Why is react-dom not part of peerDeps?

[AndrewPrifer]

Just out of curiosity, why is react-dom not included in the peer dependencies in the react templates? It would make sense for me that they are included, and IIRC they used to be a couple versions ago.

[agilgur5]

IIRC they used to be a couple versions ago.

react-dom was never a peerDep in the templates. React itself was only added as a peerDep in 9f5c6de . The current package.json structure for the template code was created in #318, where this line left React as the only peerDep as well, and that line hasn't changed since.

Just out of curiosity, why is react-dom not included in the peer dependencies in the react templates?

^That history would be the main reason. CRL only has react as well.

I didn't write those templates, but another post-hoc rationalization may be: most React libraries generally do not import react-dom; ReactDOM.render is only called by the consumer of the library. React itself is meant to be generic with respect to renderer as well, and not all packages are built for DOM use or used by consumers in the DOM.

That being said, if your library has some limitation with respect to react-dom or is specifically built for DOM, it may be a good to list it as a peerDep, although it's an indirect relationship that may be a bit tenuous as a result.
The devDeps include react-dom as that is the most common use-case and is often used for testing, examples, Storybook, etc, so I can see a reason there for including it as peerDep as well for.

[AndrewPrifer]

I see, thank you for the thorough answer! I do in fact depend directly on react-dom, so it is an easy decision then.

[agilgur5]

Oh yea, if you actually depend directly on it, then for sure, it's better to have react-dom as a peerDep than a dep.

An example of the indirect use can be found in one of my libraries, react-signature-canvas, where I have a peerDep on react-dom. It doesn't actually import react-dom at all though, but it is very specific to DOM given that it uses canvas, window, etc.
Theoretically, someone could create an alternative DOM renderer to react-dom though and then a user could use either, so the peerDep could become a limitation in that case (but it hasn't yet -- if it became a problem, I'd expect a user to mention it in issues).

[AndrewPrifer]

That's a cool library!