fix(minifier): keep variables that are modified by combined assignments made by minification

[sapphi-red]

(function() {
  let v;
  window.foo = function() {
    return v ?? (v = bar());
  }
})()

was compressed to

(function() {
  window.foo = function() {
    return bar();
  }
})()

. But this changes the semantics because bar() will be executed every time window.foo() is called after the minification.

This was caused by not updating the semantics information when compressing v ?? (v = bar()) into v ??= bar() (and other similar ones).

This PR fixes that by updating the semantics information when those compressions are applied.

[sapphi-red]

• feat(minifier): support remaining expressions for single use variable inlining #13280
• feat(ecmascript): implement MayHaveSideEffects for AssignmentTarget #13279
• feat(minifier): support more statements for single use variable inlining #13277
• feat(minifier): support more expressions for single use variable inlining #13276
• feat(minifier): implement basic single use variable inlining #13275
• feat(minifier): remove unnecessary parenthesis from nested optional chaining #13268
• feat(minifier): remove unused assignments for vars #13231
• fix(minifier): keep variables that are modified by combined assignments made by minification #13267 👈 (View in Graphite)
• fix(minifier): keep property access before call expressions as-is to preserve this value #13278
• main

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[codspeed-hq]

CodSpeed Instrumentation Performance Report

Merging #13267 will not alter performance

_{Comparing 08-23-fix_minifier_keep_variables_that_are_modified_by_combined_assignments_made_by_minification (0e804aa) with main (e7a49ed)¹}

Summary

✅ 34 untouched benchmarks

Footnotes

1. No successful run was found on main (0e804aa) during the generation of this report, so e7a49ed was used instead as the comparison base. There might be some changes unrelated to this pull request in this report. ↩

[Copilot]

Pull Request Overview

This PR fixes a minification bug where variables modified by combined assignments were incorrectly removed during dead code elimination. The issue occurred when expressions like v ?? (v = bar()) were compressed to v ??= bar() without updating the semantic information to mark the variable as being read.

• Updated peephole optimizations to mark variables as read when creating combined assignment operators
• Added comprehensive test coverage for various assignment operator transformations
• Fixed semantic analysis to prevent incorrect variable elimination

Reviewed Changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 2 comments.

File	Description
crates/oxc_minifier/tests/peephole/oxc.rs	Added test cases covering the variable elimination bug for different assignment operators
crates/oxc_minifier/src/peephole/minimize_logical_expression.rs	Updated to mark variables as read when transforming to combined assignments
crates/oxc_minifier/src/peephole/minimize_conditions.rs	Updated to mark variables as read when creating assignment operators from binary expressions

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[graphite-app]

Merge activity

• Aug 24, 8:30 AM UTC: Boshen added this pull request to the Graphite merge queue.
• Aug 24, 8:49 AM UTC: Merged by the Graphite merge queue.