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fix(minifier): always keep the last value of sequence expression (#8490)

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Caught in react app:

```
React.useEffect(() => {
  isMountRef.current = false;
  return () => {
    isMountRef.current = true;
  };
}, []);
```

->

```
React.useEffect(() => isMountRef.current = !1, []);
```

Two problems: there were no unit tests guarding this, no good way of knowing when code gets deleted.
This commit is contained in:
Boshen 2025-01-14 15:35:00 +00:00
parent 31746754a8
commit 65854630be
1 changed files with 3 additions and 6 deletions
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9
crates/oxc_minifier/src/ast_passes/peephole_remove_dead_code.rs
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@ -496,8 +496,6 @@ impl<'a, 'b> PeepholeRemoveDeadCode {
sequence_expr: &mut SequenceExpression<'a>,
ctx: Ctx<'a, 'b>,
) -> Option<Expression<'a>> {
let should_include_ret_val =
!matches!(ctx.parent(), Ancestor::ExpressionStatementExpression(_));
let should_keep_as_sequence_expr = matches!(
ctx.parent(),
Ancestor::CallExpressionCallee(_) | Ancestor::TaggedTemplateExpressionTag(_)
@ -510,9 +508,7 @@ impl<'a, 'b> PeepholeRemoveDeadCode {
let (should_fold, new_len) = sequence_expr.expressions.iter().enumerate().fold(
(false, 0),
|(mut should_fold, mut new_len), (i, expr)| {
if expr.may_have_side_effects()
|| (should_include_ret_val && i == sequence_expr.expressions.len() - 1)
{
if i == sequence_expr.expressions.len() - 1 || expr.may_have_side_effects() {
new_len += 1;
} else {
should_fold = true;
@ -529,7 +525,7 @@ impl<'a, 'b> PeepholeRemoveDeadCode {
let mut new_exprs = ctx.ast.vec_with_capacity(new_len);
let len = sequence_expr.expressions.len();
for (i, expr) in sequence_expr.expressions.iter_mut().enumerate() {
if expr.may_have_side_effects() || (should_include_ret_val && i == len - 1) {
if i == len - 1 || expr.may_have_side_effects() {
new_exprs.push(ctx.ast.move_expression(expr));
}
}
@ -744,6 +740,7 @@ mod test {
fold("var obj = Object((null, 2, 3), 1, 2);", "var obj = Object(3, 1, 2);");
fold_same("(0 instanceof 0, foo)");
fold_same("(0 in 0, foo)");
fold_same("React.useEffect(() => (isMountRef.current = false, () => { isMountRef.current = true; }), [])");
}
#[test]