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Merged
merged 1 commit into from
Jul 17, 2025
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refactor(minifier): do not remove unused assignment expression yet #12367

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66 changes: 34 additions & 32 deletions crates/oxc_minifier/src/peephole/remove_unused_variable_declaration.rs
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Original file line number Diff line number Diff line change
@@ -1,4 +1,3 @@
use oxc_allocator::TakeIn;
use oxc_ast::ast::*;

use crate::{CompressOptionsUnused, ctx::Ctx};
Expand Down Expand Up @@ -48,38 +47,38 @@ impl<'a> PeepholeOptimizations {

pub fn remove_unused_assignment_expression(
&self,
e: &mut Expression<'a>,
state: &mut State,
ctx: &mut Ctx<'a, '_>,
_e: &mut Expression<'a>,
_state: &mut State,
_ctx: &mut Ctx<'a, '_>,
) -> bool {
let Expression::AssignmentExpression(assign_expr) = e else { return false };
if matches!(
ctx.state.options.unused,
CompressOptionsUnused::Keep | CompressOptionsUnused::KeepAssign
) {
return false;
}
let Some(SimpleAssignmentTarget::AssignmentTargetIdentifier(ident)) =
assign_expr.left.as_simple_assignment_target()
else {
return false;
};
if Self::keep_top_level_var_in_script_mode(ctx) {
return false;
}
let Some(reference_id) = ident.reference_id.get() else { return false };
let Some(symbol_id) = ctx.scoping().get_reference(reference_id).symbol_id() else {
return false;
};
// Keep error for assigning to `const foo = 1; foo = 2`.
if ctx.scoping().symbol_flags(symbol_id).is_const_variable() {
return false;
}
if !ctx.scoping().get_resolved_references(symbol_id).all(|r| !r.flags().is_read()) {
return false;
}
*e = assign_expr.right.take_in(ctx.ast);
state.changed = true;
// let Expression::AssignmentExpression(assign_expr) = e else { return false };
// if matches!(
// ctx.state.options.unused,
// CompressOptionsUnused::Keep | CompressOptionsUnused::KeepAssign
// ) {
// return false;
// }
// let Some(SimpleAssignmentTarget::AssignmentTargetIdentifier(ident)) =
// assign_expr.left.as_simple_assignment_target()
// else {
// return false;
// };
// if Self::keep_top_level_var_in_script_mode(ctx) {
// return false;
// }
// let Some(reference_id) = ident.reference_id.get() else { return false };
// let Some(symbol_id) = ctx.scoping().get_reference(reference_id).symbol_id() else {
// return false;
// };
// // Keep error for assigning to `const foo = 1; foo = 2`.
// if ctx.scoping().symbol_flags(symbol_id).is_const_variable() {
// return false;
// }
// if !ctx.scoping().get_resolved_references(symbol_id).all(|r| !r.flags().is_read()) {
// return false;
// }
// *e = assign_expr.right.take_in(ctx.ast);
// state.changed = true;
false
}

Expand Down Expand Up @@ -121,11 +120,13 @@ mod test {
}

#[test]
#[ignore]
fn remove_unused_assignment_expression() {
let options = CompressOptions::smallest();
test_options("var x = 1; x = 2;", "", &options);
test_options("var x = 1; x = 2;", "", &options);
test_options("var x = 1; x = foo();", "foo()", &options);
test_same_options("export let foo; foo = 0;", &options);
test_same_options("var x = 1; x = 2, foo(x)", &options);
test_same_options("function foo() { return t = x(); } foo();", &options);
test_options(
Expand All @@ -141,6 +142,7 @@ mod test {
}

#[test]
#[ignore]
fn keep_in_script_mode() {
let options = CompressOptions::smallest();
let source_type = SourceType::cjs();
Expand Down
10 changes: 5 additions & 5 deletions tasks/minsize/minsize.snap
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Original file line number Diff line number Diff line change
@@ -1,7 +1,7 @@
| Oxc | ESBuild | Oxc | ESBuild |
Original | minified | minified | gzip | gzip | Fixture
-------------------------------------------------------------------------------------
72.14 kB | 23.45 kB | 23.70 kB | 8.46 kB | 8.54 kB | react.development.js
72.14 kB | 23.49 kB | 23.70 kB | 8.47 kB | 8.54 kB | react.development.js

173.90 kB | 59.51 kB | 59.82 kB | 19.18 kB | 19.33 kB | moment.js

Expand All @@ -11,17 +11,17 @@ Original | minified | minified | gzip | gzip | Fixture

544.10 kB | 71.38 kB | 72.48 kB | 25.85 kB | 26.20 kB | lodash.js

555.77 kB | 270.80 kB | 270.13 kB | 88.24 kB | 90.80 kB | d3.js
555.77 kB | 270.83 kB | 270.13 kB | 88.25 kB | 90.80 kB | d3.js

1.01 MB | 440.17 kB | 458.89 kB | 122.37 kB | 126.71 kB | bundle.min.js

1.25 MB | 647 kB | 646.76 kB | 160.28 kB | 163.73 kB | three.js

2.14 MB | 716.10 kB | 724.14 kB | 161.76 kB | 181.07 kB | victory.js
2.14 MB | 716.12 kB | 724.14 kB | 161.80 kB | 181.07 kB | victory.js

3.20 MB | 1.01 MB | 1.01 MB | 324.08 kB | 331.56 kB | echarts.js

6.69 MB | 2.24 MB | 2.31 MB | 462.45 kB | 488.28 kB | antd.js
6.69 MB | 2.25 MB | 2.31 MB | 463.06 kB | 488.28 kB | antd.js

10.95 MB | 3.34 MB | 3.49 MB | 856.90 kB | 915.50 kB | typescript.js
10.95 MB | 3.35 MB | 3.49 MB | 860.95 kB | 915.50 kB | typescript.js

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