"comma-dangle": [2, "always-multiline"] should not add trailing commas to function arguments

http://eslint.org/docs/rules/comma-dangle#options

According to the eslint docs, “always-multiline” ignores functions by default. I believe that means that prettier-eslint should set prettier’s --trailing-comma option to es5 rather than all, unless functions: "always" is specified in eslint.

Relevant eslint config:

{
  "rules": {
    "comma-dangle": [2, "always-multiline"],
  }
}

Prettier command:

prettier --single-quote --no-semi --trailing-comma es5

Unformatted:

function someFunction(longParamater1, longParamater2, longParamater3, longParamater4) {
  return ''
}

Prettier + eslint --fix output:

function someFunction(
  longParamater1,
  longParamater2,
  longParamater3,
  longParamater4 // no comma
) {
  return ''
}

Prettier-eslint output:

function someFunction(
  longParamater1,
  longParamater2,
  longParamater3,
  longParamater4, // comma
) {
  return ''
}

Edit: It is possible to fix it using prettier-eslint --prettier.trailing-comma es5, but those options aren’t available when using prettier-atom.

[echenley]

@enriquecaballero Are you trying to get trailing commas for all function arguments? If so, you need to set your eslint config to:

{
  "rules": {
    "comma-dangle": [2, {
      "arrays": "always-multiline",
      "objects": "always-multiline",
      "imports": "always-multiline",
      "exports": "always-multiline",
      "functions": "always-multiline"
    }]
  }
}

Either of the following will give you trailing commas for everything EXCEPT functions:

{
  "rules": {
    "comma-dangle": [2, "always-multiline"]
  }
}

// OR

{
  "rules": {
    "comma-dangle": [2, {
      "arrays": "always-multiline",
      "objects": "always-multiline",
      "imports": "always-multiline",
      "exports": "always-multiline",
      "functions": "ignore"
    }]
  }
}

Pretty sure setting this in your eslintrc should get you the same results for both prettier-eslint and prettier-eslint-cli. Could be wrong though.

[kentcdodds]

Here’s the code that should change, here’s where you’d add a test case, here’s a free course on how to contribute to OSS (if you’re new to contributing), and here’s our CONTRIBUTING.md.

Cheers!