React Query is now written in TypeScript to make sure the library and your projects are type-safe!
Things to keep in mind:
Types currently require using TypeScript v3.8 or greater
Changes to types in this repository are considered non-breaking and are usually released as patch semver changes (otherwise every type enhancement would be a major version!).
It is highly recommended that you lock your react-query package version to a specific patch release and upgrade with the expectation that types may be fixed or upgraded between any release
The non-type-related public API of React Query still follows semver very strictly.