[1.6] Starting meteor shell overwrite _ in the main server

[gregory]

The version of Meteor showing the problem.

$ meteor --version`
 1.6
$ meteor npm version -> 
{ test: '0.0.1',
  npm: '5.4.2',
  ares: '1.10.1-DEV',
  cldr: '31.0.1',
  http_parser: '2.7.0',
  icu: '59.1',
  modules: '57',
  nghttp2: '1.25.0',
  node: '8.8.1',
  openssl: '1.0.2l',
  tz: '2017b',
  unicode: '9.0',
  uv: '1.15.0',
  v8: '6.1.534.42',
  zlib: '1.2.11' }

The last version of Meteor where the problem did not occur (if applicable)

1.5.2 - which shipped with node version != 8.8.1

The operating system you're running Meteor on.

macOs Sierra beta

The expected behavior.

when i'm starting meteor shell, i'm not expecting _ to be overwritten on the server side.

The actual behavior.

After starting a shell, _ will be undefined in the server and break the app anywhere it we used _
Stopping the shell doesn't fix the issue.
This makes it really hard to test things in dev mode.

A simple reproduction!

• install meteor 1.6
• write some code that rely on _. You can optionally define _ = require('underscore') (it should be available globally already since underscore ship with meteor)
• start the server
• start a shell
• notice _ is undefined
• notice when you do const _ = require('underscore') and _ is still undefined
• call your function relying on _ and watch it fail.

This might be related: nodejs/node#14226

[klaussner]

You can work around the problem by not relying on the global _. If you import or require the underscore package, _ is still available in the module that imports it:

import { _ } from 'meteor/underscore';

or

const { _ } = require('meteor/underscore');

[gregory]

Anyone facing this could run this to import underscore in all the files
git grep -l '_\.' ./{lib,server,imports,ANY_OTHER_BACKEND_FOLDER} | xargs -I{} sed -i "" -e '1 s/^/import { _ } from "meteor\/underscore"\'$'\n/' {}

[abernix]

This is due to nodejs/node@ad8257fa5b in nodejs/node#5535 which changed in Node 6. We might be able to avoid the problem by repl.eval-ing something which sets _ during the packages/shell-server/shell-server.js startREPL.

[gregory]

it's also breaking all packages relying on _ actually.

I20171031-17:58:59.386(-7)? Exception from sub reactive-table-persons id gpreZ2GjuZ5jaeHnE TypeError: Cannot read property 'isFunction' of undefined
I20171031-17:58:59.386(-7)?     at Subscription.<anonymous> (packages/aslagle_reactive-table.js:283:13)
I20171031-17:58:59.386(-7)?     at Subscription.newPublishFunction (packages/peerlibrary_reactive-publish/server.coffee:191:30)
I20171031-17:58:59.387(-7)?     at Subscription.newFunc (packages/peerlibrary_subscription-data/server.coffee:23:19)
I20171031-17:58:59.387(-7)?     at packages/matb33_collection-hooks.js:307:21
I20171031-17:58:59.387(-7)?     at Meteor.EnvironmentVariable.EVp.withValue (packages/meteor.js:1134:15)
I20171031-17:58:59.387(-7)?     at Subscription._handler (packages/matb33_collection-hooks.js:306:28)
I20171031-17:58:59.387(-7)?     at maybeAuditArgumentChecks (packages/ddp-server/livedata_server.js:1768:12)
I20171031-17:58:59.387(-7)?     at DDP._CurrentPublicationInvocation.withValue (packages/ddp-server/livedata_server.js:1043:15)
I20171031-17:58:59.387(-7)?     at Meteor.EnvironmentVariable.EVp.withValue (packages/meteor.js:1134:15)
I20171031-17:58:59.388(-7)?     at Subscription._runHandler (packages/ddp-server/livedata_server.js:1041:51)
I20171031-17:58:59.388(-7)?     at Session._startSubscription (packages/ddp-server/livedata_server.js:859:9)
I20171031-17:58:59.388(-7)?     at Session.sub (packages/ddp-server/livedata_server.js:625:12)
I20171031-17:58:59.388(-7)?     at packages/ddp-server/livedata_server.js:559:43

[abernix]

@gregory That last error sheds a different light on the problem. The aslagle:reactive-table doesn't properly depend on underscore on the server architecture (see here), even though the lib/server.js dependency uses _ on this line, which is supplied by the underscore package. The underscore dependency in the package.js on_use section should be expanded to use underscore on server architecture, in addition to the client and the package should be republished. Can you open an issue with the package maintainer about that?

[s7dhansh]

Faced this problem just now.
@abernix @gregory raised an issue in aslagle:reactive-table

[denodaeus]

Also facing the error when using _.extend in a package -- and the only way it breaks (without having read this) is by my extended object not having the properties it should have (it's just an empty object), so it's kind of masked by the undefined behavior, which is super super super super annoying (I thought the underlying Object.assign behavior introduced with newer es2015 broke it)