[Fusion] Do not apply "InferKeysFromLookups" to invalid lookup fields

src/HotChocolate/Fusion/src/Fusion.Composition/SourceSchemaPreprocessor.cs

@@ -388,7 +388,15 @@ private void InferKeysFromLookups()
         var lookupFieldDefinitions =
             schema.Types
                 .OfType<MutableComplexTypeDefinition>()
-                .SelectMany(t => t.Fields.AsEnumerable().Where(f => f.Directives.ContainsName(Lookup)));
+                .SelectMany(t => t.Fields.AsEnumerable().Where(f =>
+                {
+                    if (f.Arguments.Count == 0 || f.Type.IsNonNullType() || f.Type.IsListType())
+                    {
+                        return false;
+                    }
+
+                    return f.Directives.ContainsName(Lookup);
+                }));
 
         foreach (var lookupFieldDefinition in lookupFieldDefinitions)
         {

src/HotChocolate/Fusion/test/Fusion.AspNetCore.Tests/AbstractTypeTests.cs

@@ -1272,7 +1272,7 @@ public IEnumerable<SharedType> InterfaceConnection()
                 => [new Discussion(1)];
 
             [Lookup]
-            public Author GetAuthorById(int id) => new Author(id);
+            public Author? GetAuthorById(int id) => new Author(id);
         }
 
         [InterfaceType]
@@ -1300,7 +1300,7 @@ public static class SourceSchema2
         public class Query
         {
             [Lookup]
-            public OtherInterface GetOtherInterface(int id)
+            public OtherInterface? GetOtherInterface(int id)
                 => new Author(id, id * 5);
 
             [Lookup]

src/HotChocolate/Fusion/test/Fusion.AspNetCore.Tests/BookStoreTests.cs

@@ -629,7 +629,7 @@ public class Query
                 };
 
             [Lookup]
-            public Book GetBookById(int id)
+            public Book? GetBookById(int id)
                 => _books[id];
 
             [UsePaging]
@@ -684,12 +684,12 @@ public Query()
 
             [Internal]
             [Lookup]
-            public Book GetBookById(int id)
+            public Book? GetBookById(int id)
                 => _books[id];
 
             [Internal]
             [Lookup]
-            public Author GetAuthorById(int id)
+            public Author? GetAuthorById(int id)
                 => _authors[id];
 
             [UsePaging]

src/HotChocolate/Fusion/test/Fusion.AspNetCore.Tests/DiagnisticListenerTests.cs

@@ -80,7 +80,7 @@ public class Query
                 };
 
             [Lookup]
-            public Book GetBookById(int id)
+            public Book? GetBookById(int id)
                 => _books[id];
 
             [UsePaging]
@@ -128,12 +128,12 @@ public Query()
 
             [Internal]
             [Lookup]
-            public Book GetBookById(int id)
+            public Book? GetBookById(int id)
                 => _books[id];
 
             [Internal]
             [Lookup]
-            public Author GetAuthorById(int id)
+            public Author? GetAuthorById(int id)
                 => _authors[id];
 
             [UsePaging]

src/HotChocolate/Fusion/test/Fusion.AspNetCore.Tests/InaccessibleTests.cs

@@ -916,7 +916,7 @@ public class Query
                     };
 
                 [Lookup]
-                public Book GetBookById(int id)
+                public Book? GetBookById(int id)
                     => _books[id];
 
                 public string GetInaccessibleText(
@@ -943,7 +943,7 @@ public class Query
 
                 [Internal]
                 [Lookup]
-                public Author GetAuthorById(int id)
+                public Author? GetAuthorById(int id)
                     => _authors[id];
 
                 public SomeEnum GetEnumField(SomeEnum value)

src/HotChocolate/Fusion/test/Fusion.AspNetCore.Tests/IntrospectionTests.cs

@@ -539,7 +539,7 @@ public class Query
                 };
 
             [Lookup]
-            public Book GetBookById(int id)
+            public Book? GetBookById(int id)
                 => _books[id];
 
             [UsePaging]
@@ -578,7 +578,7 @@ public class Query
 
             [Internal]
             [Lookup]
-            public Author GetAuthorById(int id)
+            public Author? GetAuthorById(int id)
                 => _authors[id];
 
             [UsePaging]

src/HotChocolate/Fusion/test/Fusion.AspNetCore.Tests/K6ExecutionTests.cs

@@ -178,11 +178,11 @@ public sealed class ReviewsQuery
             => ReviewRepository.GetById(id);
 
         [Lookup, Internal]
-        public ReviewProduct GetProduct([ID] string upc)
+        public ReviewProduct? GetProduct([ID] string upc)
             => new() { Upc = upc };
 
         [Lookup, Internal]
-        public ReviewUser GetUser([ID] string id)
+        public ReviewUser? GetUser([ID] string id)
             => new() { Id = id };
     }
 

src/HotChocolate/Fusion/test/Fusion.AspNetCore.Tests/LookupTests.cs

@@ -184,7 +184,7 @@ public class InternalLookups
                 };
 
                 [Lookup]
-                public Author GetAuthorById([ID] int id)
+                public Author? GetAuthorById([ID] int id)
                     => _authors[id];
             }
 
@@ -241,7 +241,7 @@ public class InternalLookups
                 };
 
                 [Lookup, Internal]
-                public Author GetAuthor([Is("{ id } | { name }")] AuthorByInput by)
+                public Author? GetAuthor([Is("{ id } | { name }")] AuthorByInput by)
                 {
                     if (by.Id is not null)
                     {

src/HotChocolate/Fusion/test/Fusion.AspNetCore.Tests/MutationTests.cs

@@ -126,7 +126,7 @@ public static class SourceSchema2
         public class Query
         {
             [Internal, Lookup]
-            public Book GetBookById(int id) => new(id, "Abc");
+            public Book? GetBookById(int id) => new(id, "Abc");
         }
 
         public record Book(int Id, string Author);

src/HotChocolate/Fusion/test/Fusion.AspNetCore.Tests/OperationPlannerInterceptorTests.cs

@@ -134,7 +134,7 @@ public class Query
                 };
 
             [Lookup]
-            public Book GetBookById(int id)
+            public Book? GetBookById(int id)
                 => _books[id];
 
             [UsePaging]
@@ -182,12 +182,12 @@ public Query()
 
             [Internal]
             [Lookup]
-            public Book GetBookById(int id)
+            public Book? GetBookById(int id)
                 => _books[id];
 
             [Internal]
             [Lookup]
-            public Author GetAuthorById(int id)
+            public Author? GetAuthorById(int id)
                 => _authors[id];
 
             [UsePaging]

src/HotChocolate/Fusion/test/Fusion.AspNetCore.Tests/SourceSchemaErrorTests.cs

@@ -587,48 +587,6 @@ public async Task Error_On_Lookup_Leaf_In_List_NonNull(ErrorHandlingMode onError
         await MatchSnapshotAsync(gateway, request, result, postFix: "OnError_" + onError);
     }
 
-    [Theory]
-    [InlineData(ErrorHandlingMode.Propagate)]
-    [InlineData(ErrorHandlingMode.Null)]
-    public async Task No_Data_And_Error_With_Path_For_Lookup_Field_NonNull(ErrorHandlingMode onError)
-    {
-        // arrange
-        using var server1 = CreateSourceSchema(
-            "A",
-            b => b.AddQueryType<SourceSchema1.Query>());
-
-        using var server2 = CreateSourceSchema(
-            "B",
-            b => b.AddQueryType<SourceSchema4.Query>());
-
-        using var gateway = await CreateCompositeSchemaAsync(
-        [
-            ("A", server1),
-            ("B", server2)
-        ]);
-
-        // act
-        using var client = GraphQLHttpClient.Create(gateway.CreateClient());
-
-        var request = new OperationRequest(
-            """
-            {
-              topProduct {
-                price
-                name
-              }
-            }
-            """,
-            onError: onError);
-
-        using var result = await client.PostAsync(
-            request,
-            new Uri("http://localhost:5000/graphql"));
-
-        // assert
-        await MatchSnapshotAsync(gateway, request, result, postFix: "OnError_" + onError);
-    }
-
     [Theory]
     [InlineData(ErrorHandlingMode.Propagate)]
     [InlineData(ErrorHandlingMode.Null)]
@@ -993,7 +951,7 @@ public static class SourceSchema4
         public class Query
         {
             [Lookup]
-            public Product GetProductById(int id, IResolverContext context)
+            public Product? GetProductById(int id, IResolverContext context)
                 => throw new GraphQLException(ErrorBuilder.New().SetMessage("Could not resolve Product")
                     .SetPath(context.Path).Build());
         }
@@ -1023,7 +981,7 @@ public static class SourceSchema6
         public class Query
         {
             [Lookup]
-            public Product GetProductById(int id) => new(id);
+            public Product? GetProductById(int id) => new(id);
         }
 
         public record Product(int Id)

src/HotChocolate/Fusion/test/Fusion.AspNetCore.Tests/SubscriptionsOverHttpStoreTests.cs

@@ -85,7 +85,7 @@ public record Book(int Id, string Title);
         public class Query
         {
             [Internal, Lookup]
-            public Book GetBookById(int id)
+            public Book? GetBookById(int id)
             {
                 switch (id)
                 {

src/HotChocolate/Fusion/test/Fusion.AspNetCore.Tests/__snapshots__/AbstractTypeTests.Abstract_Type.yaml

@@ -91,7 +91,7 @@ sourceSchemas:
           "Returns the elements in the list that come before the specified cursor."
           before: String
         ): InterfaceConnectionConnection
-        authorById(id: Int!): Author! @lookup
+        authorById(id: Int!): Author @lookup
       }
     interactions:
       - request:

src/HotChocolate/Fusion/test/Fusion.AspNetCore.Tests/__snapshots__/AbstractTypeTests.Abstract_Type_Direct_Source_Schema_Call.yaml

@@ -96,7 +96,7 @@ sourceSchemas:
           "Returns the elements in the list that come before the specified cursor."
           before: String
         ): InterfaceConnectionConnection
-        authorById(id: Int!): Author! @lookup
+        authorById(id: Int!): Author @lookup
       }
     interactions:
       - request:

src/HotChocolate/Fusion/test/Fusion.AspNetCore.Tests/__snapshots__/AbstractTypeTests.Abstract_Type_With_Abstract_Lookup.yaml

@@ -90,7 +90,7 @@ sourceSchemas:
           "Returns the elements in the list that come before the specified cursor."
           before: String
         ): InterfaceConnectionConnection
-        authorById(id: Int!): Author! @lookup
+        authorById(id: Int!): Author @lookup
       }
     interactions:
       - request:
@@ -139,7 +139,7 @@ sourceSchemas:
       }
 
       type Query {
-        otherInterface(id: Int!): OtherInterface! @lookup
+        otherInterface(id: Int!): OtherInterface @lookup
         discussionById(id: ID!): Discussion @lookup @internal
       }
     interactions:

src/HotChocolate/Fusion/test/Fusion.AspNetCore.Tests/__snapshots__/AbstractTypeTests.Abstract_Type_With_Concrete_Lookup.yaml

@@ -90,7 +90,7 @@ sourceSchemas:
           "Returns the elements in the list that come before the specified cursor."
           before: String
         ): InterfaceConnectionConnection
-        authorById(id: Int!): Author! @lookup
+        authorById(id: Int!): Author @lookup
       }
     interactions:
       - request:
@@ -139,7 +139,7 @@ sourceSchemas:
       }
 
       type Query {
-        otherInterface(id: Int!): OtherInterface! @lookup
+        otherInterface(id: Int!): OtherInterface @lookup
         discussionById(id: ID!): Discussion @lookup @internal
       }
     interactions:

src/HotChocolate/Fusion/test/Fusion.AspNetCore.Tests/__snapshots__/AbstractTypeTests.Concrete_Type_With_Abstract_Lookup.yaml

@@ -86,7 +86,7 @@ sourceSchemas:
           "Returns the elements in the list that come before the specified cursor."
           before: String
         ): InterfaceConnectionConnection
-        authorById(id: Int!): Author! @lookup
+        authorById(id: Int!): Author @lookup
       }
     interactions:
       - request:
@@ -130,7 +130,7 @@ sourceSchemas:
       }
 
       type Query {
-        otherInterface(id: Int!): OtherInterface! @lookup
+        otherInterface(id: Int!): OtherInterface @lookup
         discussionById(id: ID!): Discussion @lookup @internal
       }
     interactions:

src/HotChocolate/Fusion/test/Fusion.AspNetCore.Tests/__snapshots__/AbstractTypeTests.List_Of_Abstract_Types.yaml

@@ -100,7 +100,7 @@ sourceSchemas:
           "Returns the elements in the list that come before the specified cursor."
           before: String
         ): InterfaceConnectionConnection
-        authorById(id: Int!): Author! @lookup
+        authorById(id: Int!): Author @lookup
       }
     interactions:
       - request:

src/HotChocolate/Fusion/test/Fusion.AspNetCore.Tests/__snapshots__/BookStoreTests.Ensure_String_Literals_Can_Be_Empty.yaml

@@ -59,7 +59,7 @@ sourceSchemas:
       }
 
       type Query {
-        bookById(id: Int!): Book! @lookup
+        bookById(id: Int!): Book @lookup
         books(
           "Returns the first _n_ elements from the list."
           first: Int
@@ -136,8 +136,8 @@ sourceSchemas:
       }
 
       type Query {
-        bookById(id: Int!): Book! @internal @lookup
-        authorById(id: Int!): Author! @internal @lookup
+        bookById(id: Int!): Book @internal @lookup
+        authorById(id: Int!): Author @internal @lookup
         authors(
           "Returns the first _n_ elements from the list."
           first: Int

src/HotChocolate/Fusion/test/Fusion.AspNetCore.Tests/__snapshots__/BookStoreTests.Ensure_String_Variables_Can_Be_Empty.yaml

@@ -63,7 +63,7 @@ sourceSchemas:
       }
 
       type Query {
-        bookById(id: Int!): Book! @lookup
+        bookById(id: Int!): Book @lookup
         books(
           "Returns the first _n_ elements from the list."
           first: Int
@@ -144,8 +144,8 @@ sourceSchemas:
       }
 
       type Query {
-        bookById(id: Int!): Book! @internal @lookup
-        authorById(id: Int!): Author! @internal @lookup
+        bookById(id: Int!): Book @internal @lookup
+        authorById(id: Int!): Author @internal @lookup
         authors(
           "Returns the first _n_ elements from the list."
           first: Int