Aligned Fusion more with the Fusion spec.

src/HotChocolate/Fusion/src/Abstractions/FusionEnumValueNames.cs

@@ -6,22 +6,17 @@ namespace HotChocolate.Fusion;
 internal static class FusionEnumValueNames
 {
     /// <summary>
-    /// Gets the name of the query resolver kind.
+    /// Gets the name of the fetch resolver kind.
     /// </summary>
-    public const string Query = "QUERY";
+    public const string Fetch = "FETCH";
 
     /// <summary>
     /// Gets the name of the batch resolver kind.
     /// </summary>
     public const string Batch = "BATCH";
 
     /// <summary>
-    /// Gets the name of the batch by key resolver kind.
+    /// Gets the name of the subscibe resolver kind.
     /// </summary>
-    public const string BatchByKey = "BATCH_BY_KEY";
-
-    /// <summary>
-    /// Gets the name of the subscription resolver kind.
-    /// </summary>
-    public const string Subscription = "SUBSCRIPTION";
+    public const string Subscribe = "SUBSCRIBE";
 }

src/HotChocolate/Fusion/src/Composition/Entities/EntityResolverKind.cs

@@ -4,6 +4,5 @@ public enum EntityResolverKind
 {
     Single = 0,
     Batch = 1,
-    BatchWithKey = 2,
-    Subscription = 3
+    Subscribe = 2
 }

src/HotChocolate/Fusion/src/Composition/FusionTypes.cs

@@ -144,10 +144,9 @@ private InputObjectType RegisterArgumentDefType(
     private EnumType RegisterResolverKindType(string name)
     {
         var resolverKind = new EnumType(name);
-        resolverKind.Values.Add(new EnumValue(FusionEnumValueNames.Query));
+        resolverKind.Values.Add(new EnumValue(FusionEnumValueNames.Fetch));
         resolverKind.Values.Add(new EnumValue(FusionEnumValueNames.Batch));
-        resolverKind.Values.Add(new EnumValue(FusionEnumValueNames.BatchByKey));
-        resolverKind.Values.Add(new EnumValue(FusionEnumValueNames.Subscription));
+        resolverKind.Values.Add(new EnumValue(FusionEnumValueNames.Subscribe));
         resolverKind.ContextData.Add(WellKnownContextData.IsFusionType, true);
         _fusionGraph.Types.Add(resolverKind);
         return resolverKind;
@@ -237,8 +236,7 @@ public Directive CreateResolverDirective(
             var kindValue = kind switch
             {
                 EntityResolverKind.Batch => FusionEnumValueNames.Batch,
-                EntityResolverKind.BatchWithKey => FusionEnumValueNames.BatchByKey,
-                EntityResolverKind.Subscription => FusionEnumValueNames.Subscription,
+                EntityResolverKind.Subscribe => FusionEnumValueNames.Subscribe,
                 _ => throw new NotSupportedException()
             };
 
@@ -256,12 +254,11 @@ private DirectiveType RegisterResolverDirectiveType(
         EnumType resolverKind)
     {
         var directiveType = new DirectiveType(name);
+        directiveType.Locations |= DirectiveLocation.Object;
         directiveType.Arguments.Add(new InputField(SelectArg, new NonNullType(selectionSet)));
         directiveType.Arguments.Add(new InputField(SubgraphArg, new NonNullType(typeName)));
-        directiveType.Arguments.Add(
-            new InputField(ArgumentsArg, new ListType(new NonNullType(argumentDef))));
+        directiveType.Arguments.Add(new InputField(ArgumentsArg, new ListType(new NonNullType(argumentDef))));
         directiveType.Arguments.Add(new InputField(KindArg, resolverKind));
-        directiveType.Locations |= DirectiveLocation.Object;
         directiveType.ContextData.Add(WellKnownContextData.IsFusionType, true);
         _fusionGraph.DirectiveTypes.Add(directiveType);
         return directiveType;
@@ -279,11 +276,25 @@ public Directive CreateSourceDirective(string subgraphName, string? originalName
 
     private DirectiveType RegisterSourceDirectiveType(string name, ScalarType typeName)
     {
-        var directiveType = new DirectiveType(name);
-        directiveType.Locations = DirectiveLocation.FieldDefinition;
-        directiveType.Arguments.Add(new InputField(SubgraphArg, new NonNullType(typeName)));
-        directiveType.Arguments.Add(new InputField(NameArg, typeName));
-        directiveType.ContextData.Add(WellKnownContextData.IsFusionType, true);
+        var directiveType = new DirectiveType(name)
+        {
+            Locations = DirectiveLocation.Object |
+                DirectiveLocation.FieldDefinition |
+                DirectiveLocation.Enum |
+                DirectiveLocation.EnumValue |
+                DirectiveLocation.InputObject |
+                DirectiveLocation.InputFieldDefinition |
+                DirectiveLocation.Scalar,
+            Arguments =
+            {
+                new InputField(SubgraphArg, new NonNullType(typeName)),
+                new InputField(NameArg, typeName)
+            },
+            ContextData =
+            {
+                [WellKnownContextData.IsFusionType] = true
+            }
+        };
         _fusionGraph.DirectiveTypes.Add(directiveType);
         return directiveType;
     }

src/HotChocolate/Fusion/src/Composition/Pipeline/Enrichers/NodeEntityEnricher.cs

@@ -142,7 +142,7 @@ private static void ResolveWithNodes(
 
         // Create a new EntityResolver for the entity
         var resolver = new EntityResolver(
-            EntityResolverKind.BatchWithKey,
+            EntityResolverKind.Batch,
             selectionSet,
             sourceType.Name,
             sourceSchema.Name);

src/HotChocolate/Fusion/src/Composition/Pipeline/Enrichers/PatternEntityEnricher.cs

@@ -213,7 +213,7 @@ private static void TryRegisterBatchEntityResolver(
 
             // Create a new EntityResolver for the entity
             var resolver = new EntityResolver(
-                EntityResolverKind.BatchWithKey,
+                EntityResolverKind.Batch,
                 selectionSet,
                 entityType.Name,
                 schema.Name);

src/HotChocolate/Fusion/src/Composition/Pipeline/Enrichers/RefResolverEntityEnricher.cs

@@ -54,7 +54,7 @@ public ValueTask EnrichAsync(
 
                         // Create a new EntityResolver for the entity
                         var resolver = new EntityResolver(
-                            EntityResolverKind.BatchWithKey,
+                            EntityResolverKind.Batch,
                             selectionSet,
                             type.Name,
                             schema.Name);
@@ -92,6 +92,7 @@ private static void TryRegisterEntityResolver(
         if ((entityResolverField.Type == entityType ||
                 (entityResolverField.Type.Kind is TypeKind.NonNull &&
                     entityResolverField.Type.InnerType() == entityType)) &&
+            entityResolverField.Arguments.Count > 0 &&
             entityResolverField.Arguments.All(t => t.ContainsIsDirective()))
         {
             var arguments = new List<ArgumentNode>();

src/HotChocolate/Fusion/src/Composition/Pipeline/MergeSubscriptionTypeMiddleware.cs

@@ -108,7 +108,7 @@ private static Directive CreateResolverDirective(
             subgraphName,
             selectionSet,
             arguments,
-            EntityResolverKind.Subscription);
+            EntityResolverKind.Subscribe);
 
     private static Directive CreateVariableDirective(
         CompositionContext context,

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

@@ -453,10 +453,9 @@ private ResolverDefinition ReadResolverDefinition(
                 case KindArg:
                     kind = Expect<StringValueNode>(argument.Value).Value switch
                     {
-                        FusionEnumValueNames.Query => ResolverKind.Query,
+                        FusionEnumValueNames.Fetch => ResolverKind.Query,
                         FusionEnumValueNames.Batch => ResolverKind.Batch,
-                        FusionEnumValueNames.BatchByKey => ResolverKind.BatchByKey,
-                        FusionEnumValueNames.Subscription => ResolverKind.Subscription,
+                        FusionEnumValueNames.Subscribe => ResolverKind.Subscribe,
                         _ => throw new InvalidOperationException(
                             FusionGraphConfigurationReader_ReadResolverDefinition_InvalidKindValue)
                     };

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

@@ -4,6 +4,5 @@ internal enum ResolverKind
 {
     Query,
     Batch,
-    BatchByKey,
-    Subscription,
+    Subscribe,
 }

src/HotChocolate/Fusion/src/Core/Planning/Pipeline/ExecutionNodeBuilderMiddleware.cs

@@ -7,7 +7,6 @@
 using HotChocolate.Types;
 using HotChocolate.Utilities;
 using static HotChocolate.Fusion.FusionResources;
-using static HotChocolate.Fusion.Metadata.ResolverKind;
 
 namespace HotChocolate.Fusion.Planning.Pipeline;
 
@@ -42,14 +41,14 @@ public void Invoke(QueryPlanContext context, QueryPlanDelegate next)
                 continue;
             }
 
-            if (selectionStep.Resolver?.Kind == BatchByKey)
+            if (selectionStep.Resolver?.Kind == ResolverKind.Batch)
             {
                 var resolve = CreateResolveByKeyBatchNode(context, selectionStep);
                 context.RegisterNode(resolve, selectionStep);
             }
             else if (selectionStep.Resolver is null &&
                 selectionStep.RootSelections.Count == 1 &&
-                selectionStep.RootSelections[0].Resolver?.Kind is Subscription)
+                selectionStep.RootSelections[0].Resolver?.Kind is ResolverKind.Subscribe)
             {
                 var resolve = CreateSubscribeNode(context, selectionStep);
                 context.RegisterNode(resolve, selectionStep);

src/HotChocolate/Fusion/src/Core/Planning/Pipeline/ExecutionStepDiscoveryMiddleware.cs

@@ -602,7 +602,7 @@ private static bool TryGetResolver(
                 {
                     if (preference is PreferredResolverKind.Subscription)
                     {
-                        if (current.Kind is ResolverKind.Subscription)
+                        if (current.Kind is ResolverKind.Subscribe)
                         {
                             resolver = current;
                             return true;
@@ -616,15 +616,6 @@ private static bool TryGetResolver(
                         {
                             case ResolverKind.Batch:
                                 resolver = current;
-
-                                if (preference is PreferredResolverKind.Batch)
-                                {
-                                    return true;
-                                }
-                                break;
-
-                            case ResolverKind.BatchByKey:
-                                resolver = current;
                                 break;
 
                             default:

src/HotChocolate/Fusion/src/Core/Planning/Pipeline/FieldRequirementsPlannerMiddleware.cs

@@ -250,8 +250,7 @@ private static ResolverDefinition SelectResolver(
             if (requirements > resolver.Requires.Count || selectedResolver is null ||
                 (selectedResolver.Requires.Count == resolver.Requires.Count &&
                     selectedResolver.Kind == ResolverKind.Query &&
-                    (resolver.Kind == ResolverKind.Batch ||
-                        resolver.Kind == ResolverKind.BatchByKey)))
+                    resolver.Kind == ResolverKind.Batch))
             {
                 requirements = resolver.Requires.Count;
                 selectedResolver = resolver;

src/HotChocolate/Fusion/src/Core/Planning/Pipeline/RequirementsPlannerMiddleware.cs

@@ -165,7 +165,7 @@ currentStep.ParentSelection is { } parent &&
 
                 // if we do by key batching the current execution step must
                 // re-export its requirements so we know where entities belong to.
-                if (currentStep.Resolver.Kind is ResolverKind.BatchByKey)
+                if (currentStep.Resolver.Kind is ResolverKind.Batch)
                 {
                     foreach (var variable in step.SelectionSetTypeMetadata.Variables)
                     {

src/HotChocolate/Fusion/test/CommandLine.Tests/__snapshots__/ComposeCommandTests.Compose_Fusion_Graph.snap

@@ -9,6 +9,7 @@ type Query {
   userById(id: ID!): User
   users: [User!]!
   usersById(ids: [ID!]!): [User!]!
+  viewer: Viewer!
 }
 
 type Mutation {
@@ -19,13 +20,22 @@ type AddUserPayload {
   user: User
 }
 
+type SomeData {
+  accountValue: String!
+}
+
 type User implements Node {
   birthdate: Date!
   id: ID!
   name: String!
   username: String!
 }
 
+type Viewer {
+  data: SomeData!
+  user: User
+}
+
 interface Node {
   id: ID!
 }
@@ -54,6 +64,7 @@ type Query {
   userById(id: ID!): User @variable(subgraph: "Accounts", name: "id", argument: "id") @resolver(subgraph: "Accounts", select: "{ userById(id: $id) }", arguments: [ { name: "id", type: "ID!" } ])
   users: [User!]! @resolver(subgraph: "Accounts", select: "{ users }")
   usersById(ids: [ID!]!): [User!]! @variable(subgraph: "Accounts", name: "ids", argument: "ids") @resolver(subgraph: "Accounts", select: "{ usersById(ids: $ids) }", arguments: [ { name: "ids", type: "[ID!]!" } ])
+  viewer: Viewer! @resolver(subgraph: "Accounts", select: "{ viewer }")
 }
 
 type Mutation {
@@ -64,13 +75,22 @@ type AddUserPayload {
   user: User @source(subgraph: "Accounts")
 }
 
-type User implements Node @variable(subgraph: "Accounts", name: "User_id", select: "id") @resolver(subgraph: "Accounts", select: "{ userById(id: $User_id) }", arguments: [ { name: "User_id", type: "ID!" } ]) @resolver(subgraph: "Accounts", select: "{ usersById(ids: $User_id) }", arguments: [ { name: "User_id", type: "[ID!]!" } ], kind: "BATCH_BY_KEY") @resolver(subgraph: "Accounts", select: "{ userById(id: $User_id) }", arguments: [ { name: "User_id", type: "ID!" } ]) @resolver(subgraph: "Accounts", select: "{ node(id: $User_id) { ... on User { ... User } } }", arguments: [ { name: "User_id", type: "ID!" } ]) @resolver(subgraph: "Accounts", select: "{ nodes(ids: $User_id) { ... on User { ... User } } }", arguments: [ { name: "User_id", type: "[ID!]!" } ], kind: "BATCH_BY_KEY") {
+type SomeData {
+  accountValue: String! @source(subgraph: "Accounts")
+}
+
+type User implements Node @variable(subgraph: "Accounts", name: "User_id", select: "id") @resolver(subgraph: "Accounts", select: "{ userById(id: $User_id) }", arguments: [ { name: "User_id", type: "ID!" } ]) @resolver(subgraph: "Accounts", select: "{ usersById(ids: $User_id) }", arguments: [ { name: "User_id", type: "[ID!]!" } ], kind: "BATCH") @resolver(subgraph: "Accounts", select: "{ userById(id: $User_id) }", arguments: [ { name: "User_id", type: "ID!" } ]) @resolver(subgraph: "Accounts", select: "{ node(id: $User_id) { ... on User { ... User } } }", arguments: [ { name: "User_id", type: "ID!" } ]) @resolver(subgraph: "Accounts", select: "{ nodes(ids: $User_id) { ... on User { ... User } } }", arguments: [ { name: "User_id", type: "[ID!]!" } ], kind: "BATCH") {
   birthdate: Date! @source(subgraph: "Accounts")
   id: ID! @source(subgraph: "Accounts")
   name: String! @source(subgraph: "Accounts")
   username: String! @source(subgraph: "Accounts")
 }
 
+type Viewer {
+  data: SomeData! @source(subgraph: "Accounts")
+  user: User @source(subgraph: "Accounts")
+}
+
 interface Node {
   id: ID!
 }
@@ -92,7 +112,7 @@ Accounts Subgraph Configuration
 ---------------
 {
   "Name": "Accounts",
-  "Schema": "schema {\n  query: Query\n  mutation: Mutation\n}\n\n\"The node interface is implemented by entities that have a global unique identifier.\"\ninterface Node {\n  id: ID!\n}\n\ntype Query {\n  \"Fetches an object given its ID.\"\n  node(\"ID of the object.\" id: ID!): Node\n  \"Lookup nodes by a list of IDs.\"\n  nodes(\"The list of node IDs.\" ids: [ID!]!): [Node]!\n  users: [User!]!\n  userById(id: ID!): User\n  usersById(ids: [ID!]!): [User!]!\n}\n\ntype Mutation {\n  addUser(input: AddUserInput!): AddUserPayload!\n}\n\ntype User implements Node {\n  id: ID!\n  name: String!\n  birthdate: Date!\n  username: String!\n}\n\n\"The `DateTime` scalar represents an ISO-8601 compliant date time type.\"\nscalar DateTime\n\n\"The `Date` scalar represents an ISO-8601 compliant date type.\"\nscalar Date\n\ninput AddUserInput {\n  name: String!\n  username: String!\n  birthdate: DateTime!\n}\n\ntype AddUserPayload {\n  user: User\n}",
+  "Schema": "schema {\n  query: Query\n  mutation: Mutation\n}\n\n\"The node interface is implemented by entities that have a global unique identifier.\"\ninterface Node {\n  id: ID!\n}\n\ntype Query {\n  \"Fetches an object given its ID.\"\n  node(\"ID of the object.\" id: ID!): Node\n  \"Lookup nodes by a list of IDs.\"\n  nodes(\"The list of node IDs.\" ids: [ID!]!): [Node]!\n  users: [User!]!\n  userById(id: ID!): User\n  usersById(ids: [ID!]!): [User!]!\n  viewer: Viewer!\n}\n\ntype Mutation {\n  addUser(input: AddUserInput!): AddUserPayload!\n}\n\ntype User implements Node {\n  id: ID!\n  name: String!\n  birthdate: Date!\n  username: String!\n}\n\ntype Viewer {\n  user: User\n  data: SomeData!\n}\n\n\"The `DateTime` scalar represents an ISO-8601 compliant date time type.\"\nscalar DateTime\n\n\"The `Date` scalar represents an ISO-8601 compliant date type.\"\nscalar Date\n\ntype SomeData {\n  accountValue: String!\n}\n\ninput AddUserInput {\n  name: String!\n  username: String!\n  birthdate: DateTime!\n}\n\ntype AddUserPayload {\n  user: User\n}",
   "Extensions": [
     "extend type Query {\n  userById(id: ID!\n    @is(field: \"id\")): User!\n  usersById(ids: [ID!]!\n    @is(field: \"id\")): [User!]!\n}"
   ],