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Keep __proto__ object keys as written when printing and synthesizing object literals #40812

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Keep __proto__ object keys as written when printing and synthesizing object literals #40812

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a41b7db
Keep __proto__ object keys as written when printing and synthesizing …
robobun Aug 28, 2026
453edad
Set the export alias flags after building the property
robobun Aug 28, 2026
f41ff0f
Shorten the comments on the __proto__ key helpers
robobun Aug 28, 2026
86989c6
Mark a __proto__ export name computed in the server components client…
robobun Aug 28, 2026
59abc70
Test the dev server class export, the JSON namespace import and destr…
robobun Aug 28, 2026
6339501
Test the server component proxy module with a __proto__ export in the…
robobun Aug 29, 2026
974ca35
Use describe.each for the minify variants of the __proto__ tests
robobun Aug 29, 2026
2f92d86
Merge branch 'main' into farm/946e2745/fix-proto-property-keys
robobun Sep 6, 2026
cf4db6c
Test several data files with a top-level __proto__ key, and keep the …
robobun Sep 6, 2026
9a2c5f7
Merge remote-tracking branch 'origin/main' into farm/946e2745/fix-pro…
robobun Sep 9, 2026
d351933
Add the default/ExportSpecialName esbuild case and a JSON named-impor…
robobun Sep 9, 2026
33131a1
Set the export getter flags after building the property
robobun Sep 9, 2026
5454ebf
ci: retrigger
robobun Sep 10, 2026
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4 changes: 1 addition & 3 deletions src/ast/e.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -1481,9 +1481,7 @@ impl Object {
}
}

/// Data-file parsers (JSON/JSON5/TOML/YAML) define every key as an own
/// property, so an own `"__proto__"` string key must be marked computed:
/// a plain `"__proto__":` key in a printed object literal sets the prototype.
/// A synthesized `"__proto__"` key is computed: a plain `__proto__:` would set the prototype.
pub fn own_key_property_flags(key: &Expr) -> crate::flags::PropertySet {
match &key.data {
crate::expr::Data::EString(key_str) if key_str.eql_comptime(b"__proto__") => {
Expand Down
8 changes: 4 additions & 4 deletions src/bundler/AstBuilder.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -369,11 +369,11 @@ impl<'a, 'bump> AstBuilder<'a, 'bump> {
self.symbols[ref_.inner_index() as usize].original_name;
// ImportScanner.recordExportedBinding → recordExport
self.record_export(binding.loc, original_name.slice(), ref_)?;
let key =
Expr::init(E::String::init(original_name.slice()), binding.loc);
export_props.push(G::Property {
key: Some(Expr::init(
E::String::init(original_name.slice()),
binding.loc,
)),
flags: E::own_key_property_flags(&key),
key: Some(key),
value: Some(Expr::init_identifier(ref_, binding.loc)),
..Default::default()
});
Expand Down
1 change: 1 addition & 0 deletions src/bundler/bundle_v2.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -3638,6 +3638,7 @@ pub mod bv2_impl {
..Default::default()
});
*client_item = G::Property {
flags: E::own_key_property_flags(&export_name),
key: Some(export_name),
value: Some(server.new_expr(E::Object {
properties: bun_ast::g::PropertyList::from_owned_slice(Box::new([
Expand Down
9 changes: 7 additions & 2 deletions src/bundler/linker_context/doStep5.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -557,7 +557,7 @@ impl LinkerContext<'_> {
stmts: stmts_eat1!(Stmt::allocate(arena, S::Return { value: Some(value) }, loc,)),
loc,
};
properties.push(G::Property {
let mut property = G::Property {
key: Some(Expr::allocate(
arena,
// TODO: test emoji work as expected (relevant for WASM exports)
Expand All @@ -577,7 +577,11 @@ impl LinkerContext<'_> {
loc,
)),
..Default::default()
});
};
let key_flags =
E::own_key_property_flags(property.key.as_ref().expect("infallible: prop has key"));
property.flags = key_flags;
properties.push(property);
if lifted_setter_param.is_valid()
&& exp_data.source_index.get() == id
&& self
Expand Down Expand Up @@ -609,6 +613,7 @@ impl LinkerContext<'_> {
..Default::default()
});
setter_properties.push(G::Property {
flags: key_flags,
key: Some(Expr::allocate(
arena,
// SAFETY: as for the getter key above.
Expand Down
3 changes: 3 additions & 0 deletions src/bundler/linker_context/generateCodeForFileInChunkJS.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -460,6 +460,8 @@ pub fn generate_code_for_file_in_chunk_js<'r, 'src>(
// empty" invariant makes that drop a no-op today, but
// `ptr::write` enforces it structurally.
let key = prop.key;
// keeps a "__proto__" key computed
let flags = prop.flags;
let value_loc =
prop.value.as_ref().expect("infallible: prop has value").loc;
// SAFETY: `prop` is a valid `&mut G::Property` slot;
Expand All @@ -470,6 +472,7 @@ pub fn generate_code_for_file_in_chunk_js<'r, 'src>(
prop,
G::Property {
key,
flags,
value: Some(Expr::init_identifier(export_ref, value_loc)),
..Default::default()
},
Expand Down
54 changes: 31 additions & 23 deletions src/js_parser/lower/lower_esm_exports_hmr.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -77,12 +77,14 @@ impl<'a> ConvertESMExportsForHmr<'a> {
// if the symbol is not used, we don't need to preserve
// a binding in this scope. we can move it to the exports object.
if symbol.use_count_estimate == 0 && value.can_be_moved() {
let key = Expr::init(
// SAFETY: arena-owned name slice valid for the parse.
E::EString::init(symbol.original_name.slice()),
binding.loc,
);
self.export_props.push(G::Property {
key: Some(Expr::init(
// SAFETY: arena-owned name slice valid for the parse.
E::EString::init(symbol.original_name.slice()),
binding.loc,
)),
flags: E::own_key_property_flags(&key),
key: Some(key),
value: Some(value),
..Default::default()
});
Expand Down Expand Up @@ -257,16 +259,18 @@ impl<'a> ConvertESMExportsForHmr<'a> {

let class_name_ref = st.class.class_name.unwrap().ref_;
// Export as CommonJS
let key = Expr::init(
// SAFETY: arena-owned name slice valid for the parse.
E::EString::init(
p.symbols[class_name_ref.inner_index() as usize]
.original_name
.slice(),
),
stmt.loc,
);
self.export_props.push(G::Property {
key: Some(Expr::init(
// SAFETY: arena-owned name slice valid for the parse.
E::EString::init(
p.symbols[class_name_ref.inner_index() as usize]
.original_name
.slice(),
),
stmt.loc,
)),
flags: E::own_key_property_flags(&key),
key: Some(key),
value: Some(Expr::init_identifier(class_name_ref, stmt.loc)),
..Default::default()
});
Expand Down Expand Up @@ -350,12 +354,14 @@ impl<'a> ConvertESMExportsForHmr<'a> {

if let Some(alias) = &st.alias {
// 'export * as ns from' creates one named property.
self.export_props.push(G::Property {
let key = Expr::init(
// SAFETY: arena-owned name slice valid for the parse.
key: Some(Expr::init(
E::EString::init(alias.original_name.slice()),
stmt.loc,
)),
E::EString::init(alias.original_name.slice()),
stmt.loc,
);
self.export_props.push(G::Property {
flags: E::own_key_property_flags(&key),
key: Some(key),
value: Some(Expr::init_identifier(deduped.namespace_ref, stmt.loc)),
..Default::default()
});
Expand Down Expand Up @@ -621,11 +627,13 @@ impl<'a> ConvertESMExportsForHmr<'a> {
// no setter is added since live bindings are read-only
} else {
// 'abc,'
let key = Expr::init(
E::EString::init(export_symbol_name.unwrap_or(original_name).slice()),
loc,
);
self.export_props.push(G::Property {
key: Some(Expr::init(
E::EString::init(export_symbol_name.unwrap_or(original_name).slice()),
loc,
)),
flags: E::own_key_property_flags(&key),
key: Some(key),
value: Some(id),
..Default::default()
});
Expand Down
142 changes: 72 additions & 70 deletions src/js_printer/lib.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -951,6 +951,25 @@ where
b'"'
}

/// A `__proto__` key keeps its parsed form: `{ __proto__: x }` sets the prototype, `{ __proto__ }` is an own property.
fn can_use_shorthand_property(
key: &js_ast::e::String,
name: &[u8],
flags: js_ast::flags::PropertySet,
) -> bool {
key.eql_bytes(name)
&& (!key.eql_comptime(b"__proto__")
|| flags.contains(js_ast::flags::Property::WasShorthand))
}

/// `["__proto__"]: x` is the only own-property form left once the shorthand value was renamed.
fn must_print_proto_key_as_computed(
key: &js_ast::e::String,
flags: js_ast::flags::PropertySet,
) -> bool {
flags.contains(js_ast::flags::Property::WasShorthand) && key.eql_comptime(b"__proto__")
}

#[derive(Clone, Copy)]
pub struct Whitespacer {
pub normal: &'static [u8],
Expand Down Expand Up @@ -4828,6 +4847,26 @@ pub(crate) mod __gated_printer {
}
}

/// The identifier a property value prints as, if it prints as a bare identifier.
fn shorthand_value_name(&mut self, item: &G::Property) -> Option<&'a [u8]> {
match &item.value.as_ref()?.data {
ExprData::EIdentifier(e) => Some(self.name_for_symbol(e.ref_)),
ExprData::EImportIdentifier(e) => {
if self.options.input_files_for_dev_server.is_some() {
return None;
}
// Make sure we're not using a property access instead of an identifier
let ref_ = self.symbols().follow(e.ref_);
let symbol = self.symbols().get_const(ref_)?;
if symbol.namespace_alias.is_some() {
return None;
}
Some(self.name_for_symbol(e.ref_))
}
_ => None,
}
}

pub(crate) fn print_property(&mut self, item_in: &G::Property) {
// `G::Property` isn't `Copy`, so take a borrow and shallow-copy the
// mutable bits we may rewrite (key + flags).
Expand Down Expand Up @@ -4996,88 +5035,51 @@ pub(crate) mod __gated_printer {
self.add_source_mapping(key.loc);
if key_str.is_utf8() {
self.print_space_before_identifier();
let mut allow_shorthand = true;
if !IS_JSON && lexer::is_identifier(key_str.slice8()) {
self.print_identifier(key_str.slice8());
} else {
allow_shorthand = false;
self.print_string_literal_e_string(&key_str, false);
}

// Use a shorthand property if the names are the same
if let Some(val) = &item.value {
match &val.data {
ExprData::EIdentifier(e) => {
if key_str.slice8() == self.name_for_symbol(e.ref_) {
if let Some(initial) = &item.initializer {
self.print_initializer(*initial);
}
if allow_shorthand {
return;
}
}
}
ExprData::EImportIdentifier(e) => 'inner: {
let ref_ = self.symbols().follow(e.ref_);
if self.options.input_files_for_dev_server.is_some() {
break 'inner;
}
if let Some(symbol) = self.symbols().get_const(ref_) {
if symbol.namespace_alias.is_none()
&& key_str.slice8() == self.name_for_symbol(e.ref_)
{
if let Some(initial) = &item.initializer {
self.print_initializer(*initial);
}
if allow_shorthand {
return;
}
}
// Use a shorthand property if the names are the same
if let Some(name) = self.shorthand_value_name(&item) {
if can_use_shorthand_property(&key_str, name, item.flags) {
self.print_identifier(key_str.slice8());
if let Some(initial) = &item.initializer {
self.print_initializer(*initial);
}
return;
}
_ => {}
}

if must_print_proto_key_as_computed(&key_str, item.flags) {
self.print(b"[");
self.print_string_literal_e_string(&key_str, false);
self.print(b"]");
} else {
self.print_identifier(key_str.slice8());
}
} else {
self.print_string_literal_e_string(&key_str, false);
}
} else if !IS_JSON && self.can_print_identifier_utf16(key_str.slice16()) {
self.print_space_before_identifier();
self.print_identifier_utf16(key_str.slice16())
.expect("unreachable");

// Use a shorthand property if the names are the same
if let Some(val) = &item.value {
match &val.data {
ExprData::EIdentifier(e) => {
if item.flags.contains(js_ast::flags::Property::WasShorthand)
|| strings::utf16_eql_string(
key_str.slice16(),
self.name_for_symbol(e.ref_),
)
{
if let Some(initial) = &item.initializer {
self.print_initializer(*initial);
}
return;
}
if let Some(name) = self.shorthand_value_name(&item) {
if can_use_shorthand_property(&key_str, name, item.flags) {
self.print_identifier_utf16(key_str.slice16())
.expect("unreachable");
if let Some(initial) = &item.initializer {
self.print_initializer(*initial);
}
ExprData::EImportIdentifier(e) => {
let ref_ = self.symbols().follow(e.ref_);
if let Some(symbol) = self.symbols().get_const(ref_) {
if symbol.namespace_alias.is_none()
&& strings::utf16_eql_string(
key_str.slice16(),
self.name_for_symbol(e.ref_),
)
{
if let Some(initial) = &item.initializer {
self.print_initializer(*initial);
}
return;
}
}
}
_ => {}
return;
}
}

if must_print_proto_key_as_computed(&key_str, item.flags) {
self.print(b"[");
self.print_string_literal_e_string(&key_str, false);
self.print(b"]");
} else {
self.print_identifier_utf16(key_str.slice16())
.expect("unreachable");
}
} else {
let c = best_quote_char_for_string(key_str.slice16(), false);
self.print(c);
Expand Down
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