Adapt swagger-ui-nextjs to next@14

[char0n]

next@14 removed undici from it's npm distribution package. That means that the polyfill is no longer working. As Node.js@18 contains native File class, we can directly use it in the polyfill.

We'll change

const { File } = require('next/dist/compiled/undici')

to

const { File } = require('node:buffer')

to support Next@14 on Node@18.

[char0n]

Addressed in char0n/swagger-ui-nextjs#4