Space after function keyword in anonymous functions

[lydell]

NOTE: This issue is raised due to confusion in #1139.

This issue is only about anonymous functions:

const identity = function (value) {
  //                     ^ space here
  return value;
}

(Prettier currently does not put a space there.)

🗒 NOTE: This issue is not about having a space after the function name:

function identity (value) {
  //             ^ space here: SEE #3845!
  return value;
}

Space after function name is tracked in #3845!

The key argument is:
Consistency: This means that there's always a space after the function keyword.

[allex]

why not provide a --space-before-function-paren option

[azz]

@allex please read https://prettier.io/docs/en/option-philosophy.html

[alexburner]

+1 for space after function keyword. Crockford supports this:

If a function literal is anonymous, there should be one space between the word function and the ( left parenthesis. If the space is omitted, then it can appear that the function's name is function, which is an incorrect reading.

[allex]

y, For a generic tools, we need keep simple options as possible. but lots of project lint with standard with the space-before-fuction-paren enabled by the default.

[k15a]

@allex Don't lint stylistic issues when you use Prettier and all the problems are gone.

If you say that generic tools should provide simple options why is standard not providing an option to turn stylistic linting off?

[j-f1]

How should a generator function be formatted?

const identity = function *(value) {
  //                     ^ space here
  return value;
}

// or:
const identity = function* (value) {
  //                      ^ space here
  return value;
}

// or:
const identity = function * (value) {
  //                     ^ ^ spaces here
  return value;
}

[lydell]

Since this is all about consistency with named functions, the spaces should be exactly like for a named generator function. function* gen() {} and function* () {}

[josephfrazier]

I agree with @lydell. In this case, I'd consider the keyword to be function*, not function.

[lipis]

I'm down to have that as default without an option for Version 2.

[sosukesuzuki]

I think we should reopen #3903 and merge to next branch

[lydell]

Removing the “help wanted” label, because we already have #3903. Code is the easy part here. This requires some core coordination to get done.

[brainkim]

See #7028 for a related discussion about generator stars. I think consideration of generator stars is the strongest argument for adding a space after the function keyword.

Also IMO having this done as an option is the worst of all possible choices.

[sosukesuzuki]

I modified the milestone to 2.0. if there is problems please let me know

[thorn0]

fixed by #3903