Fix stitching from and to interfaces (#1443)

* ExpandAbstractTypes to check transformed subschema

An abstract type may be present in the target schema, but renamed. ExpandAbstractTypes expands the abstract types not present in the target schema, but it should check the transformed target schema, to not be misled by renaming.

This may require manually passing the transformed schema in some cases. The default can stay to assume no renaming.

Within stitched schemas, the correct transformed schema can be saved to and then read from info.mergeInfo.transformedSchema.

* move ICreateRequest to delegate package with ICreateRequestFromInfo

* Add WrapConcreteTypes transform

= fixes #751

* allow redelegation of nested root query fields

in some circumstances

nested root fields may not always successfully stitch to subschemas, for example when the root field is a new  abstract field stitching to a concrete field or the reverse

* provide transformedSchema argument in more instances

= changes CreateResolverFn signature to take an options argument of type ICreateResolverOptions

packages/delegate/src/createRequest.ts

@@ -17,8 +17,8 @@ import {
   DocumentNode,
 } from 'graphql';
 
-import { Request, ICreateRequest, serializeInputValue, updateArgument } from '@graphql-tools/utils';
-import { ICreateRequestFromInfo } from './types';
+import { Request, serializeInputValue, updateArgument } from '@graphql-tools/utils';
+import { ICreateRequestFromInfo, ICreateRequest } from './types';
 
 export function getDelegatingOperation(parentType: GraphQLObjectType, schema: GraphQLSchema): OperationTypeNode {
   if (parentType === schema.getMutationType()) {

packages/delegate/src/delegateToSchema.ts

@@ -18,6 +18,7 @@ import {
 } from '@graphql-tools/utils';
 
 import ExpandAbstractTypes from './transforms/ExpandAbstractTypes';
+import WrapConcreteTypes from './transforms/WrapConcreteTypes';
 import FilterToSchema from './transforms/FilterToSchema';
 import AddReplacementSelectionSets from './transforms/AddReplacementSelectionSets';
 import AddReplacementFragments from './transforms/AddReplacementFragments';
@@ -76,6 +77,7 @@ function buildDelegationTransforms(
   args: Record<string, any>,
   returnType: GraphQLOutputType,
   transforms: Array<Transform>,
+  transformedSchema: GraphQLSchema,
   skipTypeMerging: boolean
 ): Array<Transform> {
   let delegationTransforms: Array<Transform> = [
@@ -89,9 +91,15 @@ function buildDelegationTransforms(
     );
   }
 
-  delegationTransforms = delegationTransforms.concat(transforms);
+  const transformedTargetSchema =
+    info.mergeInfo == null
+      ? transformedSchema ?? targetSchema
+      : transformedSchema ?? info.mergeInfo.transformedSchemas.get(subschemaOrSubschemaConfig) ?? targetSchema;
+
+  delegationTransforms.push(new WrapConcreteTypes(returnType, transformedTargetSchema));
+  delegationTransforms.push(new ExpandAbstractTypes(info.schema, transformedTargetSchema));
 
-  delegationTransforms.push(new ExpandAbstractTypes(info.schema, targetSchema));
+  delegationTransforms = delegationTransforms.concat(transforms);
 
   if (info.mergeInfo != null) {
     delegationTransforms.push(new AddReplacementFragments(targetSchema, info.mergeInfo.replacementFragments));
@@ -117,6 +125,7 @@ export function delegateRequest({
   returnType = info.returnType,
   context,
   transforms = [],
+  transformedSchema,
   skipValidation,
   skipTypeMerging,
 }: IDelegateRequestOptions) {
@@ -147,6 +156,7 @@ export function delegateRequest({
     args,
     returnType,
     requestTransforms.reverse(),
+    transformedSchema,
     skipTypeMerging
   );
 

packages/delegate/src/transforms/WrapConcreteTypes.ts

@@ -0,0 +1,95 @@
+import {
+  DocumentNode,
+  GraphQLSchema,
+  Kind,
+  getNamedType,
+  GraphQLOutputType,
+  isAbstractType,
+  TypeInfo,
+  visit,
+  visitWithTypeInfo,
+  isObjectType,
+  FieldNode,
+} from 'graphql';
+
+import { Transform, Request } from '@graphql-tools/utils';
+
+// For motivation, see https://github.com/ardatan/graphql-tools/issues/751
+
+export default class WrapConcreteTypes implements Transform {
+  private readonly returnType: GraphQLOutputType;
+  private readonly targetSchema: GraphQLSchema;
+
+  constructor(returnType: GraphQLOutputType, targetSchema: GraphQLSchema) {
+    this.returnType = returnType;
+    this.targetSchema = targetSchema;
+  }
+
+  public transformRequest(originalRequest: Request): Request {
+    const document = wrapConcreteTypes(this.returnType, this.targetSchema, originalRequest.document);
+    return {
+      ...originalRequest,
+      document,
+    };
+  }
+}
+
+function wrapConcreteTypes(
+  returnType: GraphQLOutputType,
+  targetSchema: GraphQLSchema,
+  document: DocumentNode
+): DocumentNode {
+  const namedType = getNamedType(returnType);
+
+  if (!isObjectType(namedType)) {
+    return document;
+  }
+
+  const queryRootType = targetSchema.getQueryType();
+  const mutationRootType = targetSchema.getMutationType();
+  const subscriptionRootType = targetSchema.getSubscriptionType();
+
+  const typeInfo = new TypeInfo(targetSchema);
+  const newDocument = visit(
+    document,
+    visitWithTypeInfo(typeInfo, {
+      [Kind.FIELD](node: FieldNode) {
+        const maybeType = typeInfo.getParentType();
+        if (maybeType == null) {
+          return false;
+        }
+
+        const parentType = getNamedType(maybeType);
+        if (parentType !== queryRootType && parentType !== mutationRootType && parentType !== subscriptionRootType) {
+          return false;
+        }
+
+        if (!isAbstractType(getNamedType(typeInfo.getType()))) {
+          return false;
+        }
+
+        return {
+          ...node,
+          selectionSet: {
+            kind: Kind.SELECTION_SET,
+            selections: [
+              {
+                kind: Kind.INLINE_FRAGMENT,
+                typeCondition: {
+                  kind: Kind.NAMED_TYPE,
+                  name: {
+                    kind: Kind.NAME,
+                    value: namedType.name,
+                  },
+                },
+                selectionSet: node.selectionSet,
+              },
+            ],
+          },
+        };
+      },
+    })
+  );
+
+  return newDocument;
+}

packages/delegate/src/types.ts

@@ -7,6 +7,9 @@ import {
   GraphQLResolveInfo,
   GraphQLFieldResolver,
   InlineFragmentNode,
+  FragmentDefinitionNode,
+  GraphQLObjectType,
+  VariableDefinitionNode,
 } from 'graphql';
 import { Operation, Transform, Request, TypeMap, ExecutionResult } from '@graphql-tools/utils';
 
@@ -22,6 +25,7 @@ export interface IDelegateToSchemaOptions<TContext = Record<string, any>, TArgs
   info: GraphQLResolveInfo;
   rootValue?: Record<string, any>;
   transforms?: Array<Transform>;
+  transformedSchema?: GraphQLSchema;
   skipValidation?: boolean;
   skipTypeMerging?: boolean;
 }
@@ -38,6 +42,19 @@ export interface ICreateRequestFromInfo {
   fieldNodes?: ReadonlyArray<FieldNode>;
 }
 
+export interface ICreateRequest {
+  sourceSchema?: GraphQLSchema;
+  sourceParentType?: GraphQLObjectType;
+  sourceFieldName?: string;
+  fragments?: Record<string, FragmentDefinitionNode>;
+  variableDefinitions?: ReadonlyArray<VariableDefinitionNode>;
+  variableValues?: Record<string, any>;
+  targetOperation: Operation;
+  targetFieldName: string;
+  selectionSet?: SelectionSetNode;
+  fieldNodes?: ReadonlyArray<FieldNode>;
+}
+
 export interface MergedTypeInfo {
   subschemas: Array<SubschemaConfig>;
   selectionSet?: SelectionSetNode;
@@ -70,12 +87,15 @@ export type Subscriber = <TReturn = Record<string, any>, TArgs = Record<string,
   params: ExecutionParams<TArgs, TContext>
 ) => Promise<AsyncIterator<ExecutionResult<TReturn>> | ExecutionResult<TReturn>>;
 
-export type CreateProxyingResolverFn = (
-  schema: GraphQLSchema | SubschemaConfig,
-  transforms: Array<Transform>,
-  operation: Operation,
-  fieldName: string
-) => GraphQLFieldResolver<any, any>;
+export interface ICreateProxyingResolverOptions {
+  schema: GraphQLSchema | SubschemaConfig;
+  transforms?: Array<Transform>;
+  transformedSchema?: GraphQLSchema;
+  operation?: Operation;
+  fieldName?: string;
+}
+
+export type CreateProxyingResolverFn = (options: ICreateProxyingResolverOptions) => GraphQLFieldResolver<any, any>;
 
 export interface SubschemaConfig {
   schema: GraphQLSchema;

packages/stitch/src/mergeInfo.ts

@@ -24,10 +24,12 @@ import { delegateToSchema, isSubschemaConfig, SubschemaConfig } from '@graphql-t
 import { MergeTypeCandidate, MergedTypeInfo, MergeInfo, MergeTypeFilter } from './types';
 
 export function createMergeInfo(
+  transformedSchemas: Map<GraphQLSchema | SubschemaConfig, GraphQLSchema>,
   typeCandidates: Record<string, Array<MergeTypeCandidate>>,
   mergeTypes?: boolean | Array<string> | MergeTypeFilter
 ): MergeInfo {
   return {
+    transformedSchemas,
     fragments: [],
     replacementSelectionSets: undefined,
     replacementFragments: undefined,

packages/stitch/src/stitchSchemas.ts

@@ -49,16 +49,6 @@ export function stitchSchemas({
     throw new Error('Expected `resolverValidationOptions` to be an object');
   }
 
-  const typeCandidates: Record<string, Array<MergeTypeCandidate>> = Object.create(null);
-  const extensions: Array<DocumentNode> = [];
-  const directives: Array<GraphQLDirective> = [];
-  const schemaDefs = Object.create(null);
-  const operationTypeNames = {
-    query: 'Query',
-    mutation: 'Mutation',
-    subscription: 'Subscription',
-  };
-
   let schemaLikeObjects: Array<GraphQLSchema | SubschemaConfig | DocumentNode | GraphQLNamedType> = [...subschemas];
   if (typeDefs) {
     schemaLikeObjects.push(buildDocumentFromTypeDefinitions(typeDefs, parseOptions));
@@ -78,8 +68,20 @@ export function stitchSchemas({
     }
   });
 
+  const transformedSchemas: Map<GraphQLSchema | SubschemaConfig, GraphQLSchema> = new Map();
+  const typeCandidates: Record<string, Array<MergeTypeCandidate>> = Object.create(null);
+  const extensions: Array<DocumentNode> = [];
+  const directives: Array<GraphQLDirective> = [];
+  const schemaDefs = Object.create(null);
+  const operationTypeNames = {
+    query: 'Query',
+    mutation: 'Mutation',
+    subscription: 'Subscription',
+  };
+
   buildTypeCandidates({
     schemaLikeObjects,
+    transformedSchemas,
     typeCandidates,
     extensions,
     directives,
@@ -90,7 +92,7 @@ export function stitchSchemas({
 
   let mergeInfo: MergeInfo;
 
-  mergeInfo = createMergeInfo(typeCandidates, mergeTypes);
+  mergeInfo = createMergeInfo(transformedSchemas, typeCandidates, mergeTypes);
 
   const typeMap = buildTypeMap({
     typeCandidates,

packages/stitch/src/typeCandidates.ts

@@ -43,6 +43,7 @@ function isDocumentNode(schemaLikeObject: any): schemaLikeObject is DocumentNode
 
 export function buildTypeCandidates({
   schemaLikeObjects,
+  transformedSchemas,
   typeCandidates,
   extensions,
   directives,
@@ -51,6 +52,7 @@ export function buildTypeCandidates({
   mergeDirectives,
 }: {
   schemaLikeObjects: Array<GraphQLSchema | SubschemaConfig | DocumentNode | GraphQLNamedType>;
+  transformedSchemas: Map<GraphQLSchema | SubschemaConfig, GraphQLSchema>;
   typeCandidates: Record<string, Array<MergeTypeCandidate>>;
   extensions: Array<DocumentNode>;
   directives: Array<GraphQLDirective>;
@@ -80,6 +82,8 @@ export function buildTypeCandidates({
     if (isSchema(schemaLikeObject) || isSubschemaConfig(schemaLikeObject)) {
       const schema = wrapSchema(schemaLikeObject);
 
+      transformedSchemas.set(schemaLikeObject, schema);
+
       const operationTypes = {
         query: schema.getQueryType(),
         mutation: schema.getMutationType(),

packages/stitch/src/types.ts

@@ -29,6 +29,7 @@ export interface MergedTypeInfo {
 }
 
 export interface MergeInfo {
+  transformedSchemas: Map<GraphQLSchema | SubschemaConfig, GraphQLSchema>;
   fragments: Array<{
     field: string;
     fragment: string;