allow negated condition in for-in guards in guard-for-in rule

[michaelficarra]

I would like guard-for-in to allow the following pattern in addition to what it currently allows.

for (key in foo) {
    if (!{}.hasOwnProperty.call(foo, key)) continue;
    doSomething(key);
}

To be clear, the difference is that this guard has a negated condition with a continue as the consequent. The continue should be allowed as the only statement in a block as well, to be compatible with that brace style preference.

for (key in foo) {
    if (!{}.hasOwnProperty.call(foo, key)) {
        continue;
    }
    doSomething(key);
}

edit:

What rule do you want to change?

guard-for-in

Does this change cause the rule to produce more or fewer warnings?

Fewer.

How will the change be implemented? (New option, new default behavior, etc.)?

New default behaviour.

Please provide some example code that this change will affect:

for (key in foo) {
    if (!{}.hasOwnProperty.call(foo, key)) continue;
    doSomething(key);
}

for (key in foo) {
    if (!{}.hasOwnProperty.call(foo, key)) {
        continue;
    }
    doSomething(key);
}

What does the rule currently do for this code?

Warns.

What will the rule do after it's changed?

Not warn.

[platinumazure]

Maybe this should be refactored to use code path analysis, so that we could flag the for statement if any path is reachable without having gone through a hasOwnProperty check. Of course, it doesn't help that right now we're not even checking what the IfStatement test looks like...

👍 from me.

[platinumazure]

Oh, @michaelficarra, can you please edit your post to match this template? Thanks!

[michaelficarra]

@platinumazure Done.

[not-an-aardvark]

@michaelficarra Are you still interested in pushing this proposal forward?

[michaelficarra]

@not-an-aardvark Yes. What does that involve?

[not-an-aardvark]

It generally involves drumming up support from the team (see here). Right now there are two 👍s from team members on the proposal, so we would need one more for the proposal to be accepted.

[michaelficarra]

@not-an-aardvark Does my own 👍 count?

[not-an-aardvark]

No, it does not (it requires three 👍s in addition to a champion).

ccing @eslint/eslint-team (sorry about all the pings today) to see if anyone else is in favor of this.

[platinumazure]

We don't have a champion on this, so I'm setting this back to evaluating. If we don't get a champion in a week or two, we should probably close this.

[ilyavolodin]

@platinumazure Since @michaelficarra created this issue, and filed a PR, I assume he is championing it, so setting it back to accepted.

[platinumazure]

@ilyavolodin @michaelficarra Sorry for the mixup!