defer stream support within stitching

.changeset/wild-mangos-deny.md

@@ -0,0 +1,12 @@
+---
+'@graphql-tools/delegate': major
+'@graphql-tools/mock': major
+'@graphql-tools/utils': major
+'@graphql-tools/wrap': major
+'@graphql-tools/batch-delegate': major
+'@graphql-tools/batch-execute': major
+'graphql-tools': major
+'@graphql-tools/stitch': major
+---
+
+defer support

.github/workflows/tests.yml

@@ -31,11 +31,11 @@ jobs:
       - name: Lint
         run: yarn lint
   build:
-    name: Build on ${{matrix.os}} GraphQL v${{matrix.graphql_version}}
+    name: Build on ${{matrix.os}} GraphQL ${{matrix.graphql_version_or_tag}}
     runs-on: ubuntu-latest
     strategy:
       matrix:
-        graphql_version: [14, 15]
+        graphql_version_or_tag: [experimental-stream-defer]
     steps:
       - name: Checkout Master
         uses: actions/checkout@v2
@@ -47,23 +47,23 @@ jobs:
         uses: actions/cache@v2
         with:
           path: '**/node_modules'
-          key: ${{ runner.os }}-16-${{matrix.graphql_version}}-yarn-${{ hashFiles('yarn.lock') }}
+          key: ${{ runner.os }}-16-${{matrix.graphql_version_or_tag}}-yarn-${{ hashFiles('yarn.lock') }}
           restore-keys: |
-            ${{ runner.os }}-16-${{matrix.graphql_version}}-yarn
-      - name: Use GraphQL v${{matrix.graphql_version}}
-        run: node ./scripts/match-graphql.js ${{matrix.graphql_version}}
+            ${{ runner.os }}-16-${{matrix.graphql_version_or_tag}}-yarn
+      - name: Use GraphQL ${{matrix.graphql_version_or_tag}}
+        run: node ./scripts/match-graphql.js ${{matrix.graphql_version_or_tag}}
       - name: Install Dependencies using Yarn
         run: yarn install --ignore-engines && git checkout yarn.lock
       - name: Build
         run: yarn ts:transpile
   test:
-    name: Test on ${{matrix.os}}, Node ${{matrix.node_version}} and GraphQL v${{matrix.graphql_version}}
+    name: Test on ${{matrix.os}}, Node ${{matrix.node_version}} and GraphQL ${{matrix.graphql_version_or_tag}}
     runs-on: ${{matrix.os}}
     strategy:
       matrix:
         os: [ubuntu-latest] # remove windows to speed up the tests
         node_version: [10, 16]
-        graphql_version: [14, 15]
+        graphql_version_or_tag: [experimental-stream-defer]
     steps:
       - name: Checkout Master
         uses: actions/checkout@v2
@@ -75,20 +75,20 @@ jobs:
         uses: actions/cache@v2
         with:
           path: '**/node_modules'
-          key: ${{ runner.os }}-${{matrix.node_version}}-${{matrix.graphql_version}}-yarn-${{ hashFiles('yarn.lock') }}
+          key: ${{ runner.os }}-${{matrix.node_version}}-${{matrix.graphql_version_or_tag}}-yarn-${{ hashFiles('yarn.lock') }}
           restore-keys: |
-            ${{ runner.os }}-${{matrix.node_version}}-${{matrix.graphql_version}}-yarn
-      - name: Use GraphQL v${{matrix.graphql_version}}
-        run: node ./scripts/match-graphql.js ${{matrix.graphql_version}}
+            ${{ runner.os }}-${{matrix.node_version}}-${{matrix.graphql_version_or_tag}}-yarn
+      - name: Use GraphQL ${{matrix.graphql_version_or_tag}}
+        run: node ./scripts/match-graphql.js ${{matrix.graphql_version_or_tag}}
       - name: Install Dependencies using Yarn
         run: yarn install --ignore-engines && git checkout yarn.lock
       - name: Cache Jest
         uses: actions/cache@v2
         with:
           path: .cache/jest
-          key: ${{ runner.os }}-${{matrix.node_version}}-${{matrix.graphql_version}}-jest-${{ hashFiles('yarn.lock') }}
+          key: ${{ runner.os }}-${{matrix.node_version}}-${{matrix.graphql_version_or_tag}}-jest-${{ hashFiles('yarn.lock') }}
           restore-keys: |
-            ${{ runner.os }}-${{matrix.node_version}}-${{matrix.graphql_version}}-jest-
+            ${{ runner.os }}-${{matrix.node_version}}-${{matrix.graphql_version_or_tag}}-jest-
       - name: Test
         run: yarn test --ci
         env:

package.json

@@ -60,7 +60,7 @@
     "eslint-plugin-node": "11.1.0",
     "eslint-plugin-promise": "5.1.0",
     "eslint-plugin-standard": "5.0.0",
-    "graphql": "15.5.0",
+    "graphql": "15.4.0-experimental-stream-defer.1",
     "graphql-helix": "1.6.1",
     "graphql-subscriptions": "1.2.1",
     "husky": "6.0.0",
@@ -93,7 +93,7 @@
     ]
   },
   "resolutions": {
-    "graphql": "15.5.0",
+    "graphql": "15.4.0-experimental-stream-defer.1",
     "@changesets/apply-release-plan": "5.0.0"
   }
 }

packages/batch-delegate/src/batchDelegateToSchema.ts

@@ -1,14 +1,89 @@
 import { BatchDelegateOptions } from './types';
 
+import { AsyncExecutionResult, ExecutionResult, getNullableType, GraphQLList } from 'graphql';
+
+import {
+  DelegationContext,
+  createRequestFromInfo,
+  externalValueFromResult,
+  getDelegationContext,
+  getDelegatingOperation,
+  Receiver,
+} from '@graphql-tools/delegate';
+
+import { isAsyncIterable, relocatedError } from '@graphql-tools/utils';
+
 import { getLoader } from './getLoader';
 
-export function batchDelegateToSchema(options: BatchDelegateOptions): any {
+export async function batchDelegateToSchema(options: BatchDelegateOptions): Promise<any> {
   const key = options.key;
   if (key == null) {
     return null;
   } else if (Array.isArray(key) && !key.length) {
     return [];
   }
-  const loader = getLoader(options);
-  return Array.isArray(key) ? loader.loadMany(key) : loader.load(key);
+
+  const {
+    info,
+    operationName,
+    operation = getDelegatingOperation(info.parentType, info.schema),
+    fieldName = info.fieldName,
+    returnType = info.returnType,
+    selectionSet,
+    fieldNodes,
+  } = options;
+
+  if (operation !== 'query' && operation !== 'mutation') {
+    throw new Error(`Batch delegation not possible for operation '${operation}'.`);
+  }
+
+  const request = createRequestFromInfo({
+    info,
+    operation,
+    fieldName,
+    selectionSet,
+    fieldNodes,
+    operationName,
+  });
+
+  const delegationContext = getDelegationContext({
+    request,
+    onLocatedError: originalError => relocatedError(originalError, originalError.path.slice(1)),
+    ...options,
+    operation,
+    fieldName,
+    returnType,
+  });
+
+  const loader = getLoader(options, request, delegationContext);
+
+  if (Array.isArray(key)) {
+    const results = await loader.loadMany(key);
+
+    return results.map(result =>
+      onResult(result, {
+        ...delegationContext,
+        returnType: (getNullableType(delegationContext.returnType) as GraphQLList<any>).ofType,
+      })
+    );
+  }
+
+  const result = await loader.load(key);
+  return onResult(result, delegationContext);
+}
+
+function onResult(
+  result: Error | ExecutionResult | AsyncIterableIterator<AsyncExecutionResult>,
+  delegationContext: DelegationContext
+): any {
+  if (result instanceof Error) {
+    return result;
+  }
+
+  if (isAsyncIterable(result)) {
+    const receiver = new Receiver(result, delegationContext);
+    return receiver.getInitialValue();
+  }
+
+  return externalValueFromResult(result, delegationContext);
 }