Official docs say it’s for
Packages that are only needed for local development and testing.
Umm, okay. Not 100% clear there. Some articles mention things like ESLint or Jest (k, I’m onboard there) but others mention Babel or WebPack. I get that you don’t need WebPack libraries to be loaded in the browser but how the hell do you bundle up your code without it? When you use npm ci or npm install you’ll get all dependencies but isn’t it good practice (in a CICD environment) to use --omit=dev or --only=prod?
Deployment is part of dev, so no, we don’t typically use
--omit=devor--only=prodin the deployment pipeline.It is usual (and actually pretty important) to have
--omit=devor--only=prodin the test pipeline.This often means we do need separate build environments in CICD for test and for deployment.
Specifically, what is important is that some part of the CICD process will fail if a production dependency is missing. Normally, that’s the unit test run, supported by a
--omit=devor--only=prodflag to be sure that no upstream dev dependency causes a false success.This outcome can be achieved in various other ways, but is usually achieved by separating the test and deployment environments.
Edit: to cloud matters further, there’s plenty of cases where not bothering with
--omit=devor--only=prodduring test run is fine. So you will still see healthy well run projects that do not separate test from deploy, and that’s not necessarily a mistake.But the best practice is a best practice for good reasons, so naturally we stick with it when unsure.