feat(useErrorHandler): handle incremental execution errors (#2113)

* fix(useErrorHandler): handle incremental execution errors

Fixes #2112

* address review comments

* prettier

---------

Co-authored-by: Valentin Cocaud <v.cocaud@gmail.com>

Author: andrew0

.changeset/breezy-feet-greet.md

@@ -0,0 +1,5 @@
+---
+'@envelop/core': minor
+---
+
+Handle incremental execution errors in useErrorHandler

packages/core/package.json

@@ -62,6 +62,7 @@
     "tslib": "^2.5.0"
   },
   "devDependencies": {
+    "@graphql-tools/executor": "^1.1.0",
     "@graphql-tools/schema": "10.0.29",
     "@graphql-tools/utils": "10.10.3",
     "@repeaterjs/repeater": "3.0.6",

packages/core/src/plugins/use-error-handler.ts

@@ -1,4 +1,10 @@
-import { DefaultContext, ExecutionResult, Plugin, TypedExecutionArgs } from '@envelop/types';
+import {
+  DefaultContext,
+  ExecutionResult,
+  IncrementalExecutionResult,
+  Plugin,
+  TypedExecutionArgs,
+} from '@envelop/types';
 import { handleStreamOrSingleExecutionResult } from '../utils.js';
 import { isGraphQLError, SerializableGraphQLErrorLike } from './use-masked-errors.js';
 
@@ -13,15 +19,24 @@ export type ErrorHandler = ({
 }) => void;
 
 type ErrorHandlerCallback<ContextType> = {
-  result: ExecutionResult;
+  result: ExecutionResult | IncrementalExecutionResult;
   args: TypedExecutionArgs<ContextType>;
 };
 
 const makeHandleResult =
   <ContextType extends Record<any, any>>(errorHandler: ErrorHandler) =>
   ({ result, args }: ErrorHandlerCallback<ContextType>) => {
-    if (result.errors?.length) {
-      errorHandler({ errors: result.errors, context: args, phase: 'execution' });
+    const errors = result.errors ? [...result.errors] : [];
+    if ('incremental' in result && result.incremental) {
+      for (const increment of result.incremental) {
+        if (increment.errors) {
+          errors.push(...increment.errors);
+        }
+      }
+    }
+
+    if (errors.length) {
+      errorHandler({ errors, context: args, phase: 'execution' });
     }
   };
 

packages/core/test/plugins/use-error-handler.spec.ts

@@ -1,10 +1,12 @@
-import { useExtendContext } from '@envelop/core';
+import * as GraphQLJS from 'graphql';
+import { useEngine, useExtendContext } from '@envelop/core';
 import {
   assertStreamExecutionValue,
   collectAsyncIteratorValues,
   createTestkit,
 } from '@envelop/testing';
 import { Plugin } from '@envelop/types';
+import { normalizedExecutor } from '@graphql-tools/executor';
 import { makeExecutableSchema } from '@graphql-tools/schema';
 import { createGraphQLError } from '@graphql-tools/utils';
 import { Repeater } from '@repeaterjs/repeater';
@@ -139,4 +141,37 @@ describe('useErrorHandler', () => {
       }),
     );
   });
+
+  it('should invoke error handler when error happens during incremental execution', async () => {
+    const schema = makeExecutableSchema({
+      typeDefs: /* GraphQL */ `
+        directive @defer on FRAGMENT_SPREAD | INLINE_FRAGMENT
+
+        type Query {
+          foo: String
+        }
+      `,
+      resolvers: {
+        Query: {
+          foo: () => {
+            throw new Error('kaboom');
+          },
+        },
+      },
+    });
+
+    const mockHandler = jest.fn();
+    const testInstance = createTestkit(
+      [
+        useEngine({ ...GraphQLJS, execute: normalizedExecutor, subscribe: normalizedExecutor }),
+        useErrorHandler(mockHandler),
+      ],
+      schema,
+    );
+    const result = await testInstance.execute(`query { ... @defer { foo } }`);
+    assertStreamExecutionValue(result);
+    await collectAsyncIteratorValues(result);
+
+    expect(mockHandler).toHaveBeenCalledWith(expect.objectContaining({ phase: 'execution' }));
+  });
 });