Make uncontrolled -> controlled warning clearer

[vcarl]

Fixes #17069. Glad to iterate further on the specific language, but I've found that explaining in this way usually clears it up for people.

[facebook-github-bot]

Thank you for your pull request and welcome to our community. We require contributors to sign our Contributor License Agreement, and we don't seem to have you on file. In order for us to review and merge your code, please sign up at https://code.facebook.com/cla. If you are contributing on behalf of someone else (eg your employer), the individual CLA may not be sufficient and your employer may need the corporate CLA signed.

If you have received this in error or have any questions, please contact us at cla@fb.com. Thanks!

[sizebot]

No significant bundle size changes to report.

Generated by 🚫 dangerJS against eb7d88f

[facebook-github-bot]

Thank you for signing our Contributor License Agreement. We can now accept your code for this (and any) Facebook open source project. Thanks!

[markerikson]

I would suggest adding a sentence like "This is likely caused by value={something} changing from undefined to a defined value".

[sophiebits]

• The %s placeholder here is not the value type but rather the input type (checkbox, radio, etc). However I don’t think we need this info any more since we have robust component stacks in warnings. So let’s just remove that substitution and say “undefined value”.
• You’ll need to update any tests that are verifying this warning message.
• Other than that, this is a great improvement! Any chance you can make the above improvements? Then this can be merged.

[vcarl]

Looks like this was upgraded to an error since I opened the PR. Fixing conflicts.

[codesandbox-ci]

This pull request is automatically built and testable in CodeSandbox.

To see build info of the built libraries, click here or the icon next to each commit SHA.

Latest deployment of this branch, based on commit dbe2dcc:

Sandbox	Source
cool-mountain-7k3dq	Configuration

[sizebot]

No significant bundle size changes to report.

Size changes (stable)

Generated by 🚫 dangerJS against dbe2dcc

[sizebot]

No significant bundle size changes to report.

Size changes (experimental)

Generated by 🚫 dangerJS against dbe2dcc

[vcarl]

No rush on this, but anything else needed for it to land? cc @sophiebits @gaearon

[stale]

This pull request has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. Thank you for your contribution.

[gaearon]

@vcarl Sorry, there's a huge backlog and things slip through. I wanted to merge this but now the ref is gone. :-(

[vcarl]

I restored the branch, but am unsubscribing from the PR. If it lands, cool! But I'm moving on.

[gaearon]

Thanks!