Support inherited handler methods

Author: ejsmith

src/Foundatio.Mediator/HandlerAnalyzer.cs

@@ -84,8 +84,7 @@ public static List<HandlerInfo> GetHandlers(GeneratorSyntaxContext context)
 
         bool treatAsHandlerClass = nameMatches || implementsMarker || hasClassHandlerAttribute;
 
-        var handlerMethods = classSymbol.GetMembers()
-            .OfType<IMethodSymbol>()
+        var handlerMethods = GetMethods(classSymbol)
             .Where(m => IsHandlerMethod(m, context.SemanticModel.Compilation, treatAsHandlerClass))
             .ToList();
 
@@ -174,6 +173,32 @@ private static bool IsHandlerMethod(IMethodSymbol method, Compilation compilatio
         return true;
     }
 
+    private static IEnumerable<IMethodSymbol> GetMethods(INamedTypeSymbol targetSymbol, bool includeBaseMethods = true)
+    {
+        var methods = new Dictionary<string, IMethodSymbol>();
+
+        var currentSymbol = targetSymbol;
+
+        while (currentSymbol != null)
+        {
+            var methodSymbols = currentSymbol
+                .GetMembers()
+                .Where(m => m.Kind == SymbolKind.Method)
+                .OfType<IMethodSymbol>()
+                .Where(p => !methods.ContainsKey(p.Name));
+
+            foreach (var methodSymbol in methodSymbols)
+                methods.Add(methodSymbol.Name, methodSymbol);
+
+            if (!includeBaseMethods)
+                break;
+
+            currentSymbol = currentSymbol.BaseType;
+        }
+
+        return methods.Values;
+    }
+
     private static readonly string[] ValidHandlerMethodNames = [
         "Handle", "HandleAsync",
         "Handles", "HandlesAsync",

tests/Foundatio.Mediator.Tests/OpenGenericHandlerTests.cs

@@ -5,15 +5,18 @@ namespace Foundatio.Mediator.Tests;
 public record UpdateEntity<T>(T Entity) : ICommand;
 public record UpdateEntityPair<T1, T2>(T1 First, T2 Second) : ICommand;
 
-public class EntityHandler<T>
+public class EntityHandlerBase<T>
 {
-    public Task HandleAsync(UpdateEntity<T> command, CancellationToken cancellationToken)
+    public Task HandlesAsync(UpdateEntity<T> command, CancellationToken cancellationToken)
     {
-        // no-op
         return Task.CompletedTask;
     }
 }
 
+public class EntityHandler<T> : EntityHandlerBase<T>
+{
+}
+
 public class EntityPairHandler<T1, T2>
 {
     public Task HandleAsync(UpdateEntityPair<T1, T2> command, CancellationToken cancellationToken)