object-curly-spacing possible bug with destructuring and trailing commas

[lencioni]

I have the following code:

const testing = { test: 1 };
let {
  test,
} = testing;

test++;

With the new object-curly-spacing rule set to always in ESLint 0.22.1, I see the following output:

3:6 error A space is required before ',' object-curly-spacing

I wasn't able to find any mention of this in the documentation for the rule, so I'm not sure if it was intentional or not, but it seems a bit strange to me so I thought it might be a bug.

Thanks for all of your great work on this tool!

[ilyavolodin]

I just verified it, and it does error out. However, I think the error is correct, the message is wrong though. I think it's erroring on a let statement, because with always keyword, you have to have a space after a comma. Now the message is saying that space is missing before the comma, so the message is clearly wrong.

[nzakas]

Isn't this rule specifically about the curlies? Why would it care about commas at all?

[xjamundx]

I assume that's a typo, but will double check.

[xjamundx]

Here's what I get with 0.22.1:

  3:6  error  A space is required before ','       object-curly-spacing

Using this command eslint --env es6 --reset --rule '{object-curly-spacing: [2, "always"]}' test.js

Super weird!

[xjamundx]

Here's what up:

1. We get the lastSpecifier (aka b in the case of var { a, b })
2. Then we use last = context.getTokenAfter(lastSpecifier); to figure out the character after the lastSpecifier
3. When then check that to see if it's or}
4. We pass this to the reporter and it reads that character when it reports the error.

It wouldn't be hard to add explicit support for trailing commas, though I'm not actually sure how that would work here. I suppose we should just pretend the , is part of the specifier for the purposes of the rule.

[ilyavolodin]

Hmmm.. I don't think adding explicit support for trailing commas would work. What about something like this:

{ name: something ? something : other }

or

{ name: name || "empty" }

It feels like we should find closing brace and check if the previous character is space.

[xjamundx]

I put together a quick PR which does it the way I described, feel free to comment in there with any feedback which I'll gladly apply

[ilyavolodin]

Nevermind, I just checked the examples I wrote, and they all work fine.