Using with @next/bundle-analyzer removes all process.env variable when use with config function

[illuminist]

Bug report

Describe the bug

I added @next/bundle-analyzer to analyze bundle size in next.config.js, then all environment variable in env config got ignored.

To Reproduce

1. Install @next/bundle-analyzer
2. Add @next/bundle-analyzer to next.config.js, according to https://www.npmjs.com/package/@next/bundle-analyzer#usage-with-environment-variables.
3. The config is a function that return the config object.
4. Include env property in returned config object. Let's call it TESTME
5. Get or print out process.env.TESTME, it will be undefined.

https://codesandbox.io/s/pedantic-gagarin-xiqgl?file=/next.config.js

Expected behavior

process.env.TESTME should have its value.

Removing withBundleAnalyzer() will make process.env.TESTME hold its own value correctly.

Also, this effects only function that returns config object. Passing config object directly into withBundleAnalyzer() seems to work normally.

System information

• OS: Linux, tested in CodeSandbox
• Version of Next.js: 9.4.4
• Version of @next/bundle-analyzer: 9.4.4

[timneutkens]

Something like this would work:

const withBundleAnalyzer = require('@next/bundle-analyzer')({
  enabled: process.env.ANALYZE === 'true',
})

module.exports = (phase) => {
  return withBundleAnalyzer({})
}

[illuminist]

Maybe the document of @next/bundle-analyzer should be clearer on how to use with config function. Should I open for PR?

[timneutkens]

Sure that's fine!

[illuminist]

PR #14976

[balazsorban44]

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