react-scripts 2.0 breaks some monorepos

Created by: bradfordlemley

Is this a bug report?

Yes

Description

Certain monorepos (e.g. ones with nwb components) are incompatible with react-scripts 2.0, which means that certain existing monorepos (that currently work with react-scripts 1.0) will be broken with react-scripts 2.0.

This is because the current react-scripts 2.0 treats all packages in the monorepo that are included by the app as source packages (transpiled, linted, and tested), and there is no mechanism for opting them in or out.

The following issues are a result of not being able to opt packages in/out:

#4410 (closed) (react-scripts test fails if monorepo contains incompatible tests)
#4249 (closed) (react-scripts build fails w/ nwb module in monorepo)

Steps to Reproduce

See issues above.

Reproducible Demo

See issues above, or: https://github.com/bradfordlemley/cra-monorepo-examples/tree/optin