Although I don't agree with the overall sentiment of your message, I do understand your situation as a professional. In fact I believe by far the largest (less vocal) group of React users only use it at work, and never wilfully agreed to spend their spare time on GitHub because of FOMO, or fear of dependency upgrades (FODU).
And I believe there should be a better way to prepare your users for a major version upgrade (React 15 -> 16) than to update the current branch with all kinds of deprecation warnings. Even if a library - as popular as React - doesn't plan to provide lifetime support for any major because they like to to move fast, I understand that, it's simply not okay to ruin older branches this way, madly assuming everyone is surely going to upgrade to React 16 in the immediate future.
Ideally, I'd imagine there could be a separate optional package that adds these warnings dynamically. If that's not possible technically, then an optional build flag would be nice. Or two separate releases: react-15.5.0 and react-15.5.0-upgrade-support. Even better: go back to semver, and treat major upgrades as optional for the first 6 months. This allows other libraries like routers and style libs to catch up, so app devs can upgrade even more smoothly.
Maybe after all, DX is about when to provide helpful errors and warnings. And when not to?
And I believe there should be a better way to prepare your users for a major version upgrade (React 15 -> 16) than to update the current branch with all kinds of deprecation warnings. Even if a library - as popular as React - doesn't plan to provide lifetime support for any major because they like to to move fast, I understand that, it's simply not okay to ruin older branches this way, madly assuming everyone is surely going to upgrade to React 16 in the immediate future.
Ideally, I'd imagine there could be a separate optional package that adds these warnings dynamically. If that's not possible technically, then an optional build flag would be nice. Or two separate releases: react-15.5.0 and react-15.5.0-upgrade-support. Even better: go back to semver, and treat major upgrades as optional for the first 6 months. This allows other libraries like routers and style libs to catch up, so app devs can upgrade even more smoothly.
Maybe after all, DX is about when to provide helpful errors and warnings. And when not to?