[federation] rename _FieldSet to FieldSet in Federation v2 (#1547) (#1618)

* [federation] rename _FieldSet to FieldSet in Federation v2

Per [Apollo Specification](https://www.apollographql.com/docs/federation/federation-spec), `_FieldSet` was renamed to `FieldSet` in Federation v2.

Resolves: #1512

* ktlint - unused imports

Co-authored-by: Dariusz Kuc <[email protected]>

Author: hrkfdn

generator/graphql-kotlin-federation/src/main/kotlin/com/expediagroup/graphql/generator/federation/FederatedSchemaGeneratorHooks.kt

@@ -42,11 +42,11 @@ import com.expediagroup.graphql.generator.federation.directives.appliedLinkDirec
 import com.expediagroup.graphql.generator.federation.exception.IncorrectFederatedDirectiveUsage
 import com.expediagroup.graphql.generator.federation.execution.EntityResolver
 import com.expediagroup.graphql.generator.federation.execution.FederatedTypeResolver
-import com.expediagroup.graphql.generator.federation.extensions.addDirectivesIfNotPresent
 import com.expediagroup.graphql.generator.federation.types.ANY_SCALAR_TYPE
 import com.expediagroup.graphql.generator.federation.types.ENTITY_UNION_NAME
 import com.expediagroup.graphql.generator.federation.types.FIELD_SET_SCALAR_NAME
 import com.expediagroup.graphql.generator.federation.types.FIELD_SET_SCALAR_TYPE
+import com.expediagroup.graphql.generator.federation.types.FieldSetTransformer
 import com.expediagroup.graphql.generator.federation.types.SERVICE_FIELD_DEFINITION
 import com.expediagroup.graphql.generator.federation.types._Service
 import com.expediagroup.graphql.generator.federation.types.generateEntityFieldDefinition
@@ -60,6 +60,7 @@ import graphql.schema.GraphQLDirective
 import graphql.schema.GraphQLObjectType
 import graphql.schema.GraphQLSchema
 import graphql.schema.GraphQLType
+import graphql.schema.SchemaTransformer
 import kotlin.reflect.KType
 import kotlin.reflect.full.findAnnotation
 
@@ -133,40 +134,57 @@ open class FederatedSchemaGeneratorHooks(private val resolvers: List<FederatedTy
     }
 
     override fun willBuildSchema(builder: GraphQLSchema.Builder): GraphQLSchema.Builder {
+        val originalSchema = builder.build()
+        val originalQuery = originalSchema.queryType
+
+        findMissingFederationDirectives(originalSchema.directives).forEach {
+            builder.additionalDirective(it)
+        }
         if (optInFederationV2) {
-            val fed2Imports = federatedDirectiveV2List.map { "@${it.name}" }
-                .minus("@$LINK_DIRECTIVE_NAME")
+            val fed2Imports = federatedDirectiveV2List.map { it.name }
+                .minus(LINK_DIRECTIVE_NAME)
                 .plus(FIELD_SET_SCALAR_NAME)
 
             builder.withSchemaDirective(LINK_DIRECTIVE_TYPE)
                 .withSchemaAppliedDirective(appliedLinkDirective(FEDERATION_SPEC_URL, fed2Imports))
         }
 
-        val originalSchema = builder.build()
-        val originalQuery = originalSchema.queryType
         val federatedCodeRegistry = GraphQLCodeRegistry.newCodeRegistry(originalSchema.codeRegistry)
-
-        // Add all the federation directives if they are not present
-        val federatedSchemaBuilder = originalSchema.addDirectivesIfNotPresent(federatedDirectiveList())
-
-        // Register the data fetcher for the _service query
-        val sdl = getFederatedServiceSdl(originalSchema)
-        federatedCodeRegistry.dataFetcher(FieldCoordinates.coordinates(originalQuery.name, SERVICE_FIELD_DEFINITION.name), DataFetcher { _Service(sdl) })
-
-        // Add the _entities field to the query and register all the _Entity union types
-        val federatedQuery = GraphQLObjectType.newObject(originalQuery)
         val entityTypeNames = getFederatedEntities(originalSchema)
+        // Add the _entities field to the query and register all the _Entity union types
         if (entityTypeNames.isNotEmpty()) {
+            val federatedQuery = GraphQLObjectType.newObject(originalQuery)
+
             val entityField = generateEntityFieldDefinition(entityTypeNames)
             federatedQuery.field(entityField)
 
             federatedCodeRegistry.dataFetcher(FieldCoordinates.coordinates(originalQuery.name, entityField.name), EntityResolver(resolvers))
             federatedCodeRegistry.typeResolver(ENTITY_UNION_NAME) { env: TypeResolutionEnvironment -> env.schema.getObjectType(env.getObjectName()) }
-            federatedSchemaBuilder.additionalType(ANY_SCALAR_TYPE)
+
+            builder.query(federatedQuery)
+                .codeRegistry(federatedCodeRegistry.build())
+                .additionalType(ANY_SCALAR_TYPE)
+        }
+
+        val federatedBuilder = if (optInFederationV2) {
+            builder
+        } else {
+            // transform schema to rename FieldSet to _FieldSet
+            GraphQLSchema.newSchema(SchemaTransformer.transformSchema(builder.build(), FieldSetTransformer()))
         }
 
-        return federatedSchemaBuilder.query(federatedQuery.build())
-            .codeRegistry(federatedCodeRegistry.build())
+        // Register the data fetcher for the _service query
+        val sdl = getFederatedServiceSdl(federatedBuilder.build())
+        federatedCodeRegistry.dataFetcher(FieldCoordinates.coordinates(originalQuery.name, SERVICE_FIELD_DEFINITION.name), DataFetcher { _Service(sdl) })
+
+        return federatedBuilder.codeRegistry(federatedCodeRegistry.build())
+    }
+
+    private fun findMissingFederationDirectives(existingDirectives: List<GraphQLDirective>): List<GraphQLDirective> {
+        val existingDirectiveNames = existingDirectives.map { it.name }
+        return federatedDirectiveList().filter {
+            !existingDirectiveNames.contains(it.name)
+        }
     }
 
     private fun federatedDirectiveList(): List<GraphQLDirective> = if (optInFederationV2) {

generator/graphql-kotlin-federation/src/main/kotlin/com/expediagroup/graphql/generator/federation/extensions/graphQLSchemaExtensions.kt

@@ -28,8 +28,12 @@ import graphql.schema.CoercingSerializeException
 import graphql.schema.GraphQLArgument
 import graphql.schema.GraphQLNonNull
 import graphql.schema.GraphQLScalarType
+import graphql.schema.GraphQLSchemaElement
+import graphql.schema.GraphQLTypeVisitorStub
+import graphql.util.TraversalControl
+import graphql.util.TraverserContext
 
-internal const val FIELD_SET_SCALAR_NAME = "_FieldSet"
+internal const val FIELD_SET_SCALAR_NAME = "FieldSet"
 internal const val FIELD_SET_ARGUMENT_NAME = "fields"
 
 /**
@@ -72,3 +76,18 @@ private object FieldSetCoercing : Coercing<FieldSet, String> {
         throw CoercingValueToLiteralException(_FieldSet::class, input)
     }
 }
+
+/**
+ * Renames FieldSet scalar (used in Federation V2) to _FieldSet (used in Federation V1).
+ */
+class FieldSetTransformer : GraphQLTypeVisitorStub() {
+    override fun visitGraphQLScalarType(node: GraphQLScalarType, context: TraverserContext<GraphQLSchemaElement>): TraversalControl {
+        if (node.name == "FieldSet") {
+            val legacyFieldSetScalar = node.transform {
+                it.name("_FieldSet")
+            }
+            return changeNode(context, legacyFieldSetScalar)
+        }
+        return super.visitGraphQLScalarType(node, context)
+    }
+}

generator/graphql-kotlin-federation/src/main/kotlin/com/expediagroup/graphql/generator/federation/types/_FieldSet.kt renamed to generator/graphql-kotlin-federation/src/main/kotlin/com/expediagroup/graphql/generator/federation/types/FieldSet.kt

@@ -30,7 +30,7 @@ class FederatedSchemaV2GeneratorTest {
     fun `verify can generate federated schema`() {
         val expectedSchema =
             """
-            schema @link(import : ["@extends", "@external", "@inaccessible", "@key", "@override", "@provides", "@requires", "@shareable", "@tag", "_FieldSet"], url : "https://specs.apollo.dev/federation/v2.0"){
+            schema @link(import : ["extends", "external", "inaccessible", "key", "override", "provides", "requires", "shareable", "tag", "FieldSet"], url : "https://specs.apollo.dev/federation/v2.0"){
               query: Query
             }
 
@@ -58,7 +58,7 @@ class FederatedSchemaV2GeneratorTest {
               ) on FIELD | FRAGMENT_SPREAD | INLINE_FRAGMENT
 
             "Space separated list of primary keys needed to access federated object"
-            directive @key(fields: _FieldSet!, resolvable: Boolean = true) repeatable on OBJECT | INTERFACE
+            directive @key(fields: FieldSet!, resolvable: Boolean = true) repeatable on OBJECT | INTERFACE
 
             "Links definitions within the document to external schemas."
             directive @link(import: [String], url: String) repeatable on SCHEMA
@@ -67,10 +67,10 @@ class FederatedSchemaV2GeneratorTest {
             directive @override(from: String!) on FIELD_DEFINITION
 
             "Specifies the base type field set that will be selectable by the gateway"
-            directive @provides(fields: _FieldSet!) on FIELD_DEFINITION
+            directive @provides(fields: FieldSet!) on FIELD_DEFINITION
 
             "Specifies required input field set from the base type for a resolver"
-            directive @requires(fields: _FieldSet!) on FIELD_DEFINITION
+            directive @requires(fields: FieldSet!) on FIELD_DEFINITION
 
             "Indicates that given object and/or field can be resolved by multiple subgraphs"
             directive @shareable on OBJECT | FIELD_DEFINITION
@@ -133,11 +133,11 @@ class FederatedSchemaV2GeneratorTest {
               sdl: String!
             }
 
+            "Federation type representing set of fields"
+            scalar FieldSet
+
             "Federation scalar type used to represent any external entities passed to _entities query."
             scalar _Any
-
-            "Federation type representing set of fields"
-            scalar _FieldSet
             """.trimIndent()
 
         val config = FederatedSchemaGeneratorConfig(

generator/graphql-kotlin-federation/src/test/kotlin/com/expediagroup/graphql/generator/federation/FederatedSchemaV2GeneratorTest.kt

@@ -99,7 +99,7 @@ type SelfReferenceObject {
 
 const val FEDERATED_SERVICE_SDL_V2 =
 """
-schema @link(import : ["@extends", "@external", "@inaccessible", "@key", "@override", "@provides", "@requires", "@shareable", "@tag", "_FieldSet"], url : "https://specs.apollo.dev/federation/v2.0"){
+schema @link(import : ["extends", "external", "inaccessible", "key", "override", "provides", "requires", "shareable", "tag", "FieldSet"], url : "https://specs.apollo.dev/federation/v2.0"){
   query: Query
 }
 
@@ -111,21 +111,38 @@ directive @extends on OBJECT | INTERFACE
 "Marks target field as external meaning it will be resolved by federated schema"
 directive @external on FIELD_DEFINITION
 
+"Marks location within schema as inaccessible from the GraphQL Gateway"
+directive @inaccessible on SCALAR | OBJECT | FIELD_DEFINITION | ARGUMENT_DEFINITION | INTERFACE | UNION | ENUM | ENUM_VALUE | INPUT_OBJECT | INPUT_FIELD_DEFINITION
+
 "Space separated list of primary keys needed to access federated object"
-directive @key(fields: _FieldSet!, resolvable: Boolean = true) repeatable on OBJECT | INTERFACE
+directive @key(fields: FieldSet!, resolvable: Boolean = true) repeatable on OBJECT | INTERFACE
+
+"Links definitions within the document to external schemas."
+directive @link(import: [String], url: String) repeatable on SCHEMA
+
+"Overrides fields resolution logic from other subgraph. Used for migrating fields from one subgraph to another."
+directive @override(from: String!) on FIELD_DEFINITION
 
 "Specifies the base type field set that will be selectable by the gateway"
-directive @provides(fields: _FieldSet!) on FIELD_DEFINITION
+directive @provides(fields: FieldSet!) on FIELD_DEFINITION
 
 "Specifies required input field set from the base type for a resolver"
-directive @requires(fields: _FieldSet!) on FIELD_DEFINITION
+directive @requires(fields: FieldSet!) on FIELD_DEFINITION
+
+"Indicates that given object and/or field can be resolved by multiple subgraphs"
+directive @shareable on OBJECT | FIELD_DEFINITION
+
+"Allows users to annotate fields and types with additional metadata information"
+directive @tag(name: String!) repeatable on SCALAR | OBJECT | FIELD_DEFINITION | ARGUMENT_DEFINITION | INTERFACE | UNION | ENUM | ENUM_VALUE | INPUT_OBJECT | INPUT_FIELD_DEFINITION
 
 interface Product @extends @key(fields : "id", resolvable : true) @key(fields : "upc", resolvable : true) {
   id: String! @external
   reviews: [Review!]!
   upc: String! @external
 }
 
+union _Entity = Book | User
+
 type Book implements Product @extends @key(fields : "id", resolvable : true) @key(fields : "upc", resolvable : true) {
   author: User! @provides(fields : "name")
   id: String! @external
@@ -140,6 +157,8 @@ type CustomScalar {
 }
 
 type Query @extends {
+  "Union of all types that use the @key directive, including both types native to the schema and extended types"
+  _entities(representations: [_Any!]!): [_Entity]!
   _service: _Service!
 }
 
@@ -160,7 +179,10 @@ type _Service {
 }
 
 "Federation type representing set of fields"
-scalar _FieldSet
+scalar FieldSet
+
+"Federation scalar type used to represent any external entities passed to _entities query."
+scalar _Any
 """
 
 class ServiceQueryResolverTest {

generator/graphql-kotlin-federation/src/test/kotlin/com/expediagroup/graphql/generator/federation/execution/ServiceQueryResolverTest.kt

@@ -105,7 +105,7 @@ class Query {
 
 val config = FederatedSchemaGeneratorConfig(
   supportedPackages = "com.example",
-  hooks = FederatedSchemaGeneratorHooks(emptyList())
+  hooks = FederatedSchemaGeneratorHooks(emptyList(), optInFederationV2 = true)
 )
 
 toFederatedSchema(
@@ -119,7 +119,7 @@ will generate
 ```graphql
 # Federation spec types
 scalar _Any
-scalar _FieldSet
+scalar FieldSet
 
 union _Entity
 
@@ -128,9 +128,9 @@ type _Service {
 }
 
 directive @external on FIELD_DEFINITION
-directive @requires(fields: _FieldSet) on FIELD_DEFINITION
-directive @provides(fields: _FieldSet) on FIELD_DEFINITION
-directive @key(fields: _FieldSet) on OBJECT | INTERFACE
+directive @requires(fields: FieldSet) on FIELD_DEFINITION
+directive @provides(fields: FieldSet) on FIELD_DEFINITION
+directive @key(fields: FieldSet!, resolvable: Boolean = true) repeatable on OBJECT | INTERFACE
 directive @extends on OBJECT | INTERFACE
 
 # Schema types