Add Nexus support to ContextPropagation sample

Author: cretz

.editorconfig

@@ -98,6 +98,7 @@ dotnet_diagnostic.SA1513.severity = none
 dotnet_diagnostic.SA1515.severity = none
 
 # Do not require XML doc in samples
+dotnet_diagnostic.CS1591.severity = none
 dotnet_diagnostic.SA1600.severity = none
 dotnet_diagnostic.SA1602.severity = none
 

.gitignore

@@ -7,3 +7,4 @@ obj/
 /.vs
 /.vscode
 /.idea
+.claude/

Directory.Build.props

@@ -5,10 +5,8 @@
     <Authors>Temporal</Authors>
     <ContinuousIntegrationBuild Condition="'$(GITHUB_ACTIONS)' == 'true'">true</ContinuousIntegrationBuild>
     <EnableNETAnalyzers>true</EnableNETAnalyzers>
-    <!--
-    TODO(cretz): Reenable when https://github.com/dotnet/format/issues/1800 fixed
     <EnforceCodeStyleInBuild>true</EnforceCodeStyleInBuild>
-    -->
+    <GenerateDocumentationFile>true</GenerateDocumentationFile>
     <ImplicitUsings>enable</ImplicitUsings>
     <Nullable>enable</Nullable>
     <PackageLicenseExpression>MIT</PackageLicenseExpression>

src/ContextPropagation/ContextPropagationInterceptor.cs

@@ -1,6 +1,7 @@
 namespace TemporalioSamples.ContextPropagation;
 
 using System.Threading.Tasks;
+using NexusRpc.Handlers;
 using Temporalio.Api.Common.V1;
 using Temporalio.Client;
 using Temporalio.Client.Interceptors;
@@ -39,6 +40,10 @@ public WorkflowInboundInterceptor InterceptWorkflow(WorkflowInboundInterceptor n
     public ActivityInboundInterceptor InterceptActivity(ActivityInboundInterceptor nextInterceptor) =>
         new ContextPropagationActivityInboundInterceptor(this, nextInterceptor);
 
+    public NexusOperationInboundInterceptor InterceptNexusOperation(
+        NexusOperationInboundInterceptor nextInterceptor) =>
+        new ContextPropagationNexusOperationInboundInterceptor(this, nextInterceptor);
+
     private Dictionary<string, Payload> HeaderFromContext(IDictionary<string, Payload>? existing)
     {
         var ret = existing != null ?
@@ -67,6 +72,28 @@ private TResult WithHeadersApplied<TResult>(
         return func();
     }
 
+    private Dictionary<string, string> HeaderFromContextForNexus(IDictionary<string, string>? existing)
+    {
+        var ret = existing != null ?
+            new Dictionary<string, string>(existing) : new Dictionary<string, string>(1);
+        // Nexus headers are string-based, so serialize context value to JSON.
+        // Alternative approach: could use payload converter and put entire payload as JSON on header.
+        ret[headerKey] = System.Text.Json.JsonSerializer.Serialize(context.Value);
+        return ret;
+    }
+
+    private Task<TResult> WithHeadersAppliedForNexusAsync<TResult>(
+        IReadOnlyDictionary<string, string>? headers, Func<Task<TResult>> func)
+    {
+        if (headers?.TryGetValue(headerKey, out var value) == true)
+        {
+            // Deserialize can return null for nullable types, which is expected
+            context.Value = System.Text.Json.JsonSerializer.Deserialize<T>(value)!;
+        }
+        // These are async local, no need to unapply afterwards
+        return func();
+    }
+
     private class ContextPropagationClientOutboundInterceptor : ClientOutboundInterceptor
     {
         private readonly ContextPropagationInterceptor<T> root;
@@ -153,6 +180,11 @@ public override Task<ChildWorkflowHandle<TWorkflow, TResult>> StartChildWorkflow
             StartChildWorkflowInput input) =>
             Next.StartChildWorkflowAsync<TWorkflow, TResult>(
                 input with { Headers = root.HeaderFromContext(input.Headers) });
+
+        public override Task<NexusOperationHandle<TResult>> StartNexusOperationAsync<TResult>(
+            StartNexusOperationInput input) =>
+            Next.StartNexusOperationAsync<TResult>(
+                input with { Headers = root.HeaderFromContextForNexus(input.Headers) });
     }
 
     private class ContextPropagationActivityInboundInterceptor : ActivityInboundInterceptor
@@ -166,4 +198,19 @@ public ContextPropagationActivityInboundInterceptor(
         public override Task<object?> ExecuteActivityAsync(ExecuteActivityInput input) =>
             root.WithHeadersApplied(input.Headers, () => Next.ExecuteActivityAsync(input));
     }
+
+    private class ContextPropagationNexusOperationInboundInterceptor : NexusOperationInboundInterceptor
+    {
+        private readonly ContextPropagationInterceptor<T> root;
+
+        public ContextPropagationNexusOperationInboundInterceptor(
+            ContextPropagationInterceptor<T> root, NexusOperationInboundInterceptor next)
+            : base(next) => this.root = root;
+
+        public override Task<OperationStartResult<object?>> ExecuteNexusOperationStartAsync(
+            ExecuteNexusOperationStartInput input) =>
+            root.WithHeadersAppliedForNexusAsync(
+                input.Context.Headers,
+                () => base.ExecuteNexusOperationStartAsync(input));
+    }
 }

src/ContextPropagation/INexusGreetingService.cs

@@ -0,0 +1,16 @@
+namespace TemporalioSamples.ContextPropagation;
+
+using NexusRpc;
+
+[NexusService]
+public interface INexusGreetingService
+{
+    static readonly string EndpointName = "context-propagation-greeting-service";
+
+    [NexusOperation]
+    GreetingOutput SayGreeting(GreetingInput input);
+
+    public record GreetingInput(string Name);
+
+    public record GreetingOutput(string Message);
+}

src/ContextPropagation/NexusGreetingHandlerWorkflow.workflow.cs

@@ -0,0 +1,27 @@
+namespace TemporalioSamples.ContextPropagation;
+
+using System.Threading.Tasks;
+using Microsoft.Extensions.Logging;
+using Temporalio.Workflows;
+
+[Workflow]
+public class NexusGreetingHandlerWorkflow
+{
+    [WorkflowQuery]
+    public string? CapturedUserId { get; private set; }
+
+    [WorkflowRun]
+    public async Task<INexusGreetingService.GreetingOutput> RunAsync(
+        INexusGreetingService.GreetingInput input)
+    {
+        // Capture context to prove propagation through Nexus to handler workflow
+        CapturedUserId = MyContext.UserId;
+        Workflow.Logger.LogInformation(
+            "Handler workflow executing for {Name}, called by user {UserId}",
+            input.Name,
+            CapturedUserId);
+
+        var message = $"Greeting for {input.Name} (processed by user: {CapturedUserId})";
+        return await Task.FromResult(new INexusGreetingService.GreetingOutput(message));
+    }
+}

src/ContextPropagation/NexusGreetingService.cs

@@ -0,0 +1,23 @@
+namespace TemporalioSamples.ContextPropagation;
+
+using Microsoft.Extensions.Logging;
+using NexusRpc.Handlers;
+using Temporalio.Nexus;
+
+[NexusServiceHandler(typeof(INexusGreetingService))]
+public class NexusGreetingService
+{
+    [NexusOperationHandler]
+    public IOperationHandler<INexusGreetingService.GreetingInput, INexusGreetingService.GreetingOutput> SayGreeting() =>
+        WorkflowRunOperationHandler.FromHandleFactory(
+            (WorkflowRunOperationContext context, INexusGreetingService.GreetingInput input) =>
+            {
+                // Log context to show it was propagated to the handler
+                NexusOperationExecutionContext.Current.Logger.LogInformation(
+                    "Nexus greeting service called by user {UserId}", MyContext.UserId);
+
+                return context.StartWorkflowAsync(
+                    (NexusGreetingHandlerWorkflow wf) => wf.RunAsync(input),
+                    new() { Id = context.HandlerContext.RequestId });
+            });
+}

src/ContextPropagation/Program.cs

@@ -40,7 +40,9 @@ async Task RunWorkerAsync()
         client,
         new TemporalWorkerOptions(taskQueue: "interceptors-sample").
             AddAllActivities<SayHelloActivities>(new()).
-            AddWorkflow<SayHelloWorkflow>());
+            AddWorkflow<SayHelloWorkflow>().
+            AddNexusService(new NexusGreetingService()).
+            AddWorkflow<NexusGreetingHandlerWorkflow>());
     try
     {
         await worker.ExecuteAsync(tokenSource.Token);

src/ContextPropagation/README.md

@@ -1,8 +1,8 @@
 # Interceptors
 
-This sample demonstrates how to use interceptors to propagate contextual information from an `AsyncLocal` throughout the
-workflows and activities. While this demonstrates context propagation specifically, it can also be used to show how to
-create interceptors for any other purpose.
+This sample demonstrates how to use interceptors to propagate contextual information from an `AsyncLocal` throughout
+workflows, activities, and Nexus operations. While this demonstrates context propagation specifically, it can also be
+used to show how to create interceptors for any other purpose.
 
 To run, first see [README.md](../../README.md) for prerequisites. Then, run the following from this directory in a
 separate terminal to start the worker:
@@ -14,4 +14,4 @@ Then in another terminal, run the workflow from this directory:
     dotnet run workflow
 
 The workflow terminal will show the completed workflow result and the worker terminal will show the contextual user ID
-is present in the workflow and activity.
+is present in the workflow, Nexus operation handler, Nexus handler workflow, and activity.

src/ContextPropagation/SayHelloWorkflow.workflow.cs

@@ -13,8 +13,16 @@ public async Task<string> RunAsync(string name)
     {
         Workflow.Logger.LogInformation("Workflow called by user {UserId}", MyContext.UserId);
 
-        // Wait for signal then run activity
+        // Wait for signal then call Nexus service and run activity
         await Workflow.WaitConditionAsync(() => complete);
+
+        // Call Nexus service to demonstrate context propagation through Nexus
+        var nexusClient = Workflow.CreateNexusClient<INexusGreetingService>(
+            INexusGreetingService.EndpointName);
+        var nexusResult = await nexusClient.ExecuteNexusOperationAsync(
+            svc => svc.SayGreeting(new(name)));
+        Workflow.Logger.LogInformation("Nexus result: {Result}", nexusResult.Message);
+
         return await Workflow.ExecuteActivityAsync(
             (SayHelloActivities act) => act.SayHello(name),
             new() { StartToCloseTimeout = TimeSpan.FromMinutes(5) });