Fixed mutation convention for ListType payload

src/HotChocolate/Core/src/Types.Mutations/MutationConventionTypeInterceptor.cs

@@ -430,7 +430,7 @@ private ITypeNode CreateTypeNode(IType type)
         => type switch
         {
             NonNullType nnt => new NonNullTypeNode((INullableTypeNode)CreateTypeNode(nnt.Type)),
-            ListType lt => new ListTypeNode((INullableTypeNode)CreateTypeNode(lt.ElementType)),
+            ListType lt => new ListTypeNode(CreateTypeNode(lt.ElementType)),
             INamedType nt => new NamedTypeNode(nt.Name),
             _ => throw new NotSupportedException("Type is not supported.")
         };

src/HotChocolate/Core/test/Types.Mutations.Tests/AnnotationBasedMutations.cs

@@ -29,6 +29,47 @@ public async Task SimpleMutation_Inferred()
             .MatchSnapshotAsync();
     }
 
+    [Fact]
+    public async Task SimpleMutationReturnList_Inferred()
+    {
+        Snapshot.FullName();
+
+        await new ServiceCollection()
+            .AddGraphQL()
+            .AddMutationType<SimpleMutationReturnList>()
+            .AddMutationConventions(
+                new MutationConventionOptions
+                {
+                    ApplyToAllMutations = true
+                })
+            .ModifyOptions(o => o.StrictValidation = false)
+            .BuildSchemaAsync()
+            .MatchSnapshotAsync();
+    }
+
+    [Fact]
+    public async Task SimpleMutationReturnList_Inferred_Execute()
+    {
+        Snapshot.FullName();
+
+        await new ServiceCollection()
+            .AddGraphQL()
+            .AddMutationType<SimpleMutationReturnList>()
+            .AddMutationConventions(
+                new MutationConventionOptions
+                {
+                    ApplyToAllMutations = true
+                })
+            .ModifyOptions(o => o.StrictValidation = false)
+            .ExecuteRequestAsync(
+                @"mutation {
+                    doSomething(input: { something: ""abc"" }) {
+                        string
+                    }
+                }")
+            .MatchSnapshotAsync();
+    }
+
     [Fact]
     public async Task SimpleMutation_Inferred_With_QueryField()
     {
@@ -397,6 +438,11 @@ public string DoSomething(string something)
             => something;
     }
 
+    public class SimpleMutationReturnList
+    {
+        public System.Collections.Generic.List<string> DoSomething(string something) => new() { something };
+    }
+
     [ExtendObjectType("Mutation")]
     public class SimpleMutationExtension
     {

src/HotChocolate/Core/test/Types.Mutations.Tests/__snapshots__/AnnotationBasedMutations.SimpleMutationReturnList_Inferred.snap

@@ -0,0 +1,21 @@
+schema {
+  mutation: SimpleMutationReturnList
+}
+
+type DoSomethingPayload {
+  string: [String!]
+}
+
+type SimpleMutationReturnList {
+  doSomething(input: DoSomethingInput!): DoSomethingPayload!
+}
+
+input DoSomethingInput {
+  something: String!
+}
+
+"The `@defer` directive may be provided for fragment spreads and inline fragments to inform the executor to delay the execution of the current fragment to indicate deprioritization of the current fragment. A query with `@defer` directive will cause the request to potentially return multiple responses, where non-deferred data is delivered in the initial response and data deferred is delivered in a subsequent response. `@include` and `@skip` take precedence over `@defer`."
+directive @defer("If this argument label has a value other than null, it will be passed on to the result of this defer directive. This label is intended to give client applications a way to identify to which fragment a deferred result belongs to." label: String "Deferred when true." if: Boolean) on FRAGMENT_SPREAD | INLINE_FRAGMENT
+
+"The `@stream` directive may be provided for a field of `List` type so that the backend can leverage technology such as asynchronous iterators to provide a partial list in the initial response, and additional list items in subsequent responses. `@include` and `@skip` take precedence over `@stream`."
+directive @stream("If this argument label has a value other than null, it will be passed on to the result of this stream directive. This label is intended to give client applications a way to identify to which fragment a streamed result belongs to." label: String "The initial elements that shall be send down to the consumer." initialCount: Int! = 0 "Streamed when true." if: Boolean) on FIELD

src/HotChocolate/Core/test/Types.Mutations.Tests/__snapshots__/AnnotationBasedMutations.SimpleMutationReturnList_Inferred_Execute.snap

@@ -0,0 +1,9 @@
+{
+  "data": {
+    "doSomething": {
+      "string": [
+        "abc"
+      ]
+    }
+  }
+}