What version of Oxlint are you using?

1.62.0

What command did you run?

oxlint --fix test.ts

What does your .oxlintrc.json (or oxlint.config.ts) config file look like?

{
  "categories": {
    "correctness": "off"
  },
  "plugins": ["unicorn"],
  "rules": {
    "unicorn/prefer-array-some": "error"
  }
}

What happened?

Disclosure: this issue was drafted with AI assistance and reviewed by me before submission, per the AI Usage Policy

What happened?

The auto-fix performs a literal find/findLast → some token swap and leaves the surrounding === undefined/!== undefined/== null/!= null comparison untouched. Since Array#some() always returns a boolean, the comparison becomes a constant — silently inverting (or trivializing) the branch logic.

Minimal reproduction

// test.ts
const arr = [1, 2, 3];
if (arr.find((x) => x === 2) === undefined) {
  console.log('not found');
} else {
  console.log('found');
}

After oxlint --fix

const arr = [1, 2, 3];
if (arr.some((x) => x === 2) === undefined) {  // ← always false
  console.log('not found');                    // ← unreachable
} else {
  console.log('found');                        // ← always taken
}

All affected variants

All five comparison variants exhibit the same naive token-swap behavior:

Runtime verification

const empty = [];
const has2 = [1, 2, 3];
// Original — correct
empty.find(x => x === 2) === undefined  // true  (no match)
has2.find(x => x === 2) === undefined   // false (match)
// After autofix — broken
empty.some(x => x === 2) === undefined  // false (always)
has2.some(x => x === 2) === undefined   // false (always)

This caused a real production bug in our codebase where a deduplication check became inverted, causing every value to be flagged as a duplicate.

Comparison with upstream eslint-plugin-unicorn

Per the upstream rule docs:

This rule is fixable for .filter(…).length checks and .{findIndex,findLastIndex}(…)
This rule provides a suggestion for .{find,findLast}(…)

The upstream plugin deliberately classifies .find()/.findLast() rewrites as suggestions only (require human review) — quoting the original PR:

"because autofixing isn't safe in all cases." It seems Oxlint's port treats this as an autofix instead.

Expected behavior

Either:

1. Produce a semantically correct fix that handles the surrounding comparison:
   • arr.find(p) === undefined/== null → !arr.some(p)
   • arr.find(p) !== undefined/!= null → arr.some(p)
2. Mark the rewrite as a suggestion (not autofix) for .find()/.findLast() patterns, matching upstream behavior.