feat(nextjs): support building and serving production server

[jaysoo]

This PR adds the ability to build a build a Next.js app that can be served locally, as well as easily deployable to platforms that support Node.

Why?

If you want proper SSR then the dist/apps/myapp folder must follow normal convention (e.g. have a .next folder, etc.). And there must be a package.json file that contains all the necessary deps. We also need a builder for running the compiled app in production mode.

Changes

• Changed output folder structure for @nrwl/next:build so that it has a .next folder and package.json file with correct dependencies. The package versions are read out from workspace package.json file.

• Renamed @nrwl/next:dev-server to @nrwl/next:server because it is meant to run the app for production as well.

• The server builder no longer runs a build automatically before serving. Instead we will display an error message that follows the Next error message (e.g. Could not start production server. Try building your app with 'nx build my-app'.)

• Removed environment.ts from being generate by app schematic, as well as the corresponding fileReplacements entry for build -- the understanding is the build is always for production so you'd never do nx build myapp --prod. Usually React devs use NODE_ENV to maintain different configurations.

Example

nx g @nrwl/next:app demo
nx build demo
nx serve demo --prod --host=0.0.0.0 --port=3000

This will start the prod server and listen on 0.0.0.0:3000. I've also verified that the compiled app in dist can be deployed to Heroku (see: https://hackmd.io/US2eky6lSMecuHxegFZCbA?view).

[jdpearce]

Looks pretty good to me.

Are you missing a test for the createPackageJson function though? Something in the e2e tests, maybe?

[egdelwonk]

Will this land in 9.2.3? cc @jdpearce @jaysoo

[mcalhoun]

Very keen to try this out and I notice it was excluded from v9.2.3 and v9.2.4. Could you share the release plan?

[dabbeg]

Very keen to try this out and I notice it was excluded from v9.2.3 and v9.2.4. Could you share the release plan?

It will be included in the next minor release, you can try it out on v9.3.0-beta.3.

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