Use object to not couple to Json and allow output formatters

docs/scatter-gather.md

@@ -12,7 +12,7 @@ public void Configure(IApplicationBuilder app, ILoggerFactory loggerFactory)
     app.UseRouting();
     app.UseEndpoints(builder => builder.MapScatterGather(template: "api/scatter-gather", new ScatterGatherOptions()
     {
-        Gatherers = new List<Gatherer>
+        Gatherers = new List<IGatherer>
         {
             new HttpGatherer(key: "ASamplesSource", destinationUrl: "https://a.web.server/api/samples/ASamplesSource"),
             new HttpGatherer(key: "AnotherSamplesSource", destinationUrl: "https://another.web.server/api/samples/AnotherSamplesSource")
@@ -38,7 +38,7 @@ public void Configure(IApplicationBuilder app, ILoggerFactory loggerFactory)
 {
     app.UseEndpoints(builder => builder.MapScatterGather(template: "api/scatter-gather", new ScatterGatherOptions()
     {
-        Gatherers = new List<Gatherer>
+        Gatherers = new List<IGatherer>
         {
             new HttpGatherer("ASamplesSource", "https://a.web.server/api/samples/ASamplesSource")
             {
@@ -78,7 +78,7 @@ public class CustomHttpGatherer : HttpGatherer
     }
 }
 ```
-<sup><a href='/src/Snippets/ScatterGather/TransformResponse.cs#L12-L24' title='Snippet source file'>snippet source</a> | <a href='#snippet-scatter-gather-transform-response' title='Start of snippet'>anchor</a></sup>
+<sup><a href='/src/Snippets/ScatterGather/TransformResponse.cs#L13-L25' title='Snippet source file'>snippet source</a> | <a href='#snippet-scatter-gather-transform-response' title='Start of snippet'>anchor</a></sup>
 <!-- endSnippet -->
 
 ### Taking control of the downstream invocation process
@@ -94,11 +94,10 @@ public class CustomHttpGatherer : HttpGatherer
 
     public override Task<IEnumerable<JsonNode>> Gather(HttpContext context)
     {
-        // by overriding this method we can implement custom logic
-        // to gather the responses from the downstream service.
+
         return base.Gather(context);
     }
 }
 ```
-<sup><a href='/src/Snippets/ScatterGather/GatherMethodOverride.cs#L12-L24' title='Snippet source file'>snippet source</a> | <a href='#snippet-scatter-gather-gather-override' title='Start of snippet'>anchor</a></sup>
+<sup><a href='/src/Snippets/ScatterGather/GatherMethodOverride.cs#L12-L23' title='Snippet source file'>snippet source</a> | <a href='#snippet-scatter-gather-gather-override' title='Start of snippet'>anchor</a></sup>
 <!-- endSnippet -->

src/ServiceComposer.AspNetCore.Tests/API/APIApprovals.Approve_API.verified.txt

@@ -60,13 +60,14 @@ namespace ServiceComposer.AspNetCore
         " removed in v3. Use attribute routing based composition, and CompositionEventHan" +
         "dler<TEvent>.", true)]
     public delegate System.Threading.Tasks.Task EventHandler<TEvent>(string requestId, [System.Runtime.CompilerServices.Dynamic] object viewModel, TEvent @event, Microsoft.AspNetCore.Routing.RouteData routeData, Microsoft.AspNetCore.Http.HttpRequest httpRequest);
-    public abstract class Gatherer
+    public abstract class Gatherer<T> : ServiceComposer.AspNetCore.IGatherer
+        where T :  class
     {
         protected Gatherer(string key) { }
         public string Key { get; }
-        public abstract System.Threading.Tasks.Task<System.Collections.Generic.IEnumerable<System.Text.Json.Nodes.JsonNode>> Gather(Microsoft.AspNetCore.Http.HttpContext context);
+        public abstract System.Threading.Tasks.Task<System.Collections.Generic.IEnumerable<T>> Gather(Microsoft.AspNetCore.Http.HttpContext context);
     }
-    public class HttpGatherer : ServiceComposer.AspNetCore.Gatherer
+    public class HttpGatherer : ServiceComposer.AspNetCore.Gatherer<System.Text.Json.Nodes.JsonNode>
     {
         public HttpGatherer(string key, string destinationUrl) { }
         public System.Func<Microsoft.AspNetCore.Http.HttpRequest, string, string> DefaultDestinationUrlMapper { get; }
@@ -92,8 +93,8 @@ namespace ServiceComposer.AspNetCore
     }
     public interface IAggregator
     {
-        void Add(System.Collections.Generic.IEnumerable<System.Text.Json.Nodes.JsonNode> nodes);
-        System.Threading.Tasks.Task<System.Text.Json.Nodes.JsonArray> Aggregate();
+        void Add(System.Collections.Generic.IEnumerable<object> nodes);
+        System.Threading.Tasks.Task<object> Aggregate();
     }
     public interface ICompositionContext
     {
@@ -117,6 +118,11 @@ namespace ServiceComposer.AspNetCore
         System.Threading.Tasks.Task Handle(Microsoft.AspNetCore.Http.HttpRequest request);
     }
     public interface IEndpointScopedViewModelFactory : ServiceComposer.AspNetCore.IViewModelFactory { }
+    public interface IGatherer
+    {
+        string Key { get; }
+        System.Threading.Tasks.Task<System.Collections.Generic.IEnumerable<object>> Gather(Microsoft.AspNetCore.Http.HttpContext context);
+    }
     [System.Obsolete("IHandleRequests is obsoleted and will be treated as an error starting v2 and remo" +
         "ved in v3. Use attribute routing based composition and ICompositionRequestsHandl" +
         "er.", true)]
@@ -188,7 +194,7 @@ namespace ServiceComposer.AspNetCore
     {
         public ScatterGatherOptions() { }
         public System.Type CustomAggregator { get; set; }
-        public System.Collections.Generic.IList<ServiceComposer.AspNetCore.Gatherer> Gatherers { get; set; }
+        public System.Collections.Generic.IList<ServiceComposer.AspNetCore.IGatherer> Gatherers { get; set; }
     }
     public static class ServiceCollectionExtensions
     {

src/ServiceComposer.AspNetCore.Tests/ScatterGather/Get_with_2_gatherers.cs

@@ -73,6 +73,7 @@ HttpClient ClientProvider(string name) =>
                 // TODO: does this need to register a default HTTP client?
                 // services.AddScatterGather();
                 services.AddRouting();
+                services.AddControllers();
                 services.Replace(
                     new ServiceDescriptor(typeof(IHttpClientFactory), 
                     new DelegateHttpClientFactory(ClientProvider)));
@@ -84,7 +85,7 @@ HttpClient ClientProvider(string name) =>
                 {
                     builder.MapScatterGather(template: "/samples", new ScatterGatherOptions
                     {
-                        Gatherers = new List<Gatherer>
+                        Gatherers = new List<IGatherer>
                         {
                             new HttpGatherer(key: "ASamplesSource", destinationUrl: "/samples/ASamplesSource"),
                             new HttpGatherer(key: "AnotherSamplesSource", destinationUrl: "/samples/AnotherSamplesSource")

src/ServiceComposer.AspNetCore.Tests/ScatterGather/Get_with_HttpGatherer_and_CustomGatherer.cs

@@ -0,0 +1,113 @@
+using System;
+using System.Threading.Tasks;
+using Microsoft.AspNetCore.Builder;
+using Microsoft.Extensions.DependencyInjection;
+using ServiceComposer.AspNetCore.Testing;
+using Xunit;
+using System.Collections.Generic;
+using System.Linq;
+using System.Net.Http;
+using System.Text.Json;
+using System.Text.Json.Nodes;
+using Microsoft.AspNetCore.Http;
+using Microsoft.Extensions.DependencyInjection.Extensions;
+using ServiceComposer.AspNetCore.Tests.Utils;
+
+namespace ServiceComposer.AspNetCore.Tests.ScatterGather;
+
+public class Get_with_HttpGatherer_and_CustomGatherer
+{
+    class CustomGatherer : IGatherer
+    {
+        public string Key { get; } = "CustomGatherer";
+        public Task<IEnumerable<object>> Gather(HttpContext context)
+        {
+            var data = (IEnumerable<object>)(new []{ new { Value = "ACustomSample" } });
+            return Task.FromResult(data);
+        }
+    }
+
+    [Fact]
+    public async Task Returns_expected_response()
+    {
+        // Arrange
+        var aSampleSourceClient = new SelfContainedWebApplicationFactoryWithWebHost<Dummy>
+        (
+            configureServices: services =>
+            {
+                services.AddRouting();
+            },
+            configure: app =>
+            {
+                app.UseRouting();
+                app.UseEndpoints(builder =>
+                {
+                    builder.MapGet("/samples/ASamplesSource", () =>
+                    {
+                        return new []{ new { Value = "ASample" } };
+                    });
+                });
+            }
+        ).CreateClient();
+
+        var client = new SelfContainedWebApplicationFactoryWithWebHost<Dummy>
+        (
+            configureServices: services =>
+            {
+                HttpClient ClientProvider(string name) =>
+                    name switch
+                    {
+                        "ASamplesSource" => aSampleSourceClient,
+                        _ => throw new NotSupportedException($"Missing HTTP client for {name}")
+                    };
+
+                // TODO: does this need to register a default HTTP client?
+                // services.AddScatterGather();
+                services.AddRouting();
+                services.AddControllers();
+                services.Replace(
+                    new ServiceDescriptor(typeof(IHttpClientFactory), 
+                    new DelegateHttpClientFactory(ClientProvider)));
+            },
+            configure: app =>
+            {
+                app.UseRouting();
+                app.UseEndpoints(builder =>
+                {
+                    builder.MapScatterGather(template: "/samples", new ScatterGatherOptions
+                    {
+                        Gatherers = new List<IGatherer>
+                        {
+                            new HttpGatherer(key: "ASamplesSource", destinationUrl: "/samples/ASamplesSource"),
+                            new CustomGatherer()
+                        }
+                    });
+                });
+            }
+        ).CreateClient();
+
+        // Act
+        var response = await client.GetAsync("/samples");
+
+        // Assert
+        Assert.True(response.IsSuccessStatusCode);
+
+        var responseString = await response.Content.ReadAsStringAsync();
+        var responseArray = JsonNode.Parse(responseString)!.AsArray();
+        var responseArrayAsJsonStrings = new HashSet<string>(responseArray.Select(n=>n.ToJsonString()));
+
+        var expectedArray = JsonNode.Parse(JsonSerializer.Serialize( new[]
+        {
+            new {Value = "ASample"},
+            new {Value = "ACustomSample"}
+        }, new JsonSerializerOptions
+        {
+            PropertyNamingPolicy = JsonNamingPolicy.CamelCase
+        }))!.AsArray();
+        var expectedArrayAsJsonStrings = new HashSet<string>(expectedArray.Select(n=>n.ToJsonString()));
+
+        Assert.Equal(2, responseArray.Count);
+        Assert.Equivalent(expectedArrayAsJsonStrings, responseArrayAsJsonStrings);
+    }
+}
+

src/ServiceComposer.AspNetCore.Tests/ScatterGather/When_using_query_string.cs

@@ -84,7 +84,7 @@ HttpClient ClientProvider(string name) =>
                 {
                     builder.MapScatterGather(template: "/samples", new ScatterGatherOptions
                     {
-                        Gatherers = new List<Gatherer>
+                        Gatherers = new List<IGatherer>
                         {
                             new HttpGatherer(key: "ASamplesSource", destinationUrl: "/samples/ASamplesSource"),
                             new HttpGatherer(key: "AnotherSamplesSource", destinationUrl: "/samples/AnotherSamplesSource")

src/ServiceComposer.AspNetCore/ScatterGather/DefaultAggregator.cs

@@ -9,17 +9,17 @@ class DefaultAggregator : IAggregator
 {
     readonly ConcurrentBag<JsonNode> allNodes = new();
 
-    public void Add(IEnumerable<JsonNode> nodes)
+    public void Add(IEnumerable<object> nodes)
     {
         foreach (var node in nodes)
         {
-            allNodes.Add(node);
+            allNodes.Add((JsonNode)node);
         }
     }
 
-    public Task<JsonArray> Aggregate()
+    public Task<object> Aggregate()
     {
         var responsesArray = new JsonArray(allNodes.ToArray());
-        return Task.FromResult(responsesArray);
+        return Task.FromResult((object)responsesArray);
     }
 }

src/ServiceComposer.AspNetCore/ScatterGather/Gatherer.cs

@@ -1,11 +1,10 @@
 using System.Collections.Generic;
-using System.Text.Json.Nodes;
 using System.Threading.Tasks;
 using Microsoft.AspNetCore.Http;
 
 namespace ServiceComposer.AspNetCore;
 
-public abstract class Gatherer
+public abstract class Gatherer<T> : IGatherer where T : class
 {
     protected Gatherer(string key)
     {
@@ -14,6 +13,10 @@ protected Gatherer(string key)
 
     public string Key { get; }
 
-    // TODO: how to use generics to remove the dependency on JSON?
-    public abstract Task<IEnumerable<JsonNode>> Gather(HttpContext context);
+    Task<IEnumerable<object>> IGatherer.Gather(HttpContext context)
+    {
+        return Gather(context).ContinueWith(t => (IEnumerable<object>)t.Result);
+    }
+
+    public abstract Task<IEnumerable<T>> Gather(HttpContext context);
 }

src/ServiceComposer.AspNetCore/ScatterGather/HttpGatherer.cs

@@ -8,7 +8,7 @@
 
 namespace ServiceComposer.AspNetCore;
 
-public class HttpGatherer : Gatherer
+public class HttpGatherer : Gatherer<JsonNode>
 {
     public HttpGatherer(string key, string destinationUrl)
         : base(key)

src/ServiceComposer.AspNetCore/ScatterGather/IAggregator.cs

@@ -6,6 +6,6 @@ namespace ServiceComposer.AspNetCore;
 
 public interface IAggregator
 {
-    void Add(IEnumerable<JsonNode> nodes);
-    Task<JsonArray> Aggregate();
+    void Add(IEnumerable<object> nodes);
+    Task<object> Aggregate();
 }

src/ServiceComposer.AspNetCore/ScatterGather/IGatherer.cs

@@ -0,0 +1,11 @@
+using System.Collections.Generic;
+using System.Threading.Tasks;
+using Microsoft.AspNetCore.Http;
+
+namespace ServiceComposer.AspNetCore;
+
+public interface IGatherer
+{
+    string Key { get; }
+    Task<IEnumerable<object>> Gather(HttpContext context);
+}

src/ServiceComposer.AspNetCore/ScatterGather/ScatterGatherEndpointBuilderExtensions.cs

@@ -31,9 +31,8 @@ public static IEndpointConventionBuilder MapScatterGather(this IEndpointRouteBui
             await Task.WhenAll(tasks);
             var responses = await aggregator.Aggregate();
 
-            // TODO: support output formatters by using the WriteModelAsync extension method.
-            // It must be under a setting flag, because it requires a dependency on MVC.
-            await context.Response.WriteAsync(responses.ToJsonString());
+            // TODO: support output formatters by using the WriteModelAsync extension method. It must be under a setting flag, because it requires a dependency on MVC.
+            await context.Response.WriteAsync( System.Text.Json.JsonSerializer.Serialize(responses));
         });
     }
 }

src/ServiceComposer.AspNetCore/ScatterGather/ScatterGatherOptions.cs

@@ -14,8 +14,9 @@ internal IAggregator GetAggregator(HttpContext httpContext)
         {
             return (IAggregator)httpContext.RequestServices.GetRequiredService(CustomAggregator);
         }
+
         return new DefaultAggregator();
     }
 
-    public IList<Gatherer> Gatherers { get; set; }
+    public IList<IGatherer> Gatherers { get; set; }
 }

src/Snippets/ScatterGather/CustomizingDownstreamURLs.cs

@@ -12,7 +12,7 @@ public void Configure(IApplicationBuilder app, ILoggerFactory loggerFactory)
     {
         app.UseEndpoints(builder => builder.MapScatterGather(template: "api/scatter-gather", new ScatterGatherOptions()
         {
-            Gatherers = new List<Gatherer>
+            Gatherers = new List<IGatherer>
             {
                 new HttpGatherer("ASamplesSource", "https://a.web.server/api/samples/ASamplesSource")
                 {

src/Snippets/ScatterGather/GatherMethodOverride.cs

@@ -16,8 +16,7 @@ public CustomHttpGatherer(string key, string destination) : base(key, destinatio
 
         public override Task<IEnumerable<JsonNode>> Gather(HttpContext context)
         {
-            // by overriding this method we can implement custom logic
-            // to gather the responses from the downstream service.
+
             return base.Gather(context);
         }
     }

src/Snippets/ScatterGather/Startup.cs

@@ -14,7 +14,7 @@ public void Configure(IApplicationBuilder app, ILoggerFactory loggerFactory)
         app.UseRouting();
         app.UseEndpoints(builder => builder.MapScatterGather(template: "api/scatter-gather", new ScatterGatherOptions()
         {
-            Gatherers = new List<Gatherer>
+            Gatherers = new List<IGatherer>
             {
                 new HttpGatherer(key: "ASamplesSource", destinationUrl: "https://a.web.server/api/samples/ASamplesSource"),
                 new HttpGatherer(key: "AnotherSamplesSource", destinationUrl: "https://another.web.server/api/samples/AnotherSamplesSource")

src/Snippets/ScatterGather/TransformResponse.cs

@@ -3,6 +3,7 @@
 using System.Net.Http;
 using System.Text.Json.Nodes;
 using System.Threading.Tasks;
+using Microsoft.AspNetCore.Http;
 using ServiceComposer.AspNetCore;
 
 namespace Snippets.ScatterGather;