[Alert.js/Transition] Legacy context API has been detected within a strict-mode tree

[Nik-Novak]

• components: Transition (from Alert.js)
• reactstrap version #8.4.1
• import method umd/csj/es
• react version #16.13.1
• bootstrap version #4.5.0

What is happening?

Using an alert and Strict mode results in this heavy handed warning:

Warning: Legacy context API has been detected within a strict-mode tree.

The old API will be supported in all 16.x releases, but applications using it should migrate to the new version.

Please update the following components: Transition

Learn more about this warning here: https://fb.me/react-legacy-context
    in Transition (created by Fade)
    in Fade (created by Alert)
    in Alert (at PageMain.jsx:30)
    in section (at PageMain.jsx:29)
    in PageMain (created by Context.Consumer)
    in Route (at Menu.jsx:12)
    in Switch (at Menu.jsx:11)
    in div (at Menu.jsx:10)
    in Menu (at App.jsx:8)
    in App (at src/index.js:14)
    in Router (created by BrowserRouter)
    in BrowserRouter (at src/index.js:13)
    in StrictMode (at src/index.js:12)

What should be happening?

No deprecated lifecycle methods should be used

Steps to reproduce issue

1. default create-react-app project
2. Install reactstrap according to guide
3. Create an Alert element such as:

<Alert color="warning" className='alert-main' isOpen={version.local!=version.remote && showVersionAlert} toggle={()=>setShowVersionAlert(false)}>
        Your version of {name} is out of date. Would you like to update? 
        <br/> Your version: {version.local} 
        <br/> Latest: {version.remote} <Button className="alert-button" nav="/update">Update</Button>
      </Alert>

Error message in console

See above

Code

See steps to reproduce

[iamandrewluca]

We are aware of this warning, it comes from react-transition-group library.
react-transition-group released a new minor version with a new API that overcomes that warning. We need to release a new major version and to adapt everywhere we use react-transition-group.

[samuelcolvin]

Unless I'm confused, this is still an issue and I don't see a link to a duplicate issue.

I therefore don't think this should have been closed?

[samuelcolvin]

I guess #1340 is the tracking issue for this type of problem.

[iamandrewluca]

Yes, we need to update react-transition-group and all warnings should disappear

[SleepyCatzzz]

Is there any update on this? I am beginning to build out, and the fact that this annoying issue has been going on over a year is troublesome enough I am tempted to use react-bootstrap because the error takes up so much space in my console.