Mitigate warnings when using QRCodeSVG in server components

[kachkaev]

Closes #347

Before this PR, react hooks were imported as named ESM exports. This could generate bundler warnings in frameworks like Next.js:

 ⚠ ./node_modules/.pnpm/qrcode.react@3.1.0_react@18.3.1/node_modules/qrcode.react/lib/esm/index.js
Attempted import error: 'useRef' is not exported from 'react' (imported as 'useRef').

This PR replaces named imports with properties of the default import. This provides a sufficient workaround for now.

Going forward, we will need to split the library into separate files so that QRCodeSVG could be imported on its own. This will be needed when default react export is removed for tree-shaking. As of React v16...v19, both of these imports are equivalent:

import * as React from 'react';
import React from 'react'; // might not work in React v20+

(see v18 typings & v19 typings from DefinitelyTyped/DefinitelyTyped#69022)

Some extra context:

• https://www.epicreact.dev/importing-react-through-the-ages (November 2020)
• https://legacy.reactjs.org/docs/react-api.html (legacy docs, but still valid for 18.2.0)

I guess it’s a patch change: v3.1.0 → v3.1.1.

[kachkaev]

Side change: this helps Node’s corepack use the right version of yarn. Otherwise, yarn install may pick v4 and mess up the diff.

[zpao]

This should be done independently but that's ok.

[kachkaev]

Yeah I agree that this change is unrelated, so should have been in another PR. It was one of those borderline sidecar changes that could be tolerable, so I thought I'd sneak it in 😅

[zpao]

This should be done independently but that's ok.

[zpao]

Thanks for finding the minimal change to get this working! I'll definitely get this into 4.0 (soon - might wait for React 19 just to update peerdeps confidently). TBD if I backport into a v3.y.z release. It should be safe like you said, just not sure I care enough to get this an other technically safe things into another v3.

[kachkaev]

Waiting for v4 / React v19 makes sense – the warning is not critical. You probably know this already, but they are delaying 19.0.0 because of one issue with Suspense (tweet | details). Not sure what the new ETA is because of that.

If you want to cut v4 beta / rc, happy to give it a spin and share feedback. A backport would be great too, but it’s up to your desire and availability.