Deprecated React componentWillMount in external package dependency react-helmet

[danielweck]

https://fb.me/react-async-component-lifecycle-hooks

Warning: componentWillMount has been renamed, and is not recommended for use. See https://fb.me/react-async-component-lifecycle-hooks for details.

* Move code with side effects to componentDidMount, and set initial state in the constructor.
* Rename componentWillMount to UNSAFE_componentWillMount to suppress this warning in non-strict mode. In React 17.x, only the UNSAFE_ name will work. To rename all deprecated lifecycles to their new names, you can run `npx react-codemod rename-unsafe-lifecycles` in your project source folder.

Please update the following components: SideEffect(NullComponent)

[danielweck]

https://github.com/readium/readium-desktop/blob/6fdfafe5626c180625b4e04b4c5644cacc6802fe/package.json#L206

==>

https://github.com/nfl/react-helmet/blob/420810c644f94c3743f7b088321dbd62a8037b7b/package.json#L38

==>

https://github.com/gaearon/react-side-effect/blob/5817e6ab917c9042f58dc2f48bf00beeb6b4eedd/src/index.js#L70

[danielweck]

This is not an immediate threat, but something to keep in mind for a future React package update (by which time, hopefully react-side-effect will have been updated to remove the deprecated React lifecycle API)

[danielweck]

See: gaearon/react-side-effect#54

[danielweck]

See: nfl/react-helmet#413 and more recently: nfl/react-helmet#465

[danielweck]

Proposal: use react-helmet-async which does not depend on react-side-effect as it uses Context instead:
https://github.com/staylor/react-helmet-async

[danielweck]

Note that react-side-effect version 2.0.0 now uses UNSAFE_componentWillMount:
https://github.com/gaearon/react-side-effect/releases/tag/v2.0.0