chore: Warn about unsupported async return types

src/Agent/NewRelic/Agent/Core/Wrapper/WrapperService.cs

@@ -10,6 +10,8 @@
 using NewRelic.Agent.Core.Utilities;
 using NewRelic.Agent.Extensions.Logging;
 using NewRelic.Agent.Api;
+using System.Reflection;
+using System.Threading.Tasks;
 
 namespace NewRelic.Agent.Core.Wrapper
 {
@@ -88,6 +90,23 @@ public AfterWrappedMethodDelegate BeforeWrappedMethod(Type type, string methodNa
  return null;
  }
 
+ if (isAsync)
+ {
+ try
+ {
+ var returnType = type.GetMethod(methodName, BindingFlags.Public | BindingFlags.NonPublic | BindingFlags.Instance | BindingFlags.Static).ReturnType;
+ if ((returnType != typeof(Task)) &&
+ (!returnType.IsGenericType || (returnType.GetGenericTypeDefinition() != typeof(Task<>))))
+ {
+ Log.Warn("Instrumenting async methods that return a type other than Task or Task<> is not supported and may result in inconsistent data. '{0}' has a return type of '{1}'.", methodName, returnType?.Name);
+ }
+ }
+ catch
+ {
+ // Since this is just for logging purposes it doesn't matter if it fails
+ }
+ }
+
  _functionIdToWrapper[functionId] = new InstrumentedMethodInfoWrapper(instrumentedMethodInfo, trackedWrapper);
  GenerateLibraryVersionSupportabilityMetric(instrumentedMethodInfo);
  }