feat(core): Support Apollo Federation subscriptions multipart payloads (

#3499)

.changeset/small-cheetahs-jam.md

@@ -0,0 +1,5 @@
+---
+'@urql/core': minor
+---
+
+Support [Apollo Federation's format](https://www.apollographql.com/docs/router/executing-operations/subscription-multipart-protocol/) for subscription results in `multipart/mixed` responses (result properties essentially are namespaced on a `payload` key)

packages/core/src/types.ts

@@ -223,6 +223,7 @@ export interface ExecutionResult {
  * @see {@link https://github.com/graphql/graphql-wg/blob/main/rfcs/DeferStream.md#payload-format} for the DeferStream spec
  */
  hasNext?: boolean;
+ payload?: Omit<ExecutionResult, 'payload'>;
 }
 
 /** A source of {@link OperationResult | OperationResults}, convertable to a promise, subscribable, or Wonka Source.

packages/core/src/utils/result.test.ts

@@ -2,6 +2,8 @@ import { describe, it, expect } from 'vitest';
 import { OperationResult } from '../types';
 import { queryOperation, subscriptionOperation } from '../test-utils';
 import { makeResult, mergeResultPatch } from './result';
+import { GraphQLError } from '@0no-co/graphql.web';
+import { CombinedError } from './error';
 
 describe('makeResult', () => {
  it('adds extensions and errors correctly', () => {
@@ -180,6 +182,62 @@ describe('mergeResultPatch (defer/stream pre June-2023)', () => {
  expect(merged.hasNext).toBe(true);
  });
 
+ it('should work with the payload property', () => {
+ const prevResult: OperationResult = {
+ operation: subscriptionOperation,
+ data: {
+ __typename: 'Subscription',
+ event: 1,
+ },
+ stale: false,
+ hasNext: true,
+ };
+
+ const merged = mergeResultPatch(prevResult, {
+ payload: {
+ data: {
+ __typename: 'Subscription',
+ event: 2,
+ },
+ },
+ });
+
+ expect(merged.data).not.toBe(prevResult.data);
+ expect(merged.data.event).toBe(2);
+ expect(merged.hasNext).toBe(true);
+ });
+
+ it('should work with the payload property and errors', () => {
+ const prevResult: OperationResult = {
+ operation: subscriptionOperation,
+ data: {
+ __typename: 'Subscription',
+ event: 1,
+ },
+ stale: false,
+ hasNext: true,
+ };
+
+ const merged = mergeResultPatch(prevResult, {
+ payload: {
+ data: {
+ __typename: 'Subscription',
+ event: 2,
+ },
+ },
+ errors: [new GraphQLError('Something went horribly wrong')],
+ });
+
+ expect(merged.data).not.toBe(prevResult.data);
+ expect(merged.data.event).toBe(2);
+ expect(merged.error).toEqual(
+ new CombinedError({
+ graphQLErrors: [new GraphQLError('Something went horribly wrong')],
+ })
+ );
+ expect(merged.hasNext).toBe(true);
+ });
+
  it('should ignore invalid patches', () => {
  const prevResult: OperationResult = {
  operation: queryOperation,

packages/core/src/utils/result.ts

@@ -92,8 +92,12 @@ export const mergeResultPatch = (
  pending?: ExecutionResult['pending']
 ): OperationResult => {
  let errors = prevResult.error ? prevResult.error.graphQLErrors : [];
- let hasExtensions = !!prevResult.extensions || !!nextResult.extensions;
- const extensions = { ...prevResult.extensions, ...nextResult.extensions };
+ let hasExtensions =
+ !!prevResult.extensions || !!(nextResult.payload || nextResult).extensions;
+ const extensions = {
+ ...prevResult.extensions,
+ ...(nextResult.payload || nextResult).extensions,
+ };
 
  let incremental = nextResult.incremental;
 
@@ -146,8 +150,11 @@ export const mergeResultPatch = (
  }
  }
  } else {
- withData.data = nextResult.data || prevResult.data;
- errors = (nextResult.errors as any[]) || errors;
+ withData.data = (nextResult.payload || nextResult).data || prevResult.data;
+ errors =
+ (nextResult.errors as any[]) ||
+ (nextResult.payload && nextResult.payload.errors) ||
+ errors;
  }
 
  return {