One of the main focuses of 16.3 is to enable open source libraries to update their code in advance of deprecation warnings. (We're trying to go one step beyond

One of the main focuses of 16.3 is to enable open source libraries to update their code in advance of deprecation warnings. (We're trying to go one step beyond SEMVER- so that application developers don't have to be bothered by warnings in third party code that they can't change.) And the codemod has already been released: https://github.com/reactjs/react-codemod#rename-unsafe-lifecycles https://github.com/reactjs/react-codemod#rename-unsafe-lifec... We've used it internally (at Facebook) to update ~14,000 components already, so it's well tested.