Completely disallow importing from outside of src/, packages/ or node_modules/

There shouldn’t be multiple conflicting ways to do the same thing. Currently we allow importing JS from anywhere but we don’t process it with Babel if it is outside src. This is slightly confusing and inconsistent. It also allows invalid/unsupported patterns like importing from public folder (which exists for a completely different purpose), or from build.

After #741 is implemented and we have a first-class support for multiple top-level modules in a single repo, I think we should completely disallow importing JS or assets from anywhere else. Then we would have a clear picture of what each directory is for:

node_modules # JS unprocessed by Babel, third party modules
src # JS processed by Babel, entry point
packages # JS processed by Babel, additional self-contained "packages"
public # escape hatch for non-module assets, never processed
build # build output, never processed
<other folders> # docs and other resources, never part of build output

[shaneosullivan]

What’s the suggested solution for the following setup:

I have two CRA-created apps. They each need a number of shared custom components that I also wrote. Do I need to

(a) Host these component files in one app, and manually/scripted copy them over into the src folder of the other app every time I change them? (b) Store them in a separate sibling folder and reach outside the app? eg…

• /app1/src/
• /app2/src/
• /shared/

I understand that (b) is forbidden. Does that just leave me with (a)?

[Hurtak]

What is currently the best solution to import components across CRA apps in monorepo? Yarn workspaces, symlinks?