From abe0ee84ebe23daefed2344f7c16c46b60d9b0b1 Mon Sep 17 00:00:00 2001
From: yaacovCR <yaacovCR@gmail.com>
Date: Wed, 15 Jan 2020 20:02:25 -0500
Subject: [PATCH] feat(stitching): add returnType option to delegateToSchema

facilitates proxying from objects to lists or possibly otherwise incompatible schemas, see #33.
---
 src/Interfaces.ts                            | 2 ++
 src/stitching/checkResultAndHandleErrors.ts  | 7 +++++--
 src/stitching/delegateToSchema.ts            | 3 ++-
 src/test/testDataloader.ts                   | 6 ++----
 src/transforms/CheckResultAndHandleErrors.ts | 8 ++++++--
 5 files changed, 17 insertions(+), 9 deletions(-)

diff --git a/src/Interfaces.ts b/src/Interfaces.ts
index 18240280c21..73446f5d737 100644
--- a/src/Interfaces.ts
+++ b/src/Interfaces.ts
@@ -20,6 +20,7 @@ import {
   GraphQLInterfaceType,
   GraphQLObjectType,
   InlineFragmentNode,
+  GraphQLOutputType,
 } from 'graphql';
 
 import { SchemaDirectiveVisitor } from './utils/SchemaDirectiveVisitor';
@@ -115,6 +116,7 @@ export interface IDelegateToSchemaOptions<TContext = { [key: string]: any }> {
   schema: GraphQLSchema | SubschemaConfig;
   operation: Operation;
   fieldName: string;
+  returnType?: GraphQLOutputType;
   args?: { [key: string]: any };
   context: TContext;
   info: IGraphQLToolsResolveInfo;
diff --git a/src/stitching/checkResultAndHandleErrors.ts b/src/stitching/checkResultAndHandleErrors.ts
index e13096248c5..d956ae255d5 100644
--- a/src/stitching/checkResultAndHandleErrors.ts
+++ b/src/stitching/checkResultAndHandleErrors.ts
@@ -9,6 +9,7 @@ import {
   GraphQLCompositeType,
   GraphQLError,
   GraphQLList,
+  GraphQLOutputType,
   GraphQLType,
   GraphQLSchema,
   FieldNode,
@@ -34,6 +35,7 @@ export function checkResultAndHandleErrors(
   info: GraphQLResolveInfo,
   responseKey?: string,
   subschema?: GraphQLSchema | SubschemaConfig,
+  returnType: GraphQLOutputType = info.returnType,
 ): any {
   if (!responseKey) {
     responseKey = getResponseKeyFromInfo(info);
@@ -43,7 +45,7 @@ export function checkResultAndHandleErrors(
   const data = result.data && result.data[responseKey];
   const subschemas = [subschema];
 
-  return handleResult(data, errors, subschemas, context, info);
+  return handleResult(data, errors, subschemas, context, info, returnType);
 }
 
 export function handleResult(
@@ -52,8 +54,9 @@ export function handleResult(
   subschemas: Array<GraphQLSchema | SubschemaConfig>,
   context: Record<string, any>,
   info: IGraphQLToolsResolveInfo,
+  returnType = info.returnType,
 ): any {
-  const type = getNullableType(info.returnType);
+  const type = getNullableType(returnType);
 
   if (result == null) {
     return handleNull(info.fieldNodes, responsePathAsArray(info.path), errors);
diff --git a/src/stitching/delegateToSchema.ts b/src/stitching/delegateToSchema.ts
index 78dd203ce99..44c83eb6b1e 100644
--- a/src/stitching/delegateToSchema.ts
+++ b/src/stitching/delegateToSchema.ts
@@ -65,6 +65,7 @@ function delegateToSchemaImplementation({
   info,
   operation = info.operation.operation,
   fieldName,
+  returnType = info.returnType,
   args,
   context,
   transforms = [],
@@ -101,7 +102,7 @@ function delegateToSchemaImplementation({
   };
 
   transforms = [
-    new CheckResultAndHandleErrors(info, fieldName, subschema, context),
+    new CheckResultAndHandleErrors(info, fieldName, subschema, context, returnType),
     ...transforms,
     new ExpandAbstractTypes(info.schema, targetSchema),
   ];
diff --git a/src/test/testDataloader.ts b/src/test/testDataloader.ts
index 173b927de14..7b2e90e38dc 100644
--- a/src/test/testDataloader.ts
+++ b/src/test/testDataloader.ts
@@ -81,10 +81,8 @@ describe('dataloader', () => {
           ids: keys.map((k: { id: any }) => k.id)
         },
         context: null,
-        info: {
-          ...keys[0].info,
-          returnType: new GraphQLList(keys[0].info.returnType),
-        }
+        info: keys[0].info,
+        returnType: new GraphQLList(keys[0].info.returnType),
       });
 
       expect(users).to.deep.equal([{
diff --git a/src/transforms/CheckResultAndHandleErrors.ts b/src/transforms/CheckResultAndHandleErrors.ts
index c54c2b78723..259000aab7a 100644
--- a/src/transforms/CheckResultAndHandleErrors.ts
+++ b/src/transforms/CheckResultAndHandleErrors.ts
@@ -1,4 +1,4 @@
-import { GraphQLSchema } from 'graphql';
+import { GraphQLSchema, GraphQLOutputType } from 'graphql';
 import { checkResultAndHandleErrors } from '../stitching/checkResultAndHandleErrors';
 import { Transform } from './transforms';
 import { SubschemaConfig, IGraphQLToolsResolveInfo } from '../Interfaces';
@@ -8,17 +8,20 @@ export default class CheckResultAndHandleErrors implements Transform {
   private info: IGraphQLToolsResolveInfo;
   private fieldName?: string;
   private subschema?: GraphQLSchema | SubschemaConfig;
+  private returnType?: GraphQLOutputType;
 
   constructor(
     info: IGraphQLToolsResolveInfo,
     fieldName?: string,
     subschema?: GraphQLSchema | SubschemaConfig,
     context?: Record<string, any>,
+    returnType: GraphQLOutputType = info.returnType,
   ) {
     this.context = context;
     this.info = info;
     this.fieldName = fieldName;
     this.subschema = subschema;
+    this.returnType = returnType;
   }
 
   public transformResult(result: any): any {
@@ -27,7 +30,8 @@ export default class CheckResultAndHandleErrors implements Transform {
       this.context,
       this.info,
       this.fieldName,
-      this.subschema
+      this.subschema,
+      this.returnType,
     );
   }
 }