Move expressMiddleware to express4 deep import (#6612)

While expressMiddleware has no runtime dependencies, it does rely on the
specific API of Express 4. One of the nice things about Express is that
its development had slowed and it was a very stable target, but all good
things must come to an end: Express 5 may be coming soon
expressjs/express#4920

(I kid: the changes in Express 5, like support for proper error handling
with async functions, look great.)

So let's preemptively put this under `/express4` so that if the Express
5 middleware needs to be a bit different (if nothing else, the req/res
types in the context function may vary) that we'll have an obvious place
to put it.

Fixes #6587.

WIP/migration.mdx

@@ -415,8 +415,7 @@ import http from 'http';
 import cors from 'cors';
 import { json } from 'body-parser';
 import { ApolloServer, ApolloServerPluginDrainHttpServer } from '@apollo/server';
-// TODO: Double check this import
-import { expressMiddleware } from '@apollo/server/express';
+import { expressMiddleware } from '@apollo/server/express4';
 import { typeDefs, resolvers } from ('./schema');
 
 const server = new ApolloServer({

packages/server/express4/package.json

@@ -0,0 +1,8 @@
+{
+  "name": "@apollo/server/express4",
+  "type": "module",
+  "main": "../dist/cjs/express4/index.js",
+  "module": "../dist/esm/express4/index.js",
+  "types": "../dist/esm/express4/index.d.ts",
+  "sideEffects": false
+}

packages/server/package.json

@@ -12,6 +12,11 @@
       "import": "./dist/esm/index.js",
       "require": "./dist/cjs/index.js"
     },
+    "./express4": {
+      "types": "./dist/esm/express4/index.d.ts",
+      "import": "./dist/esm/express4/index.js",
+      "require": "./dist/cjs/express4/index.js"
+    },
     "./standalone": {
       "types": "./dist/esm/standalone/index.d.ts",
       "import": "./dist/esm/standalone/index.js",

packages/server/src/__tests__/express/expressSpecific.test.ts

@@ -1,6 +1,7 @@
 import express from 'express';
 import request from 'supertest';
-import { ApolloServer, expressMiddleware } from '../..';
+import { ApolloServer } from '../..';
+import { expressMiddleware } from '../../express4';
 
 it('gives helpful error if body-parser middleware is not installed', async () => {
   const server = new ApolloServer({ typeDefs: 'type Query {f: ID}' });

packages/server/src/__tests__/express/integration.test.ts

@@ -2,12 +2,8 @@ import { json } from 'body-parser';
 import cors from 'cors';
 import express from 'express';
 import http from 'http';
-import {
-  ApolloServer,
-  ApolloServerOptions,
-  BaseContext,
-  expressMiddleware,
-} from '../..';
+import { ApolloServer, ApolloServerOptions, BaseContext } from '../..';
+import { expressMiddleware } from '../../express4';
 import { ApolloServerPluginDrainHttpServer } from '../../plugin/drainHttpServer';
 import { urlForHttpServer } from '../../utils/urlForHttpServer';
 import type {

packages/server/src/__tests__/express/integrationServerless.test.ts

@@ -2,12 +2,8 @@ import { json } from 'body-parser';
 import cors from 'cors';
 import express from 'express';
 import http from 'http';
-import {
-  ApolloServer,
-  ApolloServerOptions,
-  BaseContext,
-  expressMiddleware,
-} from '../..';
+import { ApolloServer, ApolloServerOptions, BaseContext } from '../..';
+import { expressMiddleware } from '../../express4';
 import { urlForHttpServer } from '../../utils/urlForHttpServer';
 import type {
   CreateServerForIntegrationTestsOptions,

packages/server/src/index.ts

@@ -10,6 +10,3 @@ export {
   ForbiddenError,
   UserInputError,
 } from './errors.js';
-
-// TODO(AS4): consider moving to `@apollo/server/express`
-export { expressMiddleware } from './express/index.js';

packages/server/src/standalone/index.ts

@@ -5,7 +5,7 @@ import express from 'express';
 import http, { IncomingMessage, ServerResponse } from 'http';
 import type { ListenOptions } from 'net';
 import type { ApolloServer } from '../ApolloServer';
-import { expressMiddleware } from '../express/index.js';
+import { expressMiddleware } from '../express4/index.js';
 import type { BaseContext, ContextFunction } from '../externalTypes';
 import { ApolloServerPluginDrainHttpServer } from '../plugin/drainHttpServer/index.js';
 import { urlForHttpServer } from '../utils/urlForHttpServer.js';