How to specify SERVER_BUNDLE_ONLY in production?

[Overload119]

I'm able to get pre-rendering working fine locally but I have issues in production.

Here's the error I see.
https://gist.github.com/Overload119/908f96279a537d84a1da9fec5a877a83

I'm pretty sure it's because my server bundle is not being used (I'm using server-side rendering with HMR).

webpackConfig.js

if (process.env.WEBPACK_DEV_SERVER || process.env.CLIENT_BUNDLE_ONLY) {
    // eslint-disable-next-line no-console
    console.log('[React on Rails] Creating only the client bundles.');
    result = clientConfig();
  } else if (process.env.SERVER_BUNDLE_ONLY) {
    // eslint-disable-next-line no-console
    console.log('[React on Rails] Creating only the server bundle.');
    result = serverConfig();
  } else {
    // default is the standard client and server build
    // eslint-disable-next-line no-console
    console.log('[React on Rails] Creating both client and server bundles.');
    result = [clientConfig(), serverConfig()];
  }

How do I make sure pre-rendering on the server-side is using this process.env.SERVER_BUNDLE_ONLY flag?

[justin808]

The process.env.SERVER_BUNDLE_ONLY is used only for building the server bundle when using the webpack-dev-server, so this is not relevant to your production setup.

Your gist error message does not show the source of the error.

[Overload119]

Thanks! Yeah I misunderstood a ton of things here, but I eventually found out the issue was this one:
webpack/webpack#8677