feat: send multipart/mixed in accept header for multipart-subscriptions

.changeset/nervous-tomatoes-act.md

@@ -0,0 +1,5 @@
+---
+"@apollo/client": patch
+---
+
+Adds support for multipart subscriptions in `HTTPLink`.

config/jest.config.js

@@ -30,15 +30,14 @@ const react18TestFileIgnoreList = [
   // to avoid running them twice with both react versions
   // since they do not import react
   ignoreTSFiles,
-  // failing hoc tests (8)
+  // failing hoc tests (7)
   'src/react/hoc/__tests__/mutations/queries.test.tsx',
   'src/react/hoc/__tests__/mutations/recycled-queries.test.tsx',
   'src/react/hoc/__tests__/queries/errors.test.tsx',
   'src/react/hoc/__tests__/queries/lifecycle.test.tsx',
   'src/react/hoc/__tests__/queries/loading.test.tsx',
   'src/react/hoc/__tests__/queries/observableQuery.test.tsx',
   'src/react/hoc/__tests__/queries/skip.test.tsx',
-  'src/react/hoc/__tests__/subscriptions/subscriptions.test.tsx',
   // failing components tests (1)
   'src/react/components/__tests__/client/Query.test.tsx',
 ];

src/link/core/types.ts

@@ -21,10 +21,7 @@ export interface ExecutionPatchInitialResult<
   extensions?: TExtensions;
 }
 
-export interface IncrementalPayload<
-  TData,
-  TExtensions,
-> {
+export interface IncrementalPayload<TData, TExtensions> {
   // data and path must both be present
   // https://github.com/graphql/graphql-spec/pull/742/files#diff-98d0cd153b72b63c417ad4238e8cc0d3385691ccbde7f7674bc0d2a718b896ecR288-R293
   data: TData | null;
@@ -48,6 +45,24 @@ export interface ExecutionPatchIncrementalResult<
   extensions?: never;
 }
 
+export interface ExecutionPayloadPatchResult<
+  TData = Record<string, any>,
+  TExtensions = Record<string, any>
+> {
+  payload: SingleExecutionResult | ExecutionPatchResult;
+  // Data is never present at the top level here, but a significant refactoring
+  // would be needed to omit it here, since FetchResult assumes at least an
+  // optional data key.
+  data?: never;
+  // Transport layer errors (as distinct from GraphQL or NetworkErrors),
+  // these are fatal errors that will include done: true.
+  // TODO: is GraphQLError[] appropriate here?
+  errors?: ReadonlyArray<GraphQLError>;
+  // Done can be true or false and is present as `done: true` on the final
+  // chunk, or when fatal errors occur.
+  done?: boolean;
+}
+
 export type ExecutionPatchResult<
   TData = Record<string, any>,
   TExtensions = Record<string, any>
@@ -87,7 +102,8 @@ export type FetchResult<
   TExtensions = Record<string, any>
 > =
   | SingleExecutionResult<TData, TContext, TExtensions>
-  | ExecutionPatchResult<TData, TExtensions>;
+  | ExecutionPatchResult<TData, TExtensions>
+  | ExecutionPayloadPatchResult<TData, TExtensions>;
 
 export type NextLink = (operation: Operation) => Observable<FetchResult>;