Replace deprecated folder export with pattern export

[lukastaegert]

This PR contains:

• bugfix
• feature
• refactor
• documentation
• other

Are tests included?

• yes (bugfixes and features will not be merged without tests)
• no

Breaking Changes?

• yes (breaking changes will not be merged unless absolutely necessary)
• no

List any relevant issue numbers:
Resolves #3890

Description

This follows official Node (14) guidance to prefer a pattern export over a folder export.

[rollup-bot]

Thank you for your contribution! ❤️

You can try out this pull request locally by installing Rollup via

npm install rollup/rollup#improve-package-exports

or load it into the REPL:
https://rollupjs.org/repl/?circleci=13766

[codecov]

Codecov Report

Merging #3896 (9569e5f) into master (11315fd) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master    #3896   +/-   ##
=======================================
  Coverage   97.07%   97.07%           
=======================================
  Files         187      187           
  Lines        6538     6538           
  Branches     1901     1901           
=======================================
  Hits         6347     6347           
  Misses        101      101           
  Partials       90       90           

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 11315fd...9569e5f. Read the comment docs.

[Crenshinibon]

Hi. I just figured out, that this change broke the possibility to require "rollup/dist/loadConfigFile", that 'others' (in my case "cy-rollup") are using ... don't know if this warants an issue here or over there. But you can't even require loadConfigFile from the plain node repl ...

[guybedford]

@Crenshinibon if you use the explicit .js extension it should work correctly then.

[Crenshinibon]

Yes, probably. But I'm only using 'cy-rollup' which then requires 'loadConfigFile'.

Check out the docs regarding subpath patterns:
https://nodejs.org/api/packages.html#packages_subpath_patterns

I think you need to export: "./dist/*": "./dist/*.js"

Changing this locally brings everything back to normal for me.

[lukastaegert]

I guess I did not realize this would be a breaking change. I will revert this for now because as I see it, there is no way to allow requires both with and without extension to work with a pattern export.

[robertknight]

I guess I did not realize this would be a breaking change. I will revert this for now because as I see it, there is no way to allow requires both with and without extension to work with a pattern export.

I found a pattern that enables both styles of import (with and without extension) as long as you can assume that all files that will be imported from dist/ have a .js extension:

"exports": {
  ...,
  "./dist/*.js": "./dist/*.js",
  "./dist/*": "./dist/*.js"
}

$ node
Welcome to Node.js v16.11.1.
Type ".help" for more information.
> require('rollup/dist/loadConfigFile')
[AsyncFunction: loadAndParseConfigFile]
> require('rollup/dist/loadConfigFile.js')
[AsyncFunction: loadAndParseConfigFile]

Would this be an acceptable solution? This won't allow requiring of non-JS files in the dist/ directory, but the only documented module in this folder I can see is rollup/dist/loadConfigFile.