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fix(minifier): inline multiple variable declarations at once #13477

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Merged
graphite-app merged 1 commit into from
Aug 31, 2025
Merged

fix(minifier): inline multiple variable declarations at once #13477

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115 changes: 60 additions & 55 deletions crates/oxc_minifier/src/peephole/minimize_statements.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -1038,65 +1038,70 @@ impl<'a> PeepholeOptimizations {
if Self::keep_top_level_var_in_script_mode(ctx) {
return false;
}
let Some(Statement::VariableDeclaration(prev_var_decl)) = stmts.last_mut() else {
return false;
};
if prev_var_decl.kind.is_using() {
return false;
}

let last_non_inlined_index = prev_var_decl.declarations.iter_mut().rposition(|prev_decl| {
let Some(prev_decl_init) = &mut prev_decl.init else {
return true;
};
let BindingPatternKind::BindingIdentifier(prev_decl_id) = &prev_decl.id.kind else {
return true;
};
if ctx.is_expression_whose_name_needs_to_be_kept(prev_decl_init) {
return true;
}
let Some(symbol_value) =
ctx.state.symbol_values.get_symbol_value(prev_decl_id.symbol_id())
else {
return true;
};
// we should check whether it's exported by `symbol_value.exported`
// because the variable might be exported with `export { foo }` rather than `export var foo`
if symbol_value.exported
|| symbol_value.read_references_count > 1
|| symbol_value.write_references_count > 0
{
return true;
}
let replaced = Self::substitute_single_use_symbol_in_expression(
expr_in_stmt,
&prev_decl_id.name,
prev_decl_init,
prev_decl_init.may_have_side_effects(ctx),
ctx,
);
if replaced != Some(true) {
return true;
}
false
});
match last_non_inlined_index {
None => {
// all inlined
stmts.pop();
true
}
Some(last_non_inlined_index)
if last_non_inlined_index + 1 == prev_var_decl.declarations.len() =>
{
// no change
false
let mut inlined = false;
while let Some(Statement::VariableDeclaration(prev_var_decl)) = stmts.last_mut() {
if prev_var_decl.kind.is_using() {
break;
}
Some(last_non_inlined_index) => {
prev_var_decl.declarations.truncate(last_non_inlined_index + 1);
true

let last_non_inlined_index =
prev_var_decl.declarations.iter_mut().rposition(|prev_decl| {
let Some(prev_decl_init) = &mut prev_decl.init else {
return true;
};
let BindingPatternKind::BindingIdentifier(prev_decl_id) = &prev_decl.id.kind
else {
return true;
};
if ctx.is_expression_whose_name_needs_to_be_kept(prev_decl_init) {
return true;
}
let Some(symbol_value) =
ctx.state.symbol_values.get_symbol_value(prev_decl_id.symbol_id())
else {
return true;
};
// we should check whether it's exported by `symbol_value.exported`
// because the variable might be exported with `export { foo }` rather than `export var foo`
if symbol_value.exported
|| symbol_value.read_references_count > 1
|| symbol_value.write_references_count > 0
{
return true;
}
let replaced = Self::substitute_single_use_symbol_in_expression(
expr_in_stmt,
&prev_decl_id.name,
prev_decl_init,
prev_decl_init.may_have_side_effects(ctx),
ctx,
);
if replaced != Some(true) {
return true;
}
false
});
match last_non_inlined_index {
None => {
// all inlined
stmts.pop();
inlined = true;
}
Some(last_non_inlined_index)
if last_non_inlined_index + 1 == prev_var_decl.declarations.len() =>
{
// no change
break;
}
Some(last_non_inlined_index) => {
prev_var_decl.declarations.truncate(last_non_inlined_index + 1);
inlined = true;
break;
}
}
}
inlined
}

/// Returns Some(true) when the expression is successfully replaced.
Expand Down
75 changes: 75 additions & 0 deletions crates/oxc_minifier/tests/peephole/dead_code_elimination.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -271,3 +271,78 @@ fn dce_from_terser() {
"console.log(foo, bar, Baz);",
);
}

#[test]
fn dce_iterations() {
test(
"
var a1 = 'a1'
var a2 = 'a2'
var a3 = 'a3'
var a4 = 'a4'
var a5 = 'a5'
var a6 = 'a6'
var a7 = 'a7'
var a8 = 'a8'
var a9 = 'a9'
var a10 = 'a10'
var a11 = 'a11'
var a12 = 'a12'
var a13 = 'a13'
var a14 = 'a14'
var a15 = 'a15'
var a16 = 'a16'
var a17 = 'a17'
var a18 = 'a18'
var a19 = 'a19'
var a20 = 'a20'
var arr = [
a1,
a2,
a3,
a4,
a5,
a6,
a7,
a8,
a9,
a10,
a11,
a12,
a13,
a14,
a15,
a16,
a17,
a18,
a19,
a20
]
console.log(arr)
",
"
console.log([
'a1',
'a2',
'a3',
'a4',
'a5',
'a6',
'a7',
'a8',
'a9',
'a10',
'a11',
'a12',
'a13',
'a14',
'a15',
'a16',
'a17',
'a18',
'a19',
'a20'
])
",
);
}
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