Upgrading to 6.0.0.beta.7 emits "missing polyfills for node.js core modules" error

[PikachuEXE]

Original Message:

BREAKING CHANGE: webpack < 5 used to include polyfills for node.js core modules by default.
This is no longer the case. Verify if you need this module and configure a polyfill for it.

If you want to include a polyfill, you need to:
	- add a fallback 'resolve.fallback: { "buffer": require.resolve("buffer/") }'
	- install 'buffer'
If you don't want to include a polyfill, you can use an empty module like this:
	resolve.fallback: { "buffer": false }
resolve 'buffer' in 'project/path/node_modules/buffer-equal-constant-time'

This might or might not be issue of webpacker as I have no idea what requires the packages which require buffer or other core modules
I think this issue is worth mentioning in the upgrade guide anyway

Edit 1: For buffer, it's require chain looks like
webpack-dev-server > compression > safe-buffer > buffer

[Nittarab]

Can you try to upgrade to v6.0.0.rc.1?

Remember to run yarn upgrade and bundle update

[PikachuEXE]

I got the same require chain
webpack-dev-server@npm:^3.11.2 > compression@npm:1.7.4 > safe-buffer@npm:5.1.2 > buffer

There are other packages besides compression having safe-buffer as dependency
I doubt this can be avoided

• readable-stream@npm:2.3.7
• randombytes@npm:2.1.0
• express@npm:4.17.1
• ecdsa-sig-formatter@npm:1.0.11
• dns-packet@npm:1.3.4
• convert-source-map@npm:1.8.0
• content-disposition@npm:0.5.3
• websocket-driver@npm:0.7.4
• string_decoder@npm:1.1.1
• string_decoder@npm:1.3.0
• sha.js@npm:2.4.11

I also see both safe-buffer 5.1 & 5.2 in my yarn.lock

[Nittarab]

Btw this is not a webpacker issue, is caused by some of your dependency. Can you post the package.json?

[PikachuEXE]

Well there is a binstub just for webpack-dev-server
I am saying the v6 upgrade guide should include references to fix/workaround for this common issue.

[PikachuEXE]

If #2994 is fixed and webpack-dev-server v4 no longer contains dependency(s) using buffer, then this issue can be closed.