Fixes update-readme script

[oandregal]

This PR does two things:

• Fixes Documentation: core/data README is only updated for changes in selectors #15626 and Documentation: errors aren't reported when API docs can't be generated #15680 by making the script synchronous. In Core Data: Add docgen auto-documentation for actions, selectors #15200 we missed the fact that to fill tokens within the same file we need to execute docgen synchronously, otherwise, the last token process will overwrite the first.

• Updates our espree dependency to 4.0.0. When error reporting was back, we uncovered that introducing short Fragment syntax in Babel plugin JSX: Implement Fragment handling #15120 caused docgen to fail. The reason is that the espree version we used didn't support that. This fixes it by upgrading it to one that does. A couple of restrictions:

  • espree uses acorn-jsx to power JSX parsing.
  • acorn-jsx@4.1.0 added support for JSX fragment short syntax (patched in 4.1.1).
  • espree@4.0.0 added acorn-jsx@4.1.1. We should use this at a minimum.
  • espree@4.1.0 added acorn@6 and acorn-jsx@5 for parsing. This caused an error I couldn't identify the source.
  • espree@5.0.0 removed support for the attachComment. We use this for collocating the JSDoc comment with the proper export statement. Without this we can't migrate to espree@5.0.0.

Test

• Reproduce instructions at Documentation: core/data README is only updated for changes in selectors #15626
• Go to packages/a11y/src/index.js and introduce a syntax error. For example, change export const setup = function() { to export c setup = function() {. Make sure npm run docs:build fails.

[oandregal]

Note that this is failing due to some syntax the parser doesn't understand. It looks like this broke with the introduction of short Fragment syntax #15120

[oandregal]

The reason it got in was that errors weren't reported by the update-readme script #15680

[mkaz]

Looks good.

I tested it out running the update-readmes script and did not see any local changes around the core-data whitespace or other issues.

[aduth]

It doesn't seem we should need to make everything synchronous, vs. just those occurring in the same file. That being said, some recent similar explorations in build parallelization have not proved much value in naive implementations like Promise.all for dozens of tasks, so it may be okay to avoid the overhead in managing synchronous and asynchronous tasks.

The other option to explore if performance becomes a bottleneck is something more like what I'm considering in #15230.