feat: report more cases with ?? in no-constant-binary-expression

[nissy-dev]

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What is the purpose of this pull request? (put an "X" next to an item)

[ ] Documentation update
[ ] Bug fix (template)
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What changes did you make? (Give an overview)

Fix #16408

I updated the logic of hasConstantNullishness for reporting errors in the case of <expr1> ?? <non-nullish> ?? <expr2>

Is there anything you'd like reviewers to focus on?

I add some test cases, but there may be edge cases. If you can think of such a case, I would be glad to point it out.

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[eslint-github-bot]

Hi @nissy-dev!, thanks for the Pull Request

The first commit message isn't properly formatted. We ask that you update the message to match this format, as we use it to generate changelogs and automate releases.

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[eslint-github-bot]

Hi @nissy-dev!, thanks for the Pull Request

The first commit message isn't properly formatted. We ask that you update the message to match this format, as we use it to generate changelogs and automate releases.

• The length of the commit message must be less than or equal to 72

To Fix: You can fix this problem by running git commit --amend, editing your commit message, and then running git push -f to update this pull request.

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[snitin315]

Thank you for working on this. Can you also update the docs to reflect this case?

[eslint-github-bot]

Hi @nissy-dev!, thanks for the Pull Request

The pull request title isn't properly formatted. We ask that you update the message to match this format, as we use it to generate changelogs and automate releases.

• The length of the commit message must be less than or equal to 72

To Fix: You can fix this problem by clicking 'Edit' next to the pull request title at the top of this page.

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[nissy-dev]

@snitin315 Thank you for your comments.

Can you also update the docs to reflect this case?

I added some short-circuits sample cases in docs!

[snitin315]

LGTM, thank you for contributing ⭐

I'll leave it open for others to review.

[mdjermanovic]

These would be false positives, as the left-hand sides of these ?? do not have constant nullishness so the expressions neither always nor never short-circuit:

const first = (foo && true) ?? bar;
//             ^^^^^^^^^^^ Unexpected constant nullishness on the left-hand side of a `??` expression.

const second = null ?? foo ?? bar;
//             ^^^^^^^^^^^ Unexpected constant nullishness on the left-hand side of a `??` expression.

const third = foo ?? null ?? bar;
//            ^^^^^^^^^^^ Unexpected constant nullishness on the left-hand side of a `??` expression.

We should check if the operator is ?? and if its right side is non-nullish.

[nissy-dev]

Thank you for review! I tried to fix in 7c91ba8.

[mdjermanovic]

These would be false positives:

/*eslint no-constant-binary-expression: "error"*/

const foo = a ?? (doSomething(), undefined) ?? b;
//          ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

const bar = a ?? (something = null) ?? b;
//          ^^^^^^^^^^^^^^^^^^^^^^^

[nissy-dev]

@mdjermanovic Thank you for your review!
I update my codes based on your comments. I would appreciate if you could review again.

[mdjermanovic]

Just one small suggestion, then LGTM.

[nzakas]

LGTM pending @mdjermanovic's review.

[mdjermanovic]

LGTM, thanks!