fix(eslint-plugin): [prefer-optional-chain] use suggestion instead of autofix for trailing binary operator by mdm317 · Pull Request #12328 · typescript-eslint/typescript-eslint

mdm317 · 2026-05-12T10:29:09Z

PR Checklist

Addresses an existing open issue: fixes Bug: [prefer-optional-chain] invalid fix with array access by index #11917
That issue was marked as accepting prs
Steps in Contributing were taken

Overview

Downgrades the trailing-chain autofix added in pr-11533 to a suggestion.
Pre-existing trailing nullish-equality chains before [pr-11533] (e.g. foo == null || foo.bar == undefined) are still autofixed.
- Should we also change the above case in this PR?
  - If the last chain uses any binary operator, should we also switch it to a suggestion?

Additional Notes

It seems the unsafe rewrites only occur when the compared value is non-primitive.
When the compared value is primitive, the rewrite appears to be safe.

Possible options:

keep it as an autofix, or
gate it behind an opt-in option

typescript-eslint · 2026-05-12T10:29:13Z

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kirkwaiblinger · 2026-05-18T17:12:01Z

Pre-existing trailing nullish-equality chains before [pr-11533] (e.g. foo == null || foo.bar == undefined) are still autofixed.

Should we also change the above case in this PR?

It would help to have a complete example, but the following is sound and doesn't need to be changed:

Playground

declare const foo: { bar: string | undefined } | null
foo == null || foo.bar == undefined

* If the last chain uses any binary operator, should we also switch it to a suggestion?

Can you provide an example of what you mean?

Additional Notes

It seems the unsafe rewrites only occur when the compared value is non-primitive. When the compared value is primitive, the rewrite appears to be safe.

Possible options:

keep it as an autofix, or

gate it behind an opt-in option

Can you provide an example of what you mean?

kirkwaiblinger

The actual code changes here look good to me! And all the test cases I looked at looked like the correct change. Didn't check closely yet whether there any missed cases...

Would like some clarity on the questions in the PR description, though, before doing a thorough pass for any missed cases.

Thanks!

mdm317 · 2026-05-28T18:32:16Z

Sorry — my previous reply had mistakes in both the explanation and the examples.
Here's a corrected version.

Re: Q1 & Q2

My original example was wrong.

There are still a few cases where the last operand is neither a nullish check nor a truthy/falsy check.
Should we keep those as autofixes?

declare const foo: { bar: number };
!foo || foo.bar === null;

Personally, I'd recommend downgrading this not reporting it at all.
The code above can still cause issues such as #11700
See also @kirkwaiblinger's comment in #11700.

Re: Q3

The RHS constraint is literal, not primitive — I misspoke earlier.
Please disregard my comments about the opt-in option.

I'd suggest restricting the autofix to cases where all three conditions below hold.

The chain should be used in a boolean context.

if (foo && foo.bar === 5) { /* safe */ }
const x = foo && foo.bar === 5; // type of x changes

The RHS should be a literal.

A non-literal RHS breaks the algorithm implemented in #11533.
Two such cases are currently open:
- May be undefined at runtime but not in the type (e.g. array / Record)
  (#11917):
  foo && foo.bar === arr[4]
- RHS references the chain itself
  (#12204, #12200):
  a && a.b === a

No prior operand should be a truthy/falsy check

declare const s: string;

// before — when s is ""
!s || s.lastIndexOf('.') !== -1; // → true
// after autofix — when s is ""
s?.lastIndexOf('.') !== -1;      // → false

If anything is unclear or seems off, I'd appreciate a follow-up — happy to clarify.

JoshuaKGoldberg · 2026-06-15T16:29:35Z

@mdm317 can you confirm you stand behind through your response? The one you most recently posted looks to be pretty directly AI copy & paste. https://typescript-eslint.io/contributing/ai-policy

mdm317 · 2026-06-20T17:46:59Z

@JoshuaKGoldberg
Yes, I stand behind my response.

I used AI to help translate my thoughts into English, not to generate the response itself, which may have made the wording sound AI-generated.

I've updated the comment to better explain my reasoning.
If anything seems unclear, please let me know.

kirkwaiblinger

Sorry — my previous reply had mistakes in both the explanation and the examples. Here's a corrected version.

Re: Q1 & Q2

My original example was wrong.

There are still a few cases where the last operand is neither a nullish check nor a truthy/falsy check. Should we keep those as autofixes?
declare const foo: { bar: number };
!foo || foo.bar === null;
Personally, I'd recommend downgrading this not reporting it at all. The code above can still cause issues such as #11700 See also @kirkwaiblinger's comment in #11700.

As far as this PR, I don't think we change anything here. Note that it's already a suggestion currently, not an autofix.

Re: Q3

The RHS constraint is literal, not primitive — I misspoke earlier. Please disregard my comments about the opt-in option.

I'd suggest restricting the autofix to cases where all three conditions below hold.
The chain should be used in a boolean context.
if (foo && foo.bar === 5) { /* safe */ }
const x = foo && foo.bar === 5; // type of x changes
The RHS should be a literal.
A non-literal RHS breaks the algorithm implemented in #11533.
Two such cases are currently open:

May be undefined at runtime but not in the type (e.g. array / Record)
(#11917):
foo && foo.bar === arr[4]

RHS references the chain itself
(#12204, #12200):
a && a.b === a
No prior operand should be a truthy/falsy check
declare const s: string;

// before — when s is ""
!s || s.lastIndexOf('.') !== -1; // → true
// after autofix — when s is ""
s?.lastIndexOf('.') !== -1;      // → false
If anything is unclear or seems off, I'd appreciate a follow-up — happy to clarify.

This PR currently downgrades these cases, which were previously auto-fixed, to a suggestion, which is the expected resolution based on #11917 (comment).

If I understand correctly, the question is whether the autofix should be preserved in special cases that actually can be proven to be safe (satisfying the three conditions above), rather than downgraded to suggestions along with the rest of the cases? I'd say, no, let's not bother, because a) it's of marginal value b) it adds complexity, and c) it will delay merging this PR, which I'm anxious to merge 😄.

Regarding #12328 (comment), translating is a completely valid and understandable use of AI, thank you for letting us know 👍 For whatever reason, the wording in this PR turned out to be rather difficult to understand... You've submitted quite a few high quality PRs previously (which we really appreciate! ❤️) and I think we've always had an easy time understanding the conversations in them, so it was just a bit surprising to see a difference here (and we're bit apprehensive in general these days due to the increasing volume of bad, AI-authored PRs).

In any case, this looks good to me. Thanks for sending! 🙏

mdm317 · 2026-06-21T16:04:42Z

Thanks for the detailed explanation and review!

And thanks for the kind words as well 😊
I'll try to make future PR descriptions a bit clearer.

@kirkwaiblinger

| datasource | package | from | to | | ---------- | -------------------------------- | ------ | ------ | | npm | @typescript-eslint/eslint-plugin | 8.61.0 | 8.62.1 | | npm | @typescript-eslint/parser | 8.61.0 | 8.62.1 | ## [v8.62.1](https://github.com/typescript-eslint/typescript-eslint/blob/HEAD/packages/eslint-plugin/CHANGELOG.md#8621-2026-06-29) ##### 🩹 Fixes - **eslint-plugin:** \[no-unnecessary-type-assertion] parenthesize object literal at left edge of expression statement ([#12443](typescript-eslint/typescript-eslint#12443), [#12418](typescript-eslint/typescript-eslint#12418)) - **eslint-plugin:** \[no-unnecessary-boolean-literal-compare] preserve boolean result in fixer for nullable true comparisons ([#12365](typescript-eslint/typescript-eslint#12365)) - **eslint-plugin:** \[prefer-optional-chain] use suggestion instead of autofix for trailing binary operator ([#12328](typescript-eslint/typescript-eslint#12328)) ##### ❤️ Thank You - Kirk Waiblinger [@kirkwaiblinger](https://github.com/kirkwaiblinger) - mdm317 - Patrick Aleite - 송재욱 See [GitHub Releases](https://github.com/typescript-eslint/typescript-eslint/releases/tag/v8.62.1) for more information. You can read about our [versioning strategy](https://typescript-eslint.io/users/versioning) and [releases](https://typescript-eslint.io/users/releases) on our website. ## [v8.62.0](https://github.com/typescript-eslint/typescript-eslint/blob/HEAD/packages/eslint-plugin/CHANGELOG.md#8620-2026-06-22) ##### 🚀 Features - remove redundant package.json "files" ([#12444](typescript-eslint/typescript-eslint#12444)) ##### ❤️ Thank You - Kirk Waiblinger [@kirkwaiblinger](https://github.com/kirkwaiblinger) See [GitHub Releases](https://github.com/typescript-eslint/typescript-eslint/releases/tag/v8.62.0) for more information. You can read about our [versioning strategy](https://typescript-eslint.io/users/versioning) and [releases](https://typescript-eslint.io/users/releases) on our website. ## [v8.61.1](https://github.com/typescript-eslint/typescript-eslint/blob/HEAD/packages/eslint-plugin/CHANGELOG.md#8611-2026-06-15) ##### 🩹 Fixes - **eslint-plugin:** \[no-unnecessary-template-expression] respect ECMAScript line terminators ([#12388](typescript-eslint/typescript-eslint#12388)) - **eslint-plugin:** \[no-unnecessary-boolean-literal-compare] fix precedence bug in autofix ([#12413](typescript-eslint/typescript-eslint#12413)) - **eslint-plugin:** \[no-unnecessary-type-assertion] wrap object literal in parens when removing TSTypeAssertion in arrow body ([#12394](typescript-eslint/typescript-eslint#12394), [#12393](typescript-eslint/typescript-eslint#12393)) - **eslint-plugin:** \[no-unnecessary-type-assertion] avoid false positive for template literal expressions ([#12281](typescript-eslint/typescript-eslint#12281)) - **eslint-plugin:** \[consistent-indexed-object-style] do not remove comments when fixing ([#12396](typescript-eslint/typescript-eslint#12396), [#10577](typescript-eslint/typescript-eslint#10577)) ##### ❤️ Thank You - Anas [@anasm266](https://github.com/anasm266) - Deftera [@Deftera186](https://github.com/Deftera186) - Kirk Waiblinger [@kirkwaiblinger](https://github.com/kirkwaiblinger) - lumir - Sarath Francis [@sarathfrancis90](https://github.com/sarathfrancis90) See [GitHub Releases](https://github.com/typescript-eslint/typescript-eslint/releases/tag/v8.61.1) for more information. You can read about our [versioning strategy](https://typescript-eslint.io/users/versioning) and [releases](https://typescript-eslint.io/users/releases) on our website.

@kirkwaiblinger

| datasource | package | from | to | | ---------- | -------------------------------- | ------ | ------ | | npm | @typescript-eslint/eslint-plugin | 8.61.0 | 8.62.1 | | npm | @typescript-eslint/parser | 8.61.0 | 8.62.1 | ## [v8.62.1](https://github.com/typescript-eslint/typescript-eslint/blob/HEAD/packages/eslint-plugin/CHANGELOG.md#8621-2026-06-29) ##### 🩹 Fixes - **eslint-plugin:** \[no-unnecessary-type-assertion] parenthesize object literal at left edge of expression statement ([#12443](typescript-eslint/typescript-eslint#12443), [#12418](typescript-eslint/typescript-eslint#12418)) - **eslint-plugin:** \[no-unnecessary-boolean-literal-compare] preserve boolean result in fixer for nullable true comparisons ([#12365](typescript-eslint/typescript-eslint#12365)) - **eslint-plugin:** \[prefer-optional-chain] use suggestion instead of autofix for trailing binary operator ([#12328](typescript-eslint/typescript-eslint#12328)) ##### ❤️ Thank You - Kirk Waiblinger [@kirkwaiblinger](https://github.com/kirkwaiblinger) - mdm317 - Patrick Aleite - 송재욱 See [GitHub Releases](https://github.com/typescript-eslint/typescript-eslint/releases/tag/v8.62.1) for more information. You can read about our [versioning strategy](https://typescript-eslint.io/users/versioning) and [releases](https://typescript-eslint.io/users/releases) on our website. ## [v8.62.0](https://github.com/typescript-eslint/typescript-eslint/blob/HEAD/packages/eslint-plugin/CHANGELOG.md#8620-2026-06-22) ##### 🚀 Features - remove redundant package.json "files" ([#12444](typescript-eslint/typescript-eslint#12444)) ##### ❤️ Thank You - Kirk Waiblinger [@kirkwaiblinger](https://github.com/kirkwaiblinger) See [GitHub Releases](https://github.com/typescript-eslint/typescript-eslint/releases/tag/v8.62.0) for more information. You can read about our [versioning strategy](https://typescript-eslint.io/users/versioning) and [releases](https://typescript-eslint.io/users/releases) on our website. ## [v8.61.1](https://github.com/typescript-eslint/typescript-eslint/blob/HEAD/packages/eslint-plugin/CHANGELOG.md#8611-2026-06-15) ##### 🩹 Fixes - **eslint-plugin:** \[no-unnecessary-template-expression] respect ECMAScript line terminators ([#12388](typescript-eslint/typescript-eslint#12388)) - **eslint-plugin:** \[no-unnecessary-boolean-literal-compare] fix precedence bug in autofix ([#12413](typescript-eslint/typescript-eslint#12413)) - **eslint-plugin:** \[no-unnecessary-type-assertion] wrap object literal in parens when removing TSTypeAssertion in arrow body ([#12394](typescript-eslint/typescript-eslint#12394), [#12393](typescript-eslint/typescript-eslint#12393)) - **eslint-plugin:** \[no-unnecessary-type-assertion] avoid false positive for template literal expressions ([#12281](typescript-eslint/typescript-eslint#12281)) - **eslint-plugin:** \[consistent-indexed-object-style] do not remove comments when fixing ([#12396](typescript-eslint/typescript-eslint#12396), [#10577](typescript-eslint/typescript-eslint#10577)) ##### ❤️ Thank You - Anas [@anasm266](https://github.com/anasm266) - Deftera [@Deftera186](https://github.com/Deftera186) - Kirk Waiblinger [@kirkwaiblinger](https://github.com/kirkwaiblinger) - lumir - Sarath Francis [@sarathfrancis90](https://github.com/sarathfrancis90) See [GitHub Releases](https://github.com/typescript-eslint/typescript-eslint/releases/tag/v8.61.1) for more information. You can read about our [versioning strategy](https://typescript-eslint.io/users/versioning) and [releases](https://typescript-eslint.io/users/releases) on our website.

fix: use suggest for trailing binary operator

34b96b4

mdm317 marked this pull request as ready for review May 12, 2026 10:41

kirkwaiblinger reviewed May 18, 2026

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kirkwaiblinger added 1 approval >=1 team member has approved this PR; we're now leaving it open for more reviews before we merge and removed awaiting response Issues waiting for a reply from the OP or another party labels Jun 21, 2026

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Apply strict code-quality lint rules to scripts tree (Fixes #2282) vybestack/llxprt-code#2284

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fix(eslint-plugin): [prefer-optional-chain] use suggestion instead of autofix for trailing binary operator#12328

fix(eslint-plugin): [prefer-optional-chain] use suggestion instead of autofix for trailing binary operator#12328
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