fix(linter/unicorn/prefer-math-trunc): don't suggest a fix for a side-effecting assignment LHS#23531
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hyf0 wants to merge 1 commit into
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fix(linter/unicorn/prefer-math-trunc): don't suggest a fix for a side-effecting assignment LHS#23531hyf0 wants to merge 1 commit into
hyf0 wants to merge 1 commit into
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…-effecting assignment LHS The `x |= 0` → `x = Math.trunc(x)` suggestion duplicates the assignment LHS source text. For a side-effecting LHS this re-runs the side effect: e.g. `foo[i++] |= 0` was suggested as `foo[i++] = Math.trunc(foo[i++])`, evaluating `i++` twice; likewise `obj[bar()] ^= 0`, `getFoo().baz >>= 0`, etc. Detect a side effect in the LHS (Call / New / Update / Await / Yield / Assignment / dynamic `import` / `delete`, matching eslint-plugin-unicorn's `hasSideEffect`) and report without a suggestion in that case. Side-effect-free targets (`x`, `foo.bar`, `[foo][0]`) still get the fix.
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camc314
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Jun 17, 2026
camc314
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Thanks for working on this.
The approach you've taken doesn't work correctly in certain scenarios.
For example, given the following:
obj.foo.bar |= 0;The current suggestion would become:
obj.foo.bar = Math.trunc(obj.foo.bar);which evaluates obj.foo twice.
If that property read is a getter/proxy, this suggestion can change behaviour.
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Bug
The
x |= 0→x = Math.trunc(x)suggestion is built by duplicating the assignment LHS source text. For a side-effecting LHS this re-runs the side effect:Expected
Side-effecting LHS should still be reported but offered NO fix/suggestion — eslint-plugin-unicorn guards exactly this (
if (!isAssignment || !hasSideEffect(left, sourceCode))).Fix
Detect a side effect in the assignment LHS (Call / New / Update / Await / Yield / Assignment / dynamic
import/delete— matching eslint-utilshasSideEffect) via a smallVisitwalker, and report without a suggestion in that case. Side-effect-free targets (x,foo.bar,[foo][0]) still get the fix. Regression tests added for the side-effecting cases.Prepared with AI assistance.