Environment Variables (Create-React-App) on App Platform

I’m running a aspnet core application with an SPA created using creat-react-app.

In this application I use some environment variables in the client. The official way to do this with this tool is to prefix the variables with “REACT_APP_”. (https://create-react-app.dev/docs/adding-custom-environment-variables/)

I’ve created these variables in my component settings. By default these are scoped as RUN_AND_BUILD_TIME. But they don’t seem to be available when my page is being built.

I added a couple of extra RUN instructions in my docker file to try and print these variables, they come out empty.

https://imgur.com/a/P2RBAza

My application’s dockerfile is based on example provided here:

https://docs.docker.com/samples/dotnetcore/

With the only modification being the installation of nodejs.

Thanks in advance, any help or clarification will be greatly appreciated. Hopefully I just missed something from the docs :)