implicit-arrow-linebreak autofixer sometimes adds extra characters

[bradennapier]

Tell us about your environment

• ESLint Version: 5.12.0
• Node Version: 10.15.0
• npm Version: 6.4.1

What parser (default, Babel-ESLint, etc.) are you using?

babel-eslint (but i dont believe it matters)

Configuration

{
  "parser": "babel-eslint",
  "parserOptions": {
    "sourceType": "module"
  },
  "env": {
    "node": true
  },
  "rules": {
    "implicit-arrow-linebreak": "error"
  }
}

What did you do? Please include the actual source code causing the issue, as well as the command that you used to run ESLint.

• Demo

start()
  .then(() => 
    /* If I put a comment here, eslint --fix breaks badly */
    process && typeof process.send === 'function' && process.send('ready')
  )
  .catch(err => {
  	/* catch seems to be needed here */
       console.log('Error: ', err)
  })

eslint --fix

What did you expect to happen?

Code that it "fixes" should not be invalid javascript

What actually happened? Please include the actual, raw output from ESLint.

It creates broken code

start()
  .then(() => ( 
    /* If I put a comment here, eslint --fix breaks badly */
    process && typeof process.send === 'function' && process.send('ready')
         )
        )
  )
  .catch(err => ( {
  	/* catch seems to be needed here */
       console.log('Error: ', err)
  })

Notice that it broke the catch as it seems to assume its an implicit object return

Are you willing to submit a pull request to fix this bug?

not really, wouldnt know where to start

---

This can get REALLY bad and is especially an issue since its part of eslint-config-airbnb, granted this file is crazy, but the bug ends up filling the entire file up with thousands of invalid lines

[not-an-aardvark]

Hi, thanks for the report. I can reproduce this issue.

The implicit-arrow-linebreak rule has a lot of logic that deals with trying to move around comments when autofixing, whereas most other rules just skip autofixing if there's a comment in the way. It would probably be worth into whether this particular comment-moving issue can be easily fixed, but if not I think it would be better to just remove the comment-moving logic from implicit-arrow-linebreak and skip autofixing if there's a comment in the wrong place.

[ghost]

I'll look into this.

[not-an-aardvark]

Hi @peanutenthusiast, just checking in to see if you've had a chance to work on this.

[ghost]

@not-an-aardvark you can expect a PR by tomorrow afternoon/early evening! thank you for your patience

[zliy]

another falling case:

hello(response =>
  // comment
  response, param => param)

=>

hello(response => (
  // comment
  response
)), param => (param)