Store MethodInfo when creating an ActivityDefinition

src/Temporalio/Activities/ActivityDefinition.cs

@@ -19,13 +19,15 @@ private ActivityDefinition(
             Type returnType,
             IReadOnlyCollection<Type> parameterTypes,
             int requiredParameterCount,
-            Func<object?[], object?> invoker)
+            Func<object?[], object?> invoker,
+            MethodInfo? methodInfo)
         {
             Name = name;
             ReturnType = returnType;
             ParameterTypes = parameterTypes;
             RequiredParameterCount = requiredParameterCount;
             this.invoker = invoker;
+            MethodInfo = methodInfo;
         }
 
         /// <summary>
@@ -56,6 +58,11 @@ private ActivityDefinition(
         /// </summary>
         public bool Dynamic => Name == null;
 
+        /// <summary>
+        /// Gets the <see cref="MethodInfo"/>. Will only have a value if one was used to create this <see cref="ActivityDefinition"/>.
+        /// </summary>
+        public MethodInfo? MethodInfo { get; private init; }
+
         /// <summary>
         /// Create an activity definition from a delegate. <see cref="Delegate.DynamicInvoke" /> is
         /// called on this delegate. The delegate must have an associated method and that method
@@ -89,31 +96,7 @@ public static ActivityDefinition Create(
             int requiredParameterCount,
             Func<object?[], object?> invoker)
         {
-            // If there is a null name, which means dynamic, there must only be one parameter type
-            // and it must be varargs IRawValue
-            if (name == null && (
-                requiredParameterCount != 1 ||
-                parameterTypes.SingleOrDefault() != typeof(Converters.IRawValue[])))
-            {
-                throw new ArgumentException(
-                    $"Dynamic activity must accept a required array of IRawValue");
-            }
-
-            if (requiredParameterCount > parameterTypes.Count)
-            {
-                throw new ArgumentException(
-                    $"Activity {name} has more required parameters than parameters",
-                    nameof(requiredParameterCount));
-            }
-            foreach (var parameterType in parameterTypes)
-            {
-                if (parameterType.IsByRef)
-                {
-                    throw new ArgumentException(
-                        $"Activity {name} has disallowed ref/out parameter");
-                }
-            }
-            return new(name, returnType, parameterTypes, requiredParameterCount, invoker);
+            return Create(name, returnType, parameterTypes, requiredParameterCount, invoker, methodInfo: null);
         }
 
         /// <summary>
@@ -136,7 +119,8 @@ public static ActivityDefinition Create(MethodInfo method, Func<object?[], objec
                 method.ReturnType,
                 parms.Select(p => p.ParameterType).ToArray(),
                 parms.Count(p => !p.HasDefaultValue),
-                parameters => invoker.Invoke(ParametersWithDefaults(parms, parameters)));
+                parameters => invoker.Invoke(ParametersWithDefaults(parms, parameters)),
+                method);
         }
 
         /// <summary>
@@ -300,5 +284,40 @@ internal static string NameFromMethodForCall(MethodInfo method)
             }
             return name;
         }
+
+        private static ActivityDefinition Create(
+            string? name,
+            Type returnType,
+            IReadOnlyCollection<Type> parameterTypes,
+            int requiredParameterCount,
+            Func<object?[], object?> invoker,
+            MethodInfo? methodInfo)
+        {
+            // If there is a null name, which means dynamic, there must only be one parameter type
+            // and it must be varargs IRawValue
+            if (name == null && (
+                requiredParameterCount != 1 ||
+                parameterTypes.SingleOrDefault() != typeof(Converters.IRawValue[])))
+            {
+                throw new ArgumentException(
+                    $"Dynamic activity must accept a required array of IRawValue");
+            }
+
+            if (requiredParameterCount > parameterTypes.Count)
+            {
+                throw new ArgumentException(
+                    $"Activity {name} has more required parameters than parameters",
+                    nameof(requiredParameterCount));
+            }
+            foreach (var parameterType in parameterTypes)
+            {
+                if (parameterType.IsByRef)
+                {
+                    throw new ArgumentException(
+                        $"Activity {name} has disallowed ref/out parameter");
+                }
+            }
+            return new(name, returnType, parameterTypes, requiredParameterCount, invoker, methodInfo);
+        }
     }
 }

tests/Temporalio.Tests/Activities/ActivityDefinitionTests.cs

@@ -1,5 +1,6 @@
 namespace Temporalio.Tests.Activities;
 
+using System.Reflection;
 using System.Threading.Tasks;
 using Temporalio.Activities;
 using Temporalio.Converters;
@@ -173,6 +174,40 @@ public async Task CreateAll_ClosedGeneric_CanInvoke()
         Assert.Equal("some-val", await defn.InvokeAsync(Array.Empty<object?>()));
     }
 
+    [Fact]
+    public async Task Create_WithMethodInfo_HasValidMethodInfo()
+    {
+        var methodInfo = typeof(ActivityDefinitionTests)
+            .GetMethods(BindingFlags.NonPublic | BindingFlags.Static)
+            .Single(mi => mi.Name.Equals(nameof(GoodAct1Async), StringComparison.Ordinal));
+
+        var defn = ActivityDefinition.Create(methodInfo, objects => methodInfo!.Invoke(this, objects));
+        Assert.Equal(methodInfo, defn.MethodInfo);
+    }
+
+    [Fact]
+    public async Task Create_WithDelegate_HasValidMethodInfo()
+    {
+        var methodInfo = typeof(ActivityDefinitionTests)
+            .GetMethods(BindingFlags.NonPublic | BindingFlags.Static)
+            .Single(mi => mi.Name.Equals(nameof(GoodAct1Async), StringComparison.Ordinal));
+
+        var defn = ActivityDefinition.Create(GoodAct1Async);
+        Assert.Equal(methodInfo, defn.MethodInfo);
+    }
+
+    [Fact]
+    public async Task Create_WithLambda_DoesNotHaveValidMethodInfo()
+    {
+        var defn = ActivityDefinition.Create(
+            "some-name",
+            typeof(int),
+            new Type[] { typeof(int) },
+            1,
+            parameters => ((int)parameters[0]!) + 5);
+        Assert.Null(defn.MethodInfo);
+    }
+
     protected static void BadAct1()
     {
     }