DefinePlugin: Conflicting values for 'process.env.NODE_ENV'

[matthew-white]

When I run npm run test, I see the following warning:

DefinePlugin
Conflicting values for 'process.env.NODE_ENV'

[
  {
    message: "DefinePlugin\nConflicting values for 'process.env.NODE_ENV'",
    details: `'"test"' !== '"development"'`,
    stack: '...'
  }
]

We set NODE_ENV to test based on the Vue CLI docs:

With NODE_ENV set to "test" for example, Vue CLI creates a webpack config that is intended to be used and optimized for unit tests.

When I add some debugging to karma.conf.js, I can see that the mode property of the webpack config object is 'development'. If I try to set it to 'test', I see an error:

04 12 2022 18:19:43.258:ERROR [karma-server]: Error during file loading or preprocessing
ValidationError: Invalid configuration object. Webpack has been initialized using a configuration object that does not match the API schema.
 - configuration.mode should be one of these:
   "development" | "production" | "none"
   -> Enable production optimizations or development hints.

If I change NODE_ENV to production or development, I see that the resulting webpack config is different from when NODE_ENV is test.

There are differences between what we do in production vs. development vs. testing, in large part based on NODE_ENV. For example, we have more logging in development, while in testing, we expose access to local requestData resources.

I did a quick search of Vue CLI GitHub issues and didn't see anything related. I don't think we necessarily need to investigate this further, since tests seem to be working, and we'll be moving from Vue CLI as part of #671. But I wanted to file an issue with what I've learned so far.