger logger = null)
+        {
+            TypeInfo parentTypeInfo = parentType.GetTypeInfo();
+
+            bool targetValid = await IsModuleAsync(typeInfo, logger, autoLoadable);
+            if (targetValid)
+            {
+                bool parentValid = await IsModuleAsync(parentTypeInfo, logger, autoLoadable);
+                if (!parentValid)
+                {
+                    if (logger != null)
+                    {
+                        await logger.WarningAsync($"Parent Class {parentTypeInfo.FullName} is not a module. Group module {typeInfo.FullName} was not loaded.").ConfigureAwait(false);
+                    }
+                    return false;
+                }
+            }
+            return targetValid;
+        }
+
+        private static async Task<bool> IsModuleAsync(TypeInfo typeInfo, Logger logger, bool autoLoadable)
+        {
+            if(IsValidModuleDefinition(typeInfo))
+            {
+                if (autoLoadable)
+                {
+                    if (typeInfo.IsPublic || typeInfo.IsNestedPublic)
+                    {
+                        return !typeInfo.IsDefined(typeof(DontAutoLoadAttribute));
+                    }
+                    else if (IsAutoLoadableModuleCandidate(typeInfo))
+                    {
+                        if(logger != null)
+                        {
+                            await logger.WarningAsync($"Class {typeInfo.FullName} is not public and cannot be loaded. To suppress this message, mark the class with {nameof(DontAutoLoadAttribute)}.").ConfigureAwait(false);
+                        }
+                    }
+                }
+                else
+                {
+                    return true;
+                }
+            }
+
+            return false;
+        }
+
+        internal static bool IsValidModuleDefinition(this TypeInfo typeInfo) =>
+            ModuleClassBuilder.ModuleTypeInfo.IsAssignableFrom(typeInfo) &&
+                   !typeInfo.IsAbstract &&
+                   !typeInfo.ContainsGenericParameters;
+
+        private static bool IsAutoLoadableModuleCandidate(TypeInfo typeInfo) =>
+            typeInfo.DeclaredMethods.Any(
+                x => x.GetCustomAttribute<CommandAttribute>() != null) &&
+                    typeInfo.GetCustomAttribute<DontAutoLoadAttribute>() == null;
+    }
+}