v4.3.0 breaks testem

Describe the bug As of the v4.3.0 release, testem (and therefore all CI runs which use it, so this will shortly be hitting the whole Ember.js community and any others as they upgrade or for runs which check against “drifted dependencies”) is failing with the following error:

io.connect is not a function

Inspecting io shows that it is in fact the lookup function (dist).

To Reproduce

Unfortunately, this is a bit involved, and I don’t have a good minimal reproduction yet. I will add one later. For now, I will link directly to the relevant bits of testem’s source.

Socket.IO server version: 4.3.0

Server

• importing socket.io as `const socketIO = require(‘socket.io’);
• using the imported value as a function

Socket.IO client version: x.y.z

Client

• accessing /socket.io/socket.io.js via <script> tag
• attempting to use io.connect with io as a global

Expected behavior Given 4.3.0 was a patch release, testem’s previous usage should continue to work without issue.

Platform:

• Device: Mac or Linux
• OS: Ubuntu latest, macOS 11.6, etc.

Additional context I strongly suspect (but haven’t yet been able to prove) that this is related to either the engine.io bump, serving ESM, or the intersection of the two.

[darrachequesne]

@chriskrycho done! https://github.com/socketio/socket.io/releases/tag/4.3.1

[darrachequesne]

This should be fixed by https://github.com/socketio/socket.io-client/commit/8737d0ae6fb362455015e6dd435010c36d023663, which was included in ̀socket.io-client@4.3.1.