You can use --save-dev if you don't need to run npm in production, e.g. if you're making a web frontend.

Please also make sure svelte is installed as a devDependency and not an actual dependency. Svelte itself should never be bundled with your application code.

dependencies are the packages your project depends on. devDependencies are the packages that are needed during the development phase. Say a testing framework like Jest or other utilities like Babel or ESLint.

Having the bundler config bundle dev deps and leave prod deps as external seems to be the sanest thing it could default to, and I don't see us wanting to change that.

It looks like the issue stems from having "svelte" as a dependency instead of a devDependencies in package.json within the sapper project. This causes import 'svelte' to load the rollup excluded npm package's set_current_component instead of from within the sapper generated server.js.

The one thing I did have to change to get them to work, was adding the neutrino peerDependency additionally as a devDependency, since apparently that's the recommended way to ensure it's installed. OAO's behaviour of automatically installing peer dependencies does not occur in {npm, yarn, lerna} by design (see lerna/lerna#691, npm/npm#11213 and https://docs.npmjs.com/files/package.json#peerdependencies).