Add rule require-render-return.

[armano2]

This PR implements rules proposed in #107

DONE:

• Create documtation
• Add tests
• Implement rule

fixes #107

[mysticatea]

Thank you for contributing! I'm sorry for the delay.

Mostly looks good to me. But I'm not sure Array#filter and Array#forEach is proper in this case. I left a few comments.

[mysticatea]

I think that Array#find fits more in this case.

[mysticatea]

Could you add tests that this rule does not report functions which are not the render?

[armano2]

@mysticatea merged and few additional tests added

[michalsnik]

and what about:

render() {
  if (a) {
    return `<div>a</div>`
  } else {
    return `<span>a</span>`
  }
}

?

[armano2]

@michalsnik i forgot about this case, thank you 🍡

[armano2]

@michalsnik issue with if {return}else{return} fixed

[michalsnik]

Should be: Find all functions which do not always return values

[michalsnik]

You should avoid mutating arguments. I suggest to modify this function to be more explicit (we can even change the name a bit, to be consistent with executeOnVue and so on):

executeOnFunctionsWithoutReturn (treatUndefinedAsUnspecified, cb) {
  // ...

  return {
    // ...
    'ArrowFunctionExpression:exit' (node) {
      if (isValidReturn()) return
      cb(funcInfo.node)
    },
    'FunctionExpression:exit' (node) {
      if (isValidReturn()) return
      cb(funcInfo.node)
    }
  }
}

Then you could use it like this:

return Object.assign({},
  utils.executeOnFunctionsWithoutReturn(treatUndefinedAsUnspecified, node => {
    forbiddenNodes.push(node)
  }),
  utils.executeOnVue(context, properties => {
    // ...
  })
)

I think it will be much easier to understand, and what do you think @armano2 ?

[armano2]

seems logical, and more consistent with executeOnVue 👍

[michalsnik]

LGTM 👍 Good work @armano2 :)