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feat(minifier): do not flip if/else when it would produce longer result #17556

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Merged
Boshen merged 3 commits into from
Jan 15, 2026
Merged

feat(minifier): do not flip if/else when it would produce longer result #17556

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ad310aa
feat(minifier): do not flip if/else when it would produce longer result
armano2 Jan 1, 2026
b6893ab
Merge branch 'main' into feat/minifier-do-not-flip-if-statements
armano2 Jan 8, 2026
c50251c
Merge remote-tracking branch 'upstream/main' into feat/minifier-do-no…
armano2 Jan 14, 2026
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20 changes: 14 additions & 6 deletions crates/oxc_minifier/src/peephole/minimize_conditions.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -637,13 +637,21 @@ mod test {
if (!x) {
for (;;) foo();
for (;;) bar();
} else if (y) for (;;) f();",
} else for (;;) f();",
"
if (x) {
if (y) for (; ; ) f();
} else {
for (; ; ) foo();
for (; ; ) bar();}",
if (x) for (;;) f();
else {
for (;;) foo();
for (;;) bar();
}
",
);
test_same(
"
if (!x) {
for (;;) foo();
for (;;) bar();
} else if (y) for (;;) f();",
);
test_same("if(!a&&!b) {for(;;)foo(); for(;;)bar()} else if(y) for(;;) f()");
}
Expand Down
26 changes: 19 additions & 7 deletions crates/oxc_minifier/src/peephole/minimize_if_statement.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -89,7 +89,8 @@ impl<'a> PeepholeOptimizations {
// "yes" is not missing (and is not an expression)
if let Some(alternate) = &mut if_stmt.alternate {
// "yes" is not missing (and is not an expression) and "no" is not missing
if let Expression::UnaryExpression(unary_expr) = &mut if_stmt.test
if !matches!(alternate, Statement::IfStatement(_))
&& let Expression::UnaryExpression(unary_expr) = &mut if_stmt.test
&& unary_expr.operator.is_not()
{
// "if (!a) return b; else return c;" => "if (a) return c; else return b;"
Expand All @@ -98,6 +99,7 @@ impl<'a> PeepholeOptimizations {
Self::wrap_to_avoid_ambiguous_else(if_stmt, ctx);
ctx.state.changed = true;
}
// "if (!a) {} else if (b) {}" => "if (!a) {} if (b) {}" is handled by minimize_statements
// "if (a) return b; else {}" => "if (a) return b;" is handled by remove_dead_code
} else {
// "no" is missing
Expand Down Expand Up @@ -169,6 +171,19 @@ mod test {
}",
);

test(
"function bar() {
if (!x) {
return null;
} else {
return foo;
}
}",
"function bar() {
return x ? foo : null;
}",
);

test(
"function bar() {
if (!x) {
Expand All @@ -180,12 +195,9 @@ mod test {
}
}",
"function bar() {
if (x) {
if (y)
return foo;
if (z)
return bar;
} else return null;
if (!x) return null;
if (y) return foo;
if (z) return bar;
}",
);

Expand Down
8 changes: 4 additions & 4 deletions tasks/minsize/minsize.snap
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Original file line number Diff line number Diff line change
Expand Up @@ -13,15 +13,15 @@ Original | minified | minified | gzip | gzip | Iterations | Fi

555.77 kB | 267.39 kB | 270.13 kB | 88.00 kB | 90.80 kB | 2 | d3.js

1.01 MB | 439.38 kB | 458.89 kB | 122.06 kB | 126.71 kB | 2 | bundle.min.js
1.01 MB | 439.37 kB | 458.89 kB | 122.06 kB | 126.71 kB | 2 | bundle.min.js

1.25 MB | 642.66 kB | 646.76 kB | 159.40 kB | 163.73 kB | 2 | three.js

2.14 MB | 711.14 kB | 724.14 kB | 160.43 kB | 181.07 kB | 2 | victory.js
2.14 MB | 711.11 kB | 724.14 kB | 160.43 kB | 181.07 kB | 2 | victory.js

3.20 MB | 1.00 MB | 1.01 MB | 322.59 kB | 331.56 kB | 3 | echarts.js
3.20 MB | 1.00 MB | 1.01 MB | 322.58 kB | 331.56 kB | 3 | echarts.js

6.69 MB | 2.22 MB | 2.31 MB | 458.44 kB | 488.28 kB | 4 | antd.js

10.95 MB | 3.33 MB | 3.49 MB | 853.35 kB | 915.50 kB | 4 | typescript.js
10.95 MB | 3.33 MB | 3.49 MB | 853.30 kB | 915.50 kB | 4 | typescript.js

6 changes: 3 additions & 3 deletions tasks/track_memory_allocations/allocs_minifier.snap
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Original file line number Diff line number Diff line change
@@ -1,14 +1,14 @@
File | File size || Sys allocs | Sys reallocs || Arena allocs | Arena reallocs | Arena bytes
-------------------------------------------------------------------------------------------------------------------------------------------
checker.ts | 2.92 MB || 4128 | 1669 || 152592 | 28237
checker.ts | 2.92 MB || 4128 | 1669 || 152600 | 28244

cal.com.tsx | 1.06 MB || 21098 | 474 || 37138 | 4586

RadixUIAdoptionSection.jsx | 2.52 kB || 65 | 3 || 30 | 6

pdf.mjs | 567.30 kB || 4691 | 569 || 47453 | 7730
pdf.mjs | 567.30 kB || 4691 | 569 || 47464 | 7730

antd.js | 6.69 MB || 10723 | 2505 || 331649 | 69358
antd.js | 6.69 MB || 10723 | 2505 || 331648 | 69358

binder.ts | 193.08 kB || 431 | 119 || 7075 | 824

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