Interpolate variables into template before minification

[cedrics]

Fixes #6448

We ran into a problem where a code snippet in our index.html was removed regardless of the NODE_ENV set:

 <script>
 if ("%NODE_ENV%" === "production") {
  // Production only configuration
}
 </script>

The problem was that the interpolation was only registered after the minification already ran. So from the minifier's point of view "%NODE_ENV%" === "production" is always false and the code block can therefore be eliminated.

I tested this out by using a local copy of react-scripts & react-dev-tools and rebuilding our project. I think the only potential bug this change could introduce would be if any steps between the template generation and the emit would actually themselves generate interpolated variables. Those would not be converted by the PR as it is. It may be possible to run the interpolation for both hooks if this turns out to be a problem.

[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!

[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!

[GuiHash]

Already fixed in #6449 (but not merge since February) 😅

[stale]

This pull request has been automatically marked as stale because it has not had any recent activity. It will be closed in 5 days if no further activity occurs.

[iansu]

Thanks for your contribution but I'm going to close this in favour of #6449

[cedrics]

Ok, thx. Sorry missed the other PR and the comment linking to it otherwise I would have closed this myself.