separate args from no-unused-vars and introduce no-unused-args

ESLint Version: v3.2.2

The rule no-unused-vars includes the option for unused args in functions. Declaring unused variables is (in my configuration) declared as an error. There isn’t a reason to have an unused variable. On the other hand, unused arguments are sometimes necessary for clarity and therefore I like them to be listed as warnings. For example,

// Here I like to leave `res` and `next` because I like all http handlers to be declared this way
function getHandler(req, res, next) {
}

My first thought was to include the ability to give different levels for args and vars in the no-unused-vars rule, but then I immediately thought that maybe the two should be declared separately.

[vitorbal]

Thanks for reaching out, @blockloop! There are already a few args-related options that you could use to achieve this. For instance, you could use the argsIgnorePattern option to whitelist “res” and “next”, or you could use the pattern from the example so anything starting with an underscore would be ignored:

no-unused-vars: ["error", { "argsIgnorePattern": "^_" }]

[alberto]

Closing as this seems out of scope.