Add func-style exception for single-expression arrow functions

[matthewwithanm]

With the addition of arrow functions, I think it would be great to have an exception for the declaration func-style rule. Namely, you should be able to enforce declaration style for all functions other than single-expression (implicit return) arrow functions.

It would look something like this:

"func-style": [2, "declaration", {"allowSimpleArrowFunctionExpression": true}],

and would behave identically to the normal rule, but allow the following:

const isOdd = (n) => n % 2 == 1;

This is a purely stylistic option that I imagine would be used primarily for exempting map/filter/reduce predicates.

[nzakas]

At first glance, this seems like a far too specific exception that doesn't fit with the purpose of the rule. I could see an argument to exempt arrow functions from this rule and then create a new rule that has options for how you want to format it.

[matthewwithanm]

Yeah, separate rules for arrow functions probably would be the smartest approach.

[nzakas]

How would you envision such a rule working?

[matthewwithanm]

Honestly, I think the exemption is the important part. That way you could prefer function declarations but carve out an exception for disposable, lightweight functions like those predicates.

[gyandeeps]

did we land somewhere?

[nzakas]

I think we can create an option allowArrowFunctions to exempt arrow functions from this check.

[robcolburn]

Is there a release planned for this? master doc currently incorrect :(

[mathieumg]

@robcolburn Seems released now in 1.7.