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feat(es/compiler): Merge nullish_coalescing #10974

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3a56eca
quick cleanup for refacotr
CodeMan62 Aug 14, 2025
8f5c54c
ref
CodeMan62 Sep 29, 2025
44aac8d
Merge branch 'main' into nullish_coalescing/compiler
CodeMan62 Sep 29, 2025
b0a03e3
fix CI
CodeMan62 Sep 29, 2025
bc98a9b
fix toml
CodeMan62 Sep 29, 2025
529a8a5
bump version
CodeMan62 Sep 29, 2025
cda8a76
fmt
CodeMan62 Sep 29, 2025
ad5e6e4
clippy
CodeMan62 Sep 29, 2025
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2 changes: 2 additions & 0 deletions Cargo.lock
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3 changes: 1 addition & 2 deletions crates/swc_ecma_compat_es2020/src/lib.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -18,10 +18,9 @@ pub fn es2020(config: Config, unresolved_mark: Mark) -> impl Pass {
assumptions.no_document_all = config.nullish_coalescing.no_document_all;

(
nullish_coalescing(config.nullish_coalescing),
optional_chaining(config.optional_chaining, unresolved_mark),
Compiler::new(swc_ecma_compiler::Config {
includes: Features::EXPORT_NAMESPACE_FROM,
includes: Features::EXPORT_NAMESPACE_FROM | Features::NULLISH_COALESCING,
assumptions,
..Default::default()
}),
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275 changes: 13 additions & 262 deletions crates/swc_ecma_compat_es2020/src/nullish_coalescing.rs
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Original file line number Diff line number Diff line change
@@ -1,264 +1,15 @@
use std::mem::take;

use serde::Deserialize;
use swc_common::{util::take::Take, Span, DUMMY_SP};
use swc_ecma_ast::*;
use swc_ecma_utils::{alias_ident_for_simple_assign_tatget, alias_if_required, StmtLike};
use swc_ecma_visit::{noop_visit_mut_type, visit_mut_pass, VisitMut, VisitMutWith};

pub fn nullish_coalescing(c: Config) -> impl Pass + 'static {
visit_mut_pass(NullishCoalescing {
c,
..Default::default()
use swc_ecma_ast::Pass;
pub use swc_ecma_compiler::es2020::nullish_coalescing::Config;
use swc_ecma_compiler::{Compiler, Features};
use swc_ecma_transforms_base::assumptions::Assumptions;

pub fn nullish_coalescing(c: Config) -> impl Pass {
let mut assumptions = Assumptions::default();
assumptions.no_document_all = c.no_document_all;

Compiler::new(swc_ecma_compiler::Config {
includes: Features::NULLISH_COALESCING,
excludes: Features::empty(),
assumptions,
})
}

#[derive(Debug, Default)]
struct NullishCoalescing {
vars: Vec<VarDeclarator>,
c: Config,
}

#[derive(Debug, Clone, Copy, Default, Deserialize)]
#[serde(rename_all = "camelCase")]
pub struct Config {
#[serde(default)]
pub no_document_all: bool,
}

impl NullishCoalescing {
fn visit_mut_stmt_like<T>(&mut self, stmts: &mut Vec<T>)
where
T: VisitMutWith<Self> + StmtLike,
{
let mut buf = Vec::with_capacity(stmts.len() + 2);

for mut stmt in stmts.take() {
stmt.visit_mut_with(self);

if !self.vars.is_empty() {
buf.push(T::from(
VarDecl {
span: DUMMY_SP,
kind: VarDeclKind::Var,
decls: take(&mut self.vars),
declare: false,
..Default::default()
}
.into(),
));
}

buf.push(stmt);
}

*stmts = buf
}
}

impl VisitMut for NullishCoalescing {
noop_visit_mut_type!(fail);

/// Prevents #1123
fn visit_mut_block_stmt(&mut self, s: &mut BlockStmt) {
let old_vars = self.vars.take();
s.visit_mut_children_with(self);
self.vars = old_vars;
}

/// Prevents #1123
fn visit_mut_switch_case(&mut self, s: &mut SwitchCase) {
// Prevents #6328
s.test.visit_mut_with(self);
let old_vars = self.vars.take();
s.cons.visit_mut_with(self);
self.vars = old_vars;
}

fn visit_mut_module_items(&mut self, n: &mut Vec<ModuleItem>) {
self.visit_mut_stmt_like(n)
}

fn visit_mut_stmts(&mut self, n: &mut Vec<Stmt>) {
self.visit_mut_stmt_like(n)
}

fn visit_mut_expr(&mut self, e: &mut Expr) {
e.visit_mut_children_with(self);

match e {
Expr::Bin(BinExpr {
span,
left,
op: op!("??"),
right,
}) => {
//
let (l, aliased) = alias_if_required(left, "ref");

if aliased {
self.vars.push(VarDeclarator {
span: DUMMY_SP,
name: l.clone().into(),
init: None,
definite: false,
});
}

let var_expr = if aliased {
AssignExpr {
span: DUMMY_SP,
op: op!("="),
left: l.clone().into(),
right: left.take(),
}
.into()
} else {
l.clone().into()
};

*e = make_cond(self.c, *span, &l, var_expr, right.take());
}

Expr::Assign(ref mut assign @ AssignExpr { op: op!("??="), .. }) => {
match &mut assign.left {
AssignTarget::Simple(SimpleAssignTarget::Ident(i)) => {
*e = AssignExpr {
span: assign.span,
op: op!("="),
left: i.clone().into(),
right: Box::new(make_cond(
self.c,
assign.span,
&Ident::from(&*i),
Expr::Ident(Ident::from(&*i)),
assign.right.take(),
)),
}
.into();
}

AssignTarget::Simple(left) => {
let alias = alias_ident_for_simple_assign_tatget(left, "refs");
self.vars.push(VarDeclarator {
span: DUMMY_SP,
name: alias.clone().into(),
init: None,
definite: false,
});

// TODO: Check for computed.
let right_expr = AssignExpr {
span: assign.span,
left: left.clone().into(),
op: op!("="),
right: assign.right.take(),
}
.into();

let var_expr = AssignExpr {
span: DUMMY_SP,
op: op!("="),
left: alias.clone().into(),
right: left.take().into(),
}
.into();

*e = AssignExpr {
span: assign.span,
op: op!("="),
left: alias.clone().into(),
right: Box::new(make_cond(
self.c,
assign.span,
&alias,
var_expr,
right_expr,
)),
}
.into();
}

_ => {}
}
}

_ => {}
}
}

fn visit_mut_block_stmt_or_expr(&mut self, n: &mut BlockStmtOrExpr) {
let vars = self.vars.take();
n.visit_mut_children_with(self);

if !self.vars.is_empty() {
if let BlockStmtOrExpr::Expr(expr) = n {
// expr
// { var decl = init; return expr; }
let stmts = vec![
VarDecl {
span: DUMMY_SP,
kind: VarDeclKind::Var,
decls: self.vars.take(),
declare: false,
..Default::default()
}
.into(),
Stmt::Return(ReturnStmt {
span: DUMMY_SP,
arg: Some(expr.take()),
}),
];
*n = BlockStmtOrExpr::BlockStmt(BlockStmt {
span: DUMMY_SP,
stmts,
..Default::default()
});
}
}

self.vars = vars;
}
}

#[tracing::instrument(level = "debug", skip_all)]
fn make_cond(c: Config, span: Span, alias: &Ident, var_expr: Expr, init: Box<Expr>) -> Expr {
if c.no_document_all {
CondExpr {
span,
test: BinExpr {
span: DUMMY_SP,
left: Box::new(var_expr),
op: op!("!="),
right: Box::new(Expr::Lit(Lit::Null(Null { span: DUMMY_SP }))),
}
.into(),
cons: alias.clone().into(),
alt: init,
}
} else {
CondExpr {
span,
test: BinExpr {
span: DUMMY_SP,
left: Box::new(Expr::Bin(BinExpr {
span: DUMMY_SP,
left: Box::new(var_expr),
op: op!("!=="),
right: Box::new(Expr::Lit(Lit::Null(Null { span: DUMMY_SP }))),
})),
op: op!("&&"),
right: Box::new(Expr::Bin(BinExpr {
span: DUMMY_SP,
left: Box::new(Expr::Ident(alias.clone())),
op: op!("!=="),
right: Expr::undefined(DUMMY_SP),
})),
}
.into(),
cons: alias.clone().into(),
alt: init,
}
}
.into()
}
1 change: 1 addition & 0 deletions crates/swc_ecma_compiler/Cargo.toml
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Original file line number Diff line number Diff line change
Expand Up @@ -12,6 +12,7 @@ version = "5.0.0"
[dependencies]
bitflags = { workspace = true }
rustc-hash = { workspace = true }
serde = { workspace = true }
tracing = { workspace = true }

swc_atoms = { version = "7.0.0", path = "../swc_atoms" }
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1 change: 1 addition & 0 deletions crates/swc_ecma_compiler/src/es2020/mod.rs
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Original file line number Diff line number Diff line change
@@ -1 +1,2 @@
pub(crate) mod export_namespace_from;
pub mod nullish_coalescing;
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