Allow for an output binding value of an invocation result to be null (#10698)

In a successful invocation, the output binding is now allowed to be null and will no longer throw an exception.

Author: satvu

release_notes.md

@@ -3,6 +3,7 @@
 <!-- Please add your release notes in the following format:
 - My change description (#PR)
 -->
+- Allow for an output binding value of an invocation result to be null (#10698)
 - Updated dotnet-isolated worker to 1.0.12.
   - [Corrected the path for the prelaunch app location.](https://github.com/Azure/azure-functions-dotnet-worker/pull/2897)
-  - [Added net9 prelaunch app.](https://github.com/Azure/azure-functions-dotnet-worker/pull/2898)
+  - [Added net9 prelaunch app.](https://github.com/Azure/azure-functions-dotnet-worker/pull/2898)

src/WebJobs.Script.Grpc/Channel/GrpcWorkerChannel.cs

@@ -1068,8 +1068,10 @@ private async Task<object> GetBindingDataAsync(ParameterBinding binding, string
                 case ParameterBindingType.Data:
                     // Data was transferred by the worker using RPC
                     return binding.Data.ToObject();
+                case ParameterBindingType.None:
+                    return null;
                 default:
-                    throw new InvalidOperationException("Unknown ParameterBindingType");
+                    throw new InvalidOperationException($"Unknown ParameterBindingType of type {binding.RpcDataCase}");
             }
         }
 

test/WebJobs.Script.Tests/Workers/Rpc/GrpcWorkerChannelTests.cs

@@ -1546,6 +1546,20 @@ await TestHelpers.Await(() => GetInvocationLogs().Length == logLoop,
             }
         }
 
+        [Fact]
+        public async Task NullOutputBinding_DoesNotThrow()
+        {
+            await CreateDefaultWorkerChannel();
+
+            var invocationId = Guid.NewGuid();
+            var resultSource = new TaskCompletionSource<ScriptInvocationResult>();
+            ScriptInvocationContext scriptInvocationContext = GetTestScriptInvocationContext(invocationId, resultSource, logger: _logger);
+            await _workerChannel.SendInvocationRequest(scriptInvocationContext);
+            await _workerChannel.InvokeResponse(BuildSuccessfulInvocationResponseWithNullOutputBinding(invocationId.ToString()));
+
+            Assert.Equal(TaskStatus.RanToCompletion, resultSource.Task.Status);
+        }
+
         private static IEnumerable<FunctionMetadata> GetTestFunctionsList(string runtime, bool addWorkerProperties = false)
         {
             return GetTestFunctionsList(runtime, numberOfFunctions: 2, addWorkerProperties);
@@ -1690,6 +1704,30 @@ private static InvocationResponse BuildSuccessfulInvocationResponse(string invoc
             };
         }
 
+        private InvocationResponse BuildSuccessfulInvocationResponseWithNullOutputBinding(string invocationId)
+        {
+            StatusResult statusResult = new StatusResult()
+            {
+                Status = StatusResult.Types.Status.Success
+            };
+
+            ParameterBinding parameterBinding = new ParameterBinding()
+            {
+                Name = "output1",
+                Data = null
+            };
+
+            InvocationResponse invocationResponse = new InvocationResponse()
+            {
+                InvocationId = invocationId == null ? "TestInvocationId" : invocationId,
+                Result = statusResult
+            };
+
+            invocationResponse.OutputData.Add(parameterBinding);
+
+            return invocationResponse;
+        }
+
         private static FunctionMetadata BuildFunctionMetadataForHttpTrigger(string name, string language = null)
         {
             var functionMetadata = new FunctionMetadata() { Name = name, Language = language };