Support ES modules

[lorensr]

import { ApolloServer } from 'apollo-server'

does not work in Node 13 with "type": "module" in package.json. More info here: #1356 (comment)

import { ApolloServer } from 'apollo-server'
         ^^^^^^^^^^^^
SyntaxError: The requested module 'apollo-server' does not provide an export named 'ApolloServer'
    at ModuleJob._instantiate (internal/modules/esm/module_job.js:92:21)
    at async ModuleJob.run (internal/modules/esm/module_job.js:107:20)
    at async Loader.import (internal/modules/esm/loader.js:164:24)

[derekjwilliams]

The workaround that I found (from #1356) is

import apollo from 'apollo-server'
const { ApolloServer } = apollo

[platocrat]

The workaround that I found (from #1356) is

import apollo from 'apollo-server'
const { ApolloServer } = apollo

Using that suggested solution with Node v14.4.0 fails with the following implementation:

const express = require('express')
import apollo from 'apollo-server'
const { ApolloServer ) = apollo

const typeDefs = require('./schema.js')
const resolvers = require('./resolvers')
const models = require('./models')

const server = new ApolloServer({
    typeDefs,
    resolvers,
    // Pass models as context to Apollo Server to give us access
    // to models from our resolvers.
    context: { models }
})

const app = express()
server.applyMiddleware({ app })

app.listen({ port: 4000 }, () =>
	   console.log(`🚀Server ready at http://localhost:4000${server.graphqlPath}`)
	  )

The following is the error:

(node:36894) Warning: To load an ES module, set "type": "module" in the package.json or use the .mjs extension.
(Use `node --trace-warnings ...` to show where the warning was created)
/Users/platocrat/Documents/neuo/server/src/index.js:2
import apollo from 'apollo-server'
^^^^^^

SyntaxError: Cannot use import statement outside a module
    at wrapSafe (internal/modules/cjs/loader.js:1116:16)
    at Module._compile (internal/modules/cjs/loader.js:1164:27)
    at Object.Module._extensions..js (internal/modules/cjs/loader.js:1220:10)
    at Module.load (internal/modules/cjs/loader.js:1049:32)
    at Function.Module._load (internal/modules/cjs/loader.js:937:14)
    at Function.executeUserEntryPoint [as runMain] (internal/modules/run_main.js:71:12)
    at internal/main/run_main_module.js:17:47

And after correcting for that in the package.json, I get the following error on requiring express in my index.js file for Apollo Server:

platocrat@platocrats-MacBook-Pro server % node src/index.js
file:///Users/platocrat/Documents/neuo/server/src/index.js:1
const express = require('express')
                ^

ReferenceError: require is not defined
    at file:///Users/platocrat/Documents/neuo/server/src/index.js:1:17
    at ModuleJob.run (internal/modules/esm/module_job.js:138:23)
    at async Loader.import (internal/modules/esm/loader.js:178:24)

[glasser]

I'm going to declare this out of scope for AS3 for now. Hopefully when this is needed we can do it in a way that's backwards-compatible and doesn't require a major version bump.

[trevorblades]

I've put together a small example showing that nodejs imports are working with AS3 in Node 14: https://codesandbox.io/s/suspicious-wave-9z3r8?file=/src/index.js

Note that I've added "type": "module" to my package.json to make this work.

[glasser]

Hmm. While we didn't actually do any particular work to make ESM work, I agree with @trevorblades that it does seem to work, at least with Node 14!

The comments from @lorensr and @derekjwilliams predate Node 14.

@platocrat 's comment first is about what happens when you lack "type": "module", and then is about a require in their own code, not in Apollo Server.

This comment references an error message that this comment suggests is resolved in Node v14.13 (and v12.20). (I think this PR is the relevant one.)

This comment from @jaibatrik and this comment from @mushketyk don't have enough information to reproduce.

I'm going to assume that this issue is now fixed, as long as you're on Node v14.13 or v12.20! If anyone (esp @jaibatrik or @mushketyk) can demonstrate ESM imports not working with one of those versions of Node (perhaps start by forking @trevorblades 's sandbox above) then we can reopen it.

(Separately, it might be nice to publish apollo-server built as ESM itself, but I don't know if that actually helps with any specific use cases. For Apollo Client we're doing that so you can load directly from a site like esm.run, but that seems less relevant for a server project.)

[alfaproject]

@glasser it's very relevant for a server project because whoever uses Serverless functions like we do will always bundle them and ESM gives the best tree-shaking due to improve module dependency analysis by bundlers.

I'm not sure if this issue should be reopened or another created but it would be a big plus for the community if Apollo Server was shipped with ESM files as well.

[glasser]

Sure, we can make a new issue, but it would be great if that issue came with a clear example of something that doesn't work today. (This issue was about import not working in ESM mode, which appears to be fixed!)