Skip to content

js_parser: don't fold wrappers that expose anonymous class/fn to NamedEvaluation #35593

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Closed
robobun wants to merge 4 commits into from
Closed

js_parser: don't fold wrappers that expose anonymous class/fn to NamedEvaluation #35593

Show file tree
Hide file tree
Changes from all commits
Commits
Show all changes
4 commits
Select commit Hold shift + click to select a range
3758bcc
js_parser: don't fold wrappers that expose anonymous class/fn to Name…
robobun Jul 25, 2026
ce4639e
Also guard left-operand folds and ternary CouldHaveSideEffects path
robobun Jul 25, 2026
99bed96
Trim inline comments per comment-cop
robobun Jul 25, 2026
aadf954
ci: retrigger
robobun Jul 25, 2026
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
2 changes: 2 additions & 0 deletions src/js_parser/fold.rs
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -483,6 +483,8 @@ impl<'a, const TYPESCRIPT: bool, const SCAN_ONLY: bool> P<'a, TYPESCRIPT, SCAN_O
name,
)
&& name != b"__proto__"
// "({ f: class {} }).f" => keep; name is "f" per spec
&& !value.is_anonymous_named()
{
return Some(value);
}
Expand Down
57 changes: 47 additions & 10 deletions src/js_parser/visit/visit_binary.rs
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -203,6 +203,7 @@ impl BinaryExpressionVisitor {
// "(sideEffects(), 2)" => "(sideEffects(), 2)"
// "(0, this.fn)" => "this.fn"
// "(0, this.fn)()" => "(0, this.fn)()"
// "(0, class {})" => "(0, class {})"
if p.options.features.minify_syntax {
// If e_.left is itself a comma, its .left was already simplified
// by the previous unwind step; only simplify its .right to avoid
Expand All @@ -221,14 +222,21 @@ impl BinaryExpressionVisitor {
};
if let Some(simplified_left) = simplified_left {
if simplified_left.is_empty() {
return e_.right;
if e_.right.is_anonymous_named() {
e_.left = Expr {
data: prefill::data::ZERO,
loc: e_.left.loc,
};
} else {
return e_.right;
}
} else {
e_.left = simplified_left;
}
e_.left = simplified_left;
} else {
// The left operand has no side effects, but we need to preserve
// the comma operator semantics when used as a call target
if is_call_target && e_.right.has_value_for_this_in_call() {
// Keep the comma expression to strip "this" binding
if (is_call_target && e_.right.has_value_for_this_in_call())
|| e_.right.is_anonymous_named()
{
e_.left = Expr {
data: prefill::data::ZERO,
loc: e_.left.loc,
Expand Down Expand Up @@ -366,12 +374,25 @@ impl BinaryExpressionVisitor {
let null_or_undefined = SideEffects::to_null_or_undefined(p, &e_.left.data);
if null_or_undefined.ok {
if !null_or_undefined.value {
// "(class {} ?? 0)" => "(0, class {})"
if e_.left.is_anonymous_named() {
return Expr::join_with_comma(
Expr {
data: prefill::data::ZERO,
loc: e_.left.loc,
},
e_.left,
);
}
return e_.left;
} else if null_or_undefined.side_effects == SideEffects::NoSideEffects {
// "(null ?? fn)()" => "fn()"
// "(null ?? this.fn)" => "this.fn"
// "(null ?? this.fn)()" => "(0, this.fn)()"
if is_call_target && e_.right.has_value_for_this_in_call() {
// "(null ?? class {})" => "(0, class {})"
if (is_call_target && e_.right.has_value_for_this_in_call())
|| e_.right.is_anonymous_named()
{
return Expr::join_with_comma(
Expr {
data: ExprData::ENumber(E::Number::new(0.0)),
Expand All @@ -388,13 +409,26 @@ impl BinaryExpressionVisitor {
Op::Code::BinLogicalOr => {
let side_effects = SideEffects::to_boolean(p, &e_.left.data);
if side_effects.ok && side_effects.value {
// "(class {} || 0)" => "(0, class {})"
if e_.left.is_anonymous_named() {
return Expr::join_with_comma(
Expr {
data: prefill::data::ZERO,
loc: e_.left.loc,
},
e_.left,
);
}
return e_.left;
} else if side_effects.ok && side_effects.side_effects == SideEffects::NoSideEffects
{
// "(0 || fn)()" => "fn()"
// "(0 || this.fn)" => "this.fn"
// "(0 || this.fn)()" => "(0, this.fn)()"
if is_call_target && e_.right.has_value_for_this_in_call() {
// "(0 || class {})" => "(0, class {})"
if (is_call_target && e_.right.has_value_for_this_in_call())
|| e_.right.is_anonymous_named()
{
return Expr::join_with_comma(
Expr {
data: prefill::data::ZERO,
Expand All @@ -416,7 +450,10 @@ impl BinaryExpressionVisitor {
// "(1 && fn)()" => "fn()"
// "(1 && this.fn)" => "this.fn"
// "(1 && this.fn)()" => "(0, this.fn)()"
if is_call_target && e_.right.has_value_for_this_in_call() {
// "(1 && class {})" => "(0, class {})"
if (is_call_target && e_.right.has_value_for_this_in_call())
|| e_.right.is_anonymous_named()
{
return Expr::join_with_comma(
Expr {
data: prefill::data::ZERO,
Expand Down Expand Up @@ -712,7 +749,7 @@ impl BinaryExpressionVisitor {
if let Some(dot) = e_.left.data.e_dot() {
if let Some(obj) = dot.target.data.e_object() {
if obj.properties.len_u32() == 0 {
if dot.name != b"__proto__" {
if dot.name != b"__proto__" && !e_.right.is_anonymous_named() {
return e_.right;
}
}
Expand Down
51 changes: 41 additions & 10 deletions src/js_parser/visit/visit_expr.rs
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -1091,7 +1091,16 @@ impl<'a, const TYPESCRIPT: bool, const SCAN_ONLY: bool> P<'a, TYPESCRIPT, SCAN_O
if array.items.len_u32() == 1 && number.value() == 0.0 {
let inlined = *array.items.at(0);
if inlined.can_be_inlined_from_property_access() {
*e = inlined;
// [class {}][0] -> (0, class {})
*e = if inlined.is_anonymous_named() {
Expr {
data: prefill::data::ZERO,
loc: expr.loc,
}
.join_with_comma(inlined)
} else {
inlined
};
return;
}
}
Expand All @@ -1108,7 +1117,15 @@ impl<'a, const TYPESCRIPT: bool, const SCAN_ONLY: bool> P<'a, TYPESCRIPT, SCAN_O
return;
}
debug_assert!(inlined.can_be_inlined_from_property_access());
*e = inlined;
*e = if inlined.is_anonymous_named() {
Expr {
data: prefill::data::ZERO,
loc: expr.loc,
}
.join_with_comma(inlined)
} else {
inlined
};
return;
}
}
Expand Down Expand Up @@ -1484,17 +1501,24 @@ impl<'a, const TYPESCRIPT: bool, const SCAN_ONLY: bool> P<'a, TYPESCRIPT, SCAN_O
p.visit_expr(&mut e_.no);
p.is_control_flow_dead = old;

// "(1 ? fn : 2)()" => "fn()"
// "(1 ? this.fn : 2)" => "this.fn"
// "(1 ? this.fn : 2)()" => "(0, this.fn)()"
// "(1 ? class {} : 2)" => "(0, class {})"
let needs_comma_wrap = (is_call_target && e_.yes.has_value_for_this_in_call())
|| e_.yes.is_anonymous_named();

if side_effects.side_effects == SideEffects::CouldHaveSideEffects {
*e = SideEffects::simplify_unused_expr(p, e_.test_)
.or_else(|| {
needs_comma_wrap.then(|| p.new_expr(E::Number::new(0.0), e_.test_.loc))
})
.unwrap_or_else(|| p.new_expr(E::Missing {}, e_.test_.loc))
.join_with_comma(e_.yes);
return;
}

// "(1 ? fn : 2)()" => "fn()"
// "(1 ? this.fn : 2)" => "this.fn"
// "(1 ? this.fn : 2)()" => "(0, this.fn)()"
if is_call_target && e_.yes.has_value_for_this_in_call() {
if needs_comma_wrap {
*e = p
.new_expr(E::Number::new(0.0), e_.test_.loc)
.join_with_comma(e_.yes);
Expand All @@ -1511,18 +1535,25 @@ impl<'a, const TYPESCRIPT: bool, const SCAN_ONLY: bool> P<'a, TYPESCRIPT, SCAN_O
p.is_control_flow_dead = old;
p.visit_expr(&mut e_.no);

// "(1 ? fn : 2)()" => "fn()"
// "(1 ? this.fn : 2)" => "this.fn"
// "(1 ? this.fn : 2)()" => "(0, this.fn)()"
// "(0 ? 1 : class {})" => "(0, class {})"
let needs_comma_wrap = (is_call_target && e_.no.has_value_for_this_in_call())
|| e_.no.is_anonymous_named();

// "(a, false) ? b : c" => "a, c"
if side_effects.side_effects == SideEffects::CouldHaveSideEffects {
*e = SideEffects::simplify_unused_expr(p, e_.test_)
.or_else(|| {
needs_comma_wrap.then(|| p.new_expr(E::Number::new(0.0), e_.test_.loc))
})
.unwrap_or_else(|| p.new_expr(E::Missing {}, e_.test_.loc))
.join_with_comma(e_.no);
return;
}

// "(1 ? fn : 2)()" => "fn()"
// "(1 ? this.fn : 2)" => "this.fn"
// "(1 ? this.fn : 2)()" => "(0, this.fn)()"
if is_call_target && e_.no.has_value_for_this_in_call() {
if needs_comma_wrap {
*e = p
.new_expr(E::Number::new(0.0), e_.test_.loc)
.join_with_comma(e_.no);
Expand Down
80 changes: 80 additions & 0 deletions test/bundler/transpiler/runtime-transpiler.test.ts
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -252,3 +252,83 @@ describe("unterminated string literals in large files", () => {
expect(exitCode).toBe(1);
});
});

describe("constant folding preserves NamedEvaluation semantics", () => {
// Folding a wrapper expression down to a bare anonymous class/function must
// not expose it to NamedEvaluation at the assignment/binding site.
test.concurrent("wrapped anonymous class/function .name stays empty", async () => {
const src = `
const A = (0, class {});
const B = true && class {};
const C = false || class {};
const D = null ?? class {};
const E = true ? class {} : 0;
const F = false ? 0 : class {};
const G = [class {}][0];
const H = [] ? class {} : 0;
const I = (function () {}) || 0;
const J = (() => {}) ?? 0;
const L = (class {}) ?? 0;
const fn = (0, function () {});
const ar = (0, () => {});
function param(P = (0, class {})) { return P.name; }
class Holder { field = (0, class {}); }
console.log(JSON.stringify({
A: A.name, B: B.name, C: C.name, D: D.name, E: E.name, F: F.name, G: G.name,
H: H.name, I: I.name, J: J.name, L: L.name,
fn: fn.name, ar: ar.name, param: param(), field: new Holder().field.name,
}));
`;
await using proc = Bun.spawn({ cmd: [bunExe(), "-e", src], env: bunEnv, stderr: "pipe" });
const [stdout, stderr, exitCode] = await Promise.all([proc.stdout.text(), proc.stderr.text(), proc.exited]);
expect(stderr).toBe("");
expect(JSON.parse(stdout)).toEqual({
A: "",
B: "",
C: "",
D: "",
E: "",
F: "",
G: "",
H: "",
I: "",
J: "",
L: "",
fn: "",
ar: "",
param: "",
field: "",
});
expect(exitCode).toBe(0);
});

test.concurrent("({ prop: class {} }).prop keeps the property key as .name", async () => {
const src = `
const K = ({ prop: class {} }).prop;
const M = ({ prop: function () {} }).prop;
const N = ({ prop: () => {} }).prop;
const X = ({}).x ??= class {};
console.log(JSON.stringify({ K: K.name, M: M.name, N: N.name, X: X.name }));
`;
await using proc = Bun.spawn({ cmd: [bunExe(), "-e", src], env: bunEnv, stderr: "pipe" });
const [stdout, stderr, exitCode] = await Promise.all([proc.stdout.text(), proc.stderr.text(), proc.exited]);
expect(stderr).toBe("");
expect(JSON.parse(stdout)).toEqual({ K: "prop", M: "prop", N: "prop", X: "" });
expect(exitCode).toBe(0);
});

test.concurrent("direct anonymous class/function still gets the binding name", async () => {
const src = `
const A = class {};
const B = function () {};
const C = () => {};
const D = (0, class Named {});
console.log(JSON.stringify({ A: A.name, B: B.name, C: C.name, D: D.name }));
`;
await using proc = Bun.spawn({ cmd: [bunExe(), "-e", src], env: bunEnv, stderr: "pipe" });
const [stdout, stderr, exitCode] = await Promise.all([proc.stdout.text(), proc.stderr.text(), proc.exited]);
expect(stderr).toBe("");
expect(JSON.parse(stdout)).toEqual({ A: "A", B: "B", C: "C", D: "Named" });
expect(exitCode).toBe(0);
});
});
Loading