Add support for Mutations to Fusion.

src/HotChocolate/AspNetCore/test/Transport.Sockets.Client.Tests/GraphQLOverWebSocket/WebSocketClientProtocolTests.cs

@@ -1,3 +1,4 @@
+using System.Text.Json;
 using CookieCrumble;
 using HotChocolate.AspNetCore;
 using HotChocolate.AspNetCore.Subscriptions;
@@ -174,9 +175,9 @@ public Task Send_Subscribe_ValidationError()
             // assert
             await foreach (var result in socketResult.ReadResultsAsync().WithCancellation(ct))
             {
-                Assert.Null(result.Data);
-                Assert.NotNull(result.Errors);
-                Assert.Null(result.Extensions);
+                Assert.Equal(JsonValueKind.Undefined, result.Data.ValueKind);
+                Assert.Equal(JsonValueKind.Array, result.Errors.ValueKind);
+                Assert.Equal(JsonValueKind.Undefined, result.Extensions.ValueKind);
                 snapshot.Add(result.Errors);
             }
 

src/HotChocolate/Data/test/Data.Projections.SqlServer.Tests/__snapshots__/QueryableFirstOrDefaultTests.Create_DeepFilterObjectTwoProjections_Executable_NET6_0.snap

@@ -0,0 +1,27 @@
+Result:
+---------------
+{
+  "errors": [
+    {
+      "message": "Unexpected Execution Error",
+      "locations": [
+        {
+          "line": 2,
+          "column": 25
+        }
+      ],
+      "path": [
+        "rootExecutable"
+      ]
+    }
+  ],
+  "data": {
+    "rootExecutable": null
+  }
+}
+---------------
+
+SQL:
+---------------
+Microsoft.EntityFrameworkCore.Query.Internal.EntityQueryable`1[HotChocolate.Data.Projections.QueryableFirstOrDefaultTests+Bar]
+---------------

src/HotChocolate/Data/test/Data.Projections.SqlServer.Tests/__snapshots__/QueryableFirstOrDefaultTests.Create_DeepFilterObjectTwoProjections_Executable_NET7_0.snap

@@ -0,0 +1,27 @@
+Result:
+---------------
+{
+  "errors": [
+    {
+      "message": "Unexpected Execution Error",
+      "locations": [
+        {
+          "line": 2,
+          "column": 25
+        }
+      ],
+      "path": [
+        "rootExecutable"
+      ]
+    }
+  ],
+  "data": {
+    "rootExecutable": null
+  }
+}
+---------------
+
+SQL:
+---------------
+Microsoft.EntityFrameworkCore.Query.Internal.EntityQueryable`1[HotChocolate.Data.Projections.QueryableFirstOrDefaultTests+Bar]
+---------------

src/HotChocolate/Fusion/src/Composition/FusionGraphComposer.cs

@@ -53,7 +53,7 @@ internal FusionGraphComposer(
                 .Use<PrepareFusionSchemaMiddleware>()
                 .Use<MergeEntityMiddleware>()
                 .Use(() => new MergeTypeMiddleware(mergeHandlers))
-                .Use<MergeQueryTypeMiddleware>()
+                .Use<MergeQueryAndMutationTypeMiddleware>()
                 .Use<MergeSubscriptionTypeMiddleware>()
                 .Use<RemoveFusionTypesMiddleware>()
                 .Build();

src/HotChocolate/Fusion/src/Composition/Pipeline/MergeQueryTypeMiddleware.cs → src/HotChocolate/Fusion/src/Composition/Pipeline/MergeQueryAndMutationTypeMiddleware.cs

@@ -3,7 +3,7 @@
 
 namespace HotChocolate.Fusion.Composition.Pipeline;
 
-internal sealed class MergeQueryTypeMiddleware : IMergeMiddleware
+internal sealed class MergeQueryAndMutationTypeMiddleware : IMergeMiddleware
 {
     public async ValueTask InvokeAsync(CompositionContext context, MergeDelegate next)
     {
@@ -19,39 +19,20 @@ public async ValueTask InvokeAsync(CompositionContext context, MergeDelegate nex
                     context.FusionGraph.Types.Add(queryType);
                 }
 
-                foreach (var field in schema.QueryType.Fields)
+                MergeRootFields(context, schema, schema.QueryType, queryType);
+            }
+
+            if (schema.MutationType is not null)
+            {
+                var queryType = context.FusionGraph.MutationType!;
+
+                if (context.FusionGraph.MutationType is null)
                 {
-                    if (queryType.Fields.TryGetField(field.Name, out var targetField))
-                    {
-                        context.MergeField(field, targetField, queryType.Name);
-                    }
-                    else
-                    {
-                        targetField = context.CreateField(field, context.FusionGraph);
-                        queryType.Fields.Add(targetField);
-                    }
-
-                    var arguments = new List<ArgumentNode>();
-
-                    var selection = new FieldNode(
-                        null,
-                        new NameNode(field.GetOriginalName()),
-                        null,
-                        null,
-                        Array.Empty<DirectiveNode>(),
-                        arguments,
-                        null);
-
-                    var selectionSet = new SelectionSetNode(new[] { selection });
-
-                    foreach (var arg in field.Arguments)
-                    {
-                        arguments.Add(new ArgumentNode(arg.Name, new VariableNode(arg.Name)));
-                        context.ApplyVariable(targetField, arg, schema.Name);
-                    }
-
-                    context.ApplyResolvers(targetField, selectionSet, schema.Name);
+                    queryType = context.FusionGraph.MutationType = new ObjectType("Mutation");
+                    context.FusionGraph.Types.Add(queryType);
                 }
+
+                MergeRootFields(context, schema, schema.MutationType, queryType);
             }
         }
 
@@ -60,6 +41,47 @@ public async ValueTask InvokeAsync(CompositionContext context, MergeDelegate nex
             await next(context).ConfigureAwait(false);
         }
     }
+
+    private static void MergeRootFields(
+        CompositionContext context,
+        Schema sourceSchema,
+        ObjectType sourceRootType,
+        ObjectType targetRootType)
+    {
+        foreach (var field in sourceRootType.Fields)
+        {
+            if (targetRootType.Fields.TryGetField(field.Name, out var targetField))
+            {
+                context.MergeField(field, targetField, targetRootType.Name);
+            }
+            else
+            {
+                targetField = context.CreateField(field, context.FusionGraph);
+                targetRootType.Fields.Add(targetField);
+            }
+
+            var arguments = new List<ArgumentNode>();
+
+            var selection = new FieldNode(
+                null,
+                new NameNode(field.GetOriginalName()),
+                null,
+                null,
+                Array.Empty<DirectiveNode>(),
+                arguments,
+                null);
+
+            var selectionSet = new SelectionSetNode(new[] { selection });
+
+            foreach (var arg in field.Arguments)
+            {
+                arguments.Add(new ArgumentNode(arg.Name, new VariableNode(arg.Name)));
+                context.ApplyVariable(targetField, arg, sourceSchema.Name);
+            }
+
+            context.ApplyResolvers(targetField, selectionSet, sourceSchema.Name);
+        }
+    }
 }
 
 static file class MergeQueryTypeMiddlewareExtensions

src/HotChocolate/Fusion/src/Core/FusionResources.resx

@@ -48,4 +48,7 @@
   <data name="FusionRequestExecutorBuilderExtensions_AddFusionGatewayServer_NoSchema" xml:space="preserve">
     <value>A valid service configuration must always produce a schema document.</value>
   </data>
+  <data name="ThrowHelper_Requirement_Is_Missing" xml:space="preserve">
+    <value>The variable value `{0}` was not provided but is required.</value>
+  </data>
 </root>

src/HotChocolate/Fusion/src/Core/Metadata/FusionGraphConfiguration.cs

@@ -35,7 +35,7 @@ public FusionGraphConfiguration(
             {
                 if (!binding.Name.EqualsOrdinal(type.Name))
                 {
-                    _typeNameLookup.Add((binding.SchemaName, binding.Name), type.Name);
+                    _typeNameLookup.Add((binding.SubgraphName, binding.Name), type.Name);
                 }
             }
         }

src/HotChocolate/Fusion/src/Core/Metadata/FusionGraphConfigurationReader.cs

@@ -38,9 +38,10 @@ private FusionGraphConfiguration ReadServiceDefinition(DocumentNode document)
 
         var types = new List<IType>();
         var typeNames = FusionTypeNames.From(document);
+        var typeNameBindings = new Dictionary<string, MemberBinding>();
         var httpClientConfigs = ReadHttpClientConfigs(typeNames, schemaDef.Directives);
         var webSocketClientConfigs = ReadWebSocketClientConfigs(typeNames, schemaDef.Directives);
-        var typeNameField = CreateTypeNameField(_subgraphNames);
+        var typeNameField = CreateTypeNameField(typeNameBindings);
 
         foreach (var definition in document.Definitions)
         {
@@ -52,6 +53,11 @@ private FusionGraphConfiguration ReadServiceDefinition(DocumentNode document)
             }
         }
 
+        foreach (var subgraphName in _subgraphNames)
+        {
+            typeNameBindings.Add(subgraphName, new MemberBinding(subgraphName, typeNameField.Name));
+        }
+
         if (httpClientConfigs is not { Count: > 0 })
         {
             throw ServiceConfNoClientsSpecified();
@@ -102,13 +108,15 @@ private ObjectFieldCollection ReadObjectFields(
         return new ObjectFieldCollection(collection);
     }
 
-    private static ObjectField CreateTypeNameField(IEnumerable<string> subgraphNames)
-        => new ObjectField(
-            IntrospectionFields.TypeName,
-            new MemberBindingCollection(
-                subgraphNames.Select(t => new MemberBinding(t, IntrospectionFields.TypeName))),
-            FieldVariableDefinitionCollection.Empty,
-            ResolverDefinitionCollection.Empty);
+    private static ObjectField CreateTypeNameField(
+        Dictionary<string, MemberBinding> bindings)
+    {
+        return new ObjectField(
+                IntrospectionFields.TypeName,
+                new MemberBindingCollection(bindings),
+                FieldVariableDefinitionCollection.Empty,
+                ResolverDefinitionCollection.Empty);
+    }
 
     private IReadOnlyList<HttpClientConfiguration> ReadHttpClientConfigs(
         FusionTypeNames typeNames,
@@ -521,7 +529,7 @@ private MemberBindingCollection ReadMemberBindings(
 
             foreach (var binding in definitions)
             {
-                _assert.Add(binding.SchemaName);
+                _assert.Add(binding.SubgraphName);
             }
 
             foreach (var resolver in resolvers)

src/HotChocolate/Fusion/src/Core/Metadata/MemberBinding.cs

@@ -8,25 +8,40 @@ internal class MemberBinding
     /// <summary>
     /// Initializes a new instance of <see cref="MemberBinding"/>.
     /// </summary>
-    /// <param name="schemaName">
-    /// The schema to which the type system member is bound to.
+    /// <param name="subgraphName">
+    /// The name of the subgraph to which the type system member is bound to.
     /// </param>
     /// <param name="name">
-    /// The name which the type system member has in the <see cref="SchemaName"/>.
+    /// The name which the type system member has in the <see cref="SubgraphName"/>.
     /// </param>
-    public MemberBinding(string schemaName, string name)
+    public MemberBinding(string subgraphName, string name)
     {
-        SchemaName = schemaName;
+        if (string.IsNullOrWhiteSpace(subgraphName))
+        {
+            throw new ArgumentException(
+                $"'{nameof(subgraphName)}' cannot be null or whitespace.",
+                nameof(subgraphName));
+        }
+
+        if (string.IsNullOrWhiteSpace(name))
+        {
+            throw new ArgumentException(
+                $"'{nameof(name)}' cannot be null or whitespace.",
+                nameof(name));
+        }
+
+        SubgraphName = subgraphName;
         Name = name;
     }
 
     /// <summary>
-    /// Gets the schema to which the type system member is bound to.
+    /// Gets the name of the subgraph to which the type system member is bound to.
     /// </summary>
-    public string SchemaName { get; }
+    public string SubgraphName { get; }
 
     /// <summary>
-    /// Gets the name which the type system member has in the <see cref="SchemaName"/>.
+    /// Gets the name which the type system member has on a certain the subgraph
+    /// represented by the <see cref="SubgraphName" />.
     /// </summary>
     public string Name { get; }
 }

src/HotChocolate/Fusion/src/Core/Metadata/MemberBindingCollection.cs

@@ -9,7 +9,22 @@ internal sealed class MemberBindingCollection : IEnumerable<MemberBinding>
 
     public MemberBindingCollection(IEnumerable<MemberBinding> bindings)
     {
-        _bindings = bindings.ToDictionary(t => t.SchemaName, StringComparer.Ordinal);
+        if (bindings is null)
+        {
+            throw new ArgumentNullException(nameof(bindings));
+        }
+
+        _bindings = bindings.ToDictionary(t => t.SubgraphName, StringComparer.Ordinal);
+    }
+
+    public MemberBindingCollection(Dictionary<string, MemberBinding> bindings)
+    {
+        if (bindings is null)
+        {
+            throw new ArgumentNullException(nameof(bindings));
+        }
+
+        _bindings = bindings;
     }
 
     public int Count => _bindings.Count;

src/HotChocolate/Fusion/src/Core/Planning/ExecutionPlanBuilder.cs

@@ -1,9 +1,9 @@
 using System.Diagnostics;
-using System.Runtime.InteropServices.JavaScript;
 using HotChocolate.Execution.Processing;
 using HotChocolate.Fusion.Metadata;
 using HotChocolate.Language;
 using HotChocolate.Resolvers;
+using HotChocolate.Types.Introspection;
 using HotChocolate.Utilities;
 using static HotChocolate.Fusion.Metadata.ResolverKind;
 
@@ -97,7 +97,9 @@ private QueryPlanNode BuildQueryTree(QueryPlanContext context)
 
         while (current.Length > 0)
         {
-            if (current.Length is 1)
+            if (current.Length is 1 ||
+                (_schema.MutationType is not null &&
+                    _schema.MutationType.Name.EqualsOrdinal(current[0].Key.SelectionSetType.Name)))
             {
                 var node = current[0];
                 var selectionSet = ResolveSelectionSet(context, node.Key);
@@ -382,7 +384,8 @@ private SelectionSetNode CreateSelectionSetNode(
 
             foreach (var selection in selectionSet.Selections)
             {
-                if (executionStep.AllSelections.Contains(selection))
+                if (executionStep.AllSelections.Contains(selection) ||
+                    selection.Field.Name.EqualsOrdinal(IntrospectionFields.TypeName))
                 {
                     var field = typeContext.Fields[selection.Field.Name];
                     var selectionNode = CreateSelectionNode(
@@ -400,6 +403,12 @@ private SelectionSetNode CreateSelectionSetNode(
             {
                 selectionNodes.Add(selection);
             }
+
+            if(selectionNodes.Count == 0)
+            {
+                // TODO : ThrowHelper
+                throw new InvalidOperationException("A selection set must not be empty.");
+            }
         }
 
         return new SelectionSetNode(selectionNodes);