Allow for nulls to be stripped from the result. (#5627)

src/HotChocolate/AspNetCore/src/AspNetCore/Extensions/HotChocolateAspNetCoreServiceCollectionExtensions.Http.cs

@@ -3,6 +3,7 @@
 using HotChocolate.AspNetCore;
 using HotChocolate.AspNetCore.Serialization;
 using HotChocolate.Execution.Configuration;
+using HotChocolate.Execution.Serialization;
 using HotChocolate.Utilities;
 
 // ReSharper disable once CheckNamespace
@@ -105,6 +106,28 @@ public static IServiceCollection AddHttpResponseFormatter(
         return services;
     }
 
+    /// <summary>
+    /// Adds the <see cref="DefaultHttpResponseFormatter"/> with specific formatter options
+    /// to the DI.
+    /// </summary>
+    /// <param name="services">
+    /// The <see cref="IServiceCollection"/>.
+    /// </param>
+    /// <param name="options">
+    /// The JSON result formatter options
+    /// </param>
+    /// <returns>
+    /// Returns the <see cref="IServiceCollection"/> so that configuration can be chained.
+    /// </returns>
+    public static IServiceCollection AddHttpResponseFormatter(
+        this IServiceCollection services,
+        JsonResultFormatterOptions options)
+    {
+        services.RemoveAll<IHttpResponseFormatter>();
+        services.AddSingleton<IHttpResponseFormatter>(new DefaultHttpResponseFormatter(options));
+        return services;
+    }
+
     /// <summary>
     /// Adds a custom HTTP response formatter to the DI.
     /// </summary>
@@ -125,4 +148,29 @@ public static IServiceCollection AddHttpResponseFormatter<T>(
         services.AddSingleton<IHttpResponseFormatter, T>();
         return services;
     }
+
+    /// <summary>
+    /// Adds a custom HTTP response formatter to the DI.
+    /// </summary>
+    /// <param name="services">
+    /// The <see cref="IServiceCollection"/>.
+    /// </param>
+    /// <param name="factory">
+    /// The service factory.
+    /// </param>
+    /// <typeparam name="T">
+    /// The type of the custom <see cref="IHttpResponseFormatter"/>.
+    /// </typeparam>
+    /// <returns>
+    /// Returns the <see cref="IServiceCollection"/> so that configuration can be chained.
+    /// </returns>
+    public static IServiceCollection AddHttpResponseFormatter<T>(
+        this IServiceCollection services,
+        Func<IServiceProvider, T> factory)
+        where T : class, IHttpResponseFormatter
+    {
+        services.RemoveAll<IHttpResponseFormatter>();
+        services.AddSingleton<IHttpResponseFormatter>(factory);
+        return services;
+    }
 }

src/HotChocolate/AspNetCore/src/AspNetCore/Serialization/DefaultHttpResponseFormatter.cs

@@ -37,10 +37,21 @@ public class DefaultHttpResponseFormatter : IHttpResponseFormatter
     public DefaultHttpResponseFormatter(
         bool indented = false,
         JavaScriptEncoder? encoder = null)
+        : this(new JsonResultFormatterOptions { Indented = indented, Encoder = encoder })
     {
-        _jsonFormatter = new JsonResultFormatter(indented, encoder);
+    }
+
+    /// <summary>
+    /// Creates a new instance of <see cref="DefaultHttpResponseFormatter" />.
+    /// </summary>
+    /// <param name="options">
+    /// The JSON result formatter options
+    /// </param>
+    public DefaultHttpResponseFormatter(JsonResultFormatterOptions options)
+    {
+        _jsonFormatter = new JsonResultFormatter(options);
         _multiPartFormatter = new MultiPartResultFormatter(_jsonFormatter);
-        _eventStreamResultFormatter = new EventStreamResultFormatter(indented, encoder);
+        _eventStreamResultFormatter = new EventStreamResultFormatter(options);
     }
 
     public GraphQLRequestFlags CreateRequestFlags(

src/HotChocolate/AspNetCore/test/AspNetCore.Tests.Utilities/ServerTestBase.cs

@@ -97,6 +97,7 @@ protected virtual TestServer CreateStarWarsServer(
                         endpoints.MapGraphQL("/arguments", "arguments");
                         endpoints.MapGraphQL("/upload", "upload");
                         endpoints.MapGraphQL("/starwars", "StarWars");
+                        endpoints.MapGraphQL("/test", "test");
                     }));
     }
 

src/HotChocolate/AspNetCore/test/AspNetCore.Tests/HttpPostMiddlewareTests.cs

@@ -1,17 +1,23 @@
 using System.Net;
+using System.Net.Http.Json;
 using CookieCrumble;
 using Microsoft.AspNetCore.Builder;
 using Microsoft.AspNetCore.Http;
 using Microsoft.Extensions.DependencyInjection;
 using HotChocolate.AspNetCore.Instrumentation;
+using HotChocolate.AspNetCore.Serialization;
 using HotChocolate.AspNetCore.Tests.Utilities;
 using HotChocolate.Execution;
+using HotChocolate.Execution.Serialization;
 using Newtonsoft.Json;
+using static HotChocolate.Execution.Serialization.JsonNullIgnoreCondition;
 
 namespace HotChocolate.AspNetCore;
 
 public class HttpPostMiddlewareTests : ServerTestBase
 {
+    private static readonly Uri _url = new("http://localhost:5000/graphql");
+
     public HttpPostMiddlewareTests(TestServerFactory serverFactory)
         : base(serverFactory)
     {
@@ -1141,6 +1147,122 @@ await server.PostAsync(new ClientQueryRequest
         result.MatchSnapshot();
     }
 
+    [Fact]
+    public async Task Strip_Null_Values_Variant_1()
+    {
+        // arrange
+        var server = CreateStarWarsServer(
+            configureServices: s => s.AddHttpResponseFormatter(
+                _ => new DefaultHttpResponseFormatter(new() { NullIgnoreCondition = Fields })));
+        var client = server.CreateClient();
+
+        // act
+        using var request = new HttpRequestMessage(HttpMethod.Post, _url)
+        {
+            Content = JsonContent.Create(
+                new ClientQueryRequest
+                {
+                    Query = "{ __schema { description } }"
+                })
+        };
+
+        using var response = await client.SendAsync(request);
+
+        // assert
+        // expected response content-type: application/json
+        // expected status code: 200
+        Snapshot
+            .Create()
+            .Add(response)
+            .MatchInline(
+                @"Headers:
+                Content-Type: application/graphql-response+json; charset=utf-8
+                -------------------------->
+                Status Code: OK
+                -------------------------->
+                {""data"":{""__schema"":{}}}");
+    }
+
+    [Fact]
+    public async Task Strip_Null_Values_Variant_2()
+    {
+        // arrange
+        var server = CreateStarWarsServer(
+            configureServices: s => s.AddHttpResponseFormatter(
+                new JsonResultFormatterOptions { NullIgnoreCondition = Fields }));
+        var client = server.CreateClient();
+
+        // act
+        using var request = new HttpRequestMessage(HttpMethod.Post, _url)
+        {
+            Content = JsonContent.Create(
+                new ClientQueryRequest
+                {
+                    Query = "{ __schema { description } }"
+                })
+        };
+
+        using var response = await client.SendAsync(request);
+
+        // assert
+        // expected response content-type: application/json
+        // expected status code: 200
+        Snapshot
+            .Create()
+            .Add(response)
+            .MatchInline(
+                @"Headers:
+                Content-Type: application/graphql-response+json; charset=utf-8
+                -------------------------->
+                Status Code: OK
+                -------------------------->
+                {""data"":{""__schema"":{}}}");
+    }
+
+    [Fact]
+    public async Task Strip_Null_Elements()
+    {
+        // arrange
+        var url = new Uri("http://localhost:5000/test");
+
+        var server = CreateStarWarsServer(
+            configureServices: s => s
+                .AddGraphQLServer("test")
+                .AddQueryType<NullListQuery>()
+                .Services
+                .AddHttpResponseFormatter(new JsonResultFormatterOptions
+                {
+                    NullIgnoreCondition = Lists
+                }));
+        var client = server.CreateClient();
+
+        // act
+        using var request = new HttpRequestMessage(HttpMethod.Post, url)
+        {
+            Content = JsonContent.Create(
+                new ClientQueryRequest
+                {
+                    Query = "{ nullValues }"
+                })
+        };
+
+        using var response = await client.SendAsync(request);
+
+        // assert
+        // expected response content-type: application/json
+        // expected status code: 200
+        Snapshot
+            .Create()
+            .Add(response)
+            .MatchInline(
+                @"Headers:
+                Content-Type: application/graphql-response+json; charset=utf-8
+                -------------------------->
+                Status Code: OK
+                -------------------------->
+                {""data"":{""nullValues"":[""abc""]}}");
+    }
+
     public class ErrorRequestInterceptor : DefaultHttpRequestInterceptor
     {
         public override ValueTask OnCreateAsync(
@@ -1163,4 +1285,9 @@ public override IDisposable ExecuteHttpRequest(HttpContext context, HttpRequestK
             return EmptyScope;
         }
     }
+
+    public class NullListQuery
+    {
+        public List<string?> NullValues => new() { null, "abc", null };
+    }
 }

src/HotChocolate/Core/src/Execution/Extensions/ExecutionResultExtensions.cs

@@ -9,8 +9,8 @@ namespace HotChocolate;
 
 public static class ExecutionResultExtensions
 {
-    private static readonly JsonResultFormatter _formatter = new(false);
-    private static readonly JsonResultFormatter _formatterIndented = new(true);
+    private static readonly JsonResultFormatter _formatter = new(new() { Indented = false});
+    private static readonly JsonResultFormatter _formatterIndented = new(new() { Indented = true});
 
     public static void WriteTo(
         this IQueryResult result,

src/HotChocolate/Core/src/Execution/Serialization/EventStreamResultFormatter.cs

@@ -35,22 +35,13 @@ private static readonly byte[] _completeEvent
     /// <summary>
     /// Creates a new instance of <see cref="EventStreamResultFormatter" />.
     /// </summary>
-    /// <param name="indented">
-    /// Defines whether the underlying <see cref="Utf8JsonWriter"/>
-    /// should pretty print the JSON which includes:
-    /// indenting nested JSON tokens, adding new lines, and adding
-    /// white space between property names and values.
-    /// By default, the JSON is written without any extra white space.
+    /// <param name="options">
+    /// The JSON result formatter options
     /// </param>
-    /// <param name="encoder">
-    /// Gets or sets the encoder to use when escaping strings, or null to use the default encoder.
-    /// </param>
-    public EventStreamResultFormatter(
-        bool indented = false,
-        JavaScriptEncoder? encoder = null)
+    public EventStreamResultFormatter(JsonResultFormatterOptions options)
     {
-        _options = new JsonWriterOptions { Indented = indented, Encoder = encoder };
-        _payloadFormatter = new JsonResultFormatter(indented, encoder);
+        _options = options.CreateWriterOptions();
+        _payloadFormatter = new JsonResultFormatter(options);
     }
 
     /// <inheritdoc cref="IExecutionResultFormatter.FormatAsync(IExecutionResult, Stream, CancellationToken)" />

src/HotChocolate/Core/src/Execution/Serialization/JsonNullIgnoreCondition.cs

@@ -0,0 +1,27 @@
+namespace HotChocolate.Execution.Serialization;
+
+/// <summary>
+/// Specifies when null values are ignored.
+/// </summary>
+public enum JsonNullIgnoreCondition
+{
+    /// <summary>
+    /// No null values are ignore.
+    /// </summary>
+    Default = 0,
+
+    /// <summary>
+    /// Fields that have a null value are ignored.
+    /// </summary>
+    Fields = 1,
+
+    /// <summary>
+    /// Null elements in lists are ignored.
+    /// </summary>
+    Lists = 2,
+
+    /// <summary>
+    /// Fields that have a null value and null elements in lists are ignored.
+    /// </summary>
+    All = 4
+}