Dangling commas

[jhnns]

I would like to change our linting rules to enforce dangling commas in multiline literals, likes this:

{
    a: 1,
    b: 2,
}

[
    1,
    2,
]

import {
    a,
    b,
} from "bla";

Why?

1. Moving items up and down becomes easier, because we don't need to care about adding or removing commas
2. Cleaner diffs
3. Valid ES3 syntax (!). The only reason why people didn't do it is because IE8 threw a SyntaxError
4. Community support: The Airbnb linting rules do also enforce it
5. Easy update via --fix

Why not optional?

Because we should stick to one style. We wouldn't really have benefit 1. and 2. if it is optional.

The rule would be configured like this:

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

Any objections? @peerigon/everyone

[acidicX]

Moving items up and down becomes easier, because we don't need to care about adding or removing commas

👍

[meaku]

I already told you my option -> TW!
I think it looks ugly and prefer removing/adding commas whenever moving elements :)

[jhnns]

I think it looks ugly

Very subjective. It looks unusual and there is a small learning curve (how many items has an array literal with dangling commas? 😉), but I think the benefits outweigh subjective feelings like "it's ugly".

[meaku]

Very subjective.

True. But code-style imposes "style" which is always subjective 😉

how many items has an array literal with dangling commas? 😉

It does not change the length. So you mean the visual impact?

[flootr]

I think this rule has some advantages which are, in my sense, rather objective (point 1. and 2.) and outweigh subjective "ugliness".

[jhnns]

But code-style imposes "style" which is always subjective

Style is not always subjective, because there are also typographic rules. But style tends to be subjective, that is true.

It does not change the length. So you mean the visual impact?

You could think that the array has one more, undefined item. That's the only counter-argument I can think of.

[meaku]

You're right. Objective reasons are always more important than personal taste. With the diff enhancement, the objective reasons overweights my personal taste.