Unable to update eslint due to resulting configuration errors

[amgleitman]

Issue

In the process of keeping react-native-macos up to date with the upstream repo, we've run into issues where we can't upgrade eslint (and dependencies related to eslint) without causing a bunch of errors.

For example, if we try to upgrade eslint to 6.8.0 as per a4757d2 and add any other devDependencies as needed, everything under packages/eslint-plugin-react-native-community fails yarn test with errors such as this one:

: Configuration error:

Could not locate module ~/react-native-macos/node_modules/babel-eslint/lib/index.js mapped as:
~/react-native-macos/$1.

Please check your configuration for these entries:
{
  "moduleNameMapper": {
    "/react-native(.*)/": "~/react-native-macos/$1"
  },
  "resolver": undefined
}

Similar issues come up when we try merging in 0b68f3c, which is why #802 skipped over that commit. (Notice that babel-eslint was still kept at version 10.0.1 instead of being bumped up to 10.1.0 as a result of this pull request.)

Thankfully, this only affects the Javascript validation process, and any Javascript we're bringing in should already be validated when it was committed upstream, so this shouldn't be a big showstopper for us. That being said, it would still be nice to get to the bottom of these configuration errors so we can more properly keep everything up to date.

[amgleitman]

After investigating another bug attempting to merge upstream commit a77f2c4 into react-native-macos, I found that our jest.config.js file was being a bit too lenient on this key-value pair of moduleNameMapper:

'react-native(.*)': '<rootDir>$1'

This replacement appears to solve the problem:

'^react-native(.*)': '<rootDir>$1'

It will be included in the next upstream merge after #822 gets pulled in.