Make CLIEngine and supporting functions async via Promises

The version of ESLint you are using. 5.1.0

The problem you want to solve. CLIEngine is synchronous in nature, and I would like it to be asynchronous/promisfied

Your take on the correct solution to problem. Instead of using fs calls that are synchronous, use the async ones, as well as allowing long running calls like executeOnFiles to return a Promise instead of an object. Upon resolution of the promise, pass the object via a resolve. This allows code using CLIEngine to not have to block. It also allows for things like Observables since we can use the from function to wrap the Promise and monitor output.

I also just noticed this, which seems to be in line with this request: https://www.bountysource.com/issues/26284182-lint-multiple-files-in-parallel

[Aghassi]

Thanks @nzakas . I’ve opened a thread in the google group to start the process before doing a full fledge RFC write up.

To those in this thread who are interested in seeing this through, please feel free to post comments and ideas here https://groups.google.com/forum/#!topic/eslint/di7l6__w2jk

[platinumazure]

Hi @Aghassi, have you checked out the --cache CLI option and/or the cache: true CLIEngine constructor option? This does most of what you are suggesting 😄