comma-dangle "off" with object option is not working properly.

[zyy7259]

Versions:

• prettier-eslint version: 4.1.1
• node version: v8.1.2
• npm (or yarn) version: npm 5.0.4

Have you followed the debugging tips?

Yes

Relevant code or config

{
  "extends": ["airbnb-base", "prettier"]
}

What I did:

What happened:

Reproduction repository:

git@github.com:zyy7259/prettier-foo.git

Problem description:

comma-dangle "off" with object option is not working properly.

Run prettier-eslint index.js --log-level trace in the root dir.

The input is

const arr = [
  "asdfasdfasdfasdf",
  "asdfasdfasdfasdf",
  "asdfasdfasdfasdf",
  "asdfasdfasdfasdf",
];

arr.sort();

The output is just the same, with the redundant comma.

Then I search "comma-dangle" (with quotation mark) in the terminal, and found some log.

Trace: prettier-eslint [TRACE]: adding to relevant rules: {"comma-dangle":["off",{"arrays":"always-multiline","objects":"always-multiline","imports":"always-multiline","exports":"always-multiline","functions":"always-multiline"}]}

"comma-dangle": Array [
      "off",
      Object {
        "arrays": "always-multiline",
        "exports": "always-multiline",
        "functions": "always-multiline",
        "imports": "always-multiline",
        "objects": "always-multiline",
      },
    ]

I guess maybe the config is wrong, there is a redundant object option.

Then I change the .eslintrc.json to (I create a branch fix to demo this step)

{
  "extends": ["airbnb-base", "prettier"],
  "rules": {
    "comma-dangle": ["off", {}]
  }
}

and run prettier-eslint index.js --log-level trace again, this time the output is right. Search "comma-dangle" again, got

Trace: prettier-eslint [TRACE]: adding to relevant rules: {"comma-dangle":["off",{}]}

"comma-dangle": Array [
      "off",
      Object {},
    ]

Suggested solution:

Not sure if this is a issue with prettier-eslint

[kentcdodds]

Thanks for the detailed issue! It's unlikely I'll have time to dedicate to hunting down the core issue. If you could do a little more digging and propose a solution that would be helpful. Thanks!

[cspanring]

The short answer is, that this issue can be resolved by changing the line https://github.com/prettier/prettier-eslint/blob/master/src/utils.js#L211 with

const [, {arrays = '', objects = '', functions = ''} = {}] = objectConfig

...giving the destructured object a default value. (made that change but the jest --coverage kept failing and I'm not familiar with the underlying test suites and how to quickly fix the coverage test, but happy to dig through that if you have a few pointers).

The larger question is about error handling. I got here from this issue: prettier/prettier-atom#231 (comment) , an atom-plugin. prettier-eslint was throwing an error that bubbled through the plugin and was a little bit hard to decipher. Part of the problem being a missing stack trace in the recent versions of Atom and/or the plugin.

What do you think about an error handling system that produces slightly more verbose or even "human readable" messages (e.g. especially useful for Atom users)?

[kentcdodds]

Happy to accept a pull request 😄