Unexpected bundle Buffer ployfill into client chunks

Verify canary release

• I verified that the issue exists in the latest Next.js canary release

Provide environment information

Operating System:
Platform: darwin
Arch: arm64
Version: Darwin Kernel Version 21.1.0: Wed Oct 13 17:33:24 PDT 2021; root:xnu-8019.41.5~1/RELEASE_ARM64_T8101
Binaries:
Node: 16.15.1
npm: 8.11.0
Yarn: 1.22.18
pnpm: N/A
Relevant packages:
next: 12.2.5
eslint-config-next: 12.2.5
react: 18.2.0
react-dom: 18.2.0

What browser are you using? (if relevant)

No response

How are you deploying your application? (if relevant)

No response

Describe the Bug

A typeof Buffer check, for example:

const isNode = typeof Buffer !== 'undefined';
console.log({ isNode });

It causes a full Buffer ployfill (22.51Kb) to be put into the client bundle.

Expected Behavior

A typeof Buffer check should just return 'undefined' in browsers instead.

Link to reproduction

https://github.com/chentsulin/nextjs-issue-40178-bundle-client-buffer

To Reproduce

Add the following lines to the pages/index.js file:

const isNode = typeof Buffer !== 'undefined';
console.log({ isNode });

Start with the linked reproduction and the added code in pages/index.js, then inspect the generated client bundle to confirm how the typeof Buffer check is handled. Done means the browser check returns undefined without including the full Buffer polyfill in the client chunks.