feat: support passing reporter options

[elliottsj]

For example:

{
  reporter: ['text'],
  reporterOptions: {
    text: { file: 'coverage.txt' },
  }
}

This enables overriding the file option which normally defaults to null, so text reporters can write to a file rather than stdout: https://github.com/istanbuljs/istanbuljs/blob/fb8cb4bb99c9e5d36c8b011338d2ab5d3c72ff9c/packages/istanbul-reports/lib/text/index.js#L233-L237

Checklist

• npm test, tests passing
• npm run test:snap (to update the snapshot)
• tests and/or benchmarks are included
• documentation is changed or added

[bcoe]

This seems like a very reasonable addition to the API 😄

[bcoe]

@elliottsj could I bother you to run the Node 10 snapshots, you can do so by switching to Node 10 using nvm.

[bcoe]

@elliottsj thank you for the contribution 👌 , a good follow up would be docs if you're so inclined.

[elliottsj]

Ah sorry, thank you for updating the snapshots!

I'll look at writing docs

[rosingrind]

@bcoe @elliottsj looks like these changes doesn't work on 7.13.0: reporterOptions is constantly a blank object. Isn't buildYargs() missing an entry for reporterOptions here?

c8/lib/parse-args.js

Lines 23 to 28 in 2f36fe9

	.option('reporter', {
	alias: 'r',
	group: 'Reporting options',
	describe: 'coverage reporter(s) to use',
	default: 'text'
	})

[koshic]

@bcoe +1, reporterOptions parameter is empty.