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use swc_common::{util::take::Take, DUMMY_SP};
use swc_ecma_ast::*;
use swc_ecma_utils::{ExprFactory, StmtLike};
use super::Pure;
use crate::compress::util::is_pure_undefined;
impl Pure<'_> {
pub(super) fn drop_useless_ident_ref_in_seq(&mut self, seq: &mut SeqExpr) {
if !self.options.collapse_vars {
return;
}
if seq.exprs.len() < 2 {
return;
}
if let (Expr::Assign(assign @ AssignExpr { op: op!("="), .. }), Expr::Ident(ident)) = (
&*seq.exprs[seq.exprs.len() - 2],
&*seq.exprs[seq.exprs.len() - 1],
) {
// Check if lhs is same as `ident`.
if let AssignTarget::Simple(SimpleAssignTarget::Ident(left)) = &assign.left {
if left.id.sym == ident.sym && left.id.ctxt == ident.ctxt {
report_change!(
"drop_useless_ident_ref_in_seq: Dropping `{}` as it's useless",
left.id
);
self.changed = true;
seq.exprs.pop();
}
}
}
}
///
/// - `(path += 'foo', path)` => `(path += 'foo')`
pub(super) fn shift_assignment(&mut self, e: &mut SeqExpr) {
if e.exprs.len() < 2 {
return;
}
if let Some(last) = e.exprs.last() {
let last_id = match &**last {
Expr::Ident(i) => i,
_ => return,
};
if let Expr::Assign(assign @ AssignExpr { op: op!("="), .. }) =
&*e.exprs[e.exprs.len() - 2]
{
if let Some(lhs) = assign.left.as_ident() {
if lhs.sym == last_id.sym && lhs.ctxt == last_id.ctxt {
e.exprs.pop();
self.changed = true;
report_change!("sequences: Shifting assignment");
}
};
}
}
}
pub(super) fn shift_void(&mut self, e: &mut SeqExpr) {
if e.exprs.len() < 2 {
return;
}
if let Expr::Unary(UnaryExpr {
op: op!("void"), ..
}) = &*e.exprs[e.exprs.len() - 2]
{
return;
}
if let Some(last) = e.exprs.last() {
if is_pure_undefined(self.expr_ctx, last) {
self.changed = true;
report_change!("sequences: Shifting void");
e.exprs.pop();
let last = e.exprs.last_mut().unwrap();
*last = UnaryExpr {
span: DUMMY_SP,
op: op!("void"),
arg: last.take(),
}
.into()
}
}
}
/// Break assignments in sequences.
///
/// This may result in less parenthesis.
pub(super) fn break_assignments_in_seqs<T>(&mut self, stmts: &mut Vec<T>)
where
T: StmtLike,
{
// TODO
if true {
return;
}
let need_work = stmts.iter().any(|stmt| match stmt.as_stmt() {
Some(Stmt::Expr(e)) => match &*e.expr {
Expr::Seq(seq) => {
seq.exprs.len() > 1
&& seq.exprs.iter().all(|expr| {
matches!(&**expr, Expr::Assign(AssignExpr { op: op!("="), .. }))
})
}
_ => false,
},
_ => false,
});
if !need_work {
return;
}
let mut new_stmts = Vec::new();
for stmt in stmts.take() {
match stmt.try_into_stmt() {
Ok(stmt) => match stmt {
Stmt::Expr(es)
if match &*es.expr {
Expr::Seq(seq) => {
seq.exprs.len() > 1
&& seq.exprs.iter().all(|expr| {
matches!(
&**expr,
Expr::Assign(AssignExpr { op: op!("="), .. })
)
})
}
_ => false,
} =>
{
let span = es.span;
let seq = es.expr.seq().unwrap();
new_stmts.extend(
seq.exprs
.into_iter()
.map(|expr| ExprStmt { span, expr })
.map(Stmt::Expr)
.map(T::from),
);
}
_ => {
new_stmts.push(T::from(stmt));
}
},
Err(stmt) => {
new_stmts.push(stmt);
}
}
}
self.changed = true;
report_change!(
"sequences: Splitted a sequence expression to multiple expression statements"
);
*stmts = new_stmts;
}
///
/// - `(a, b, c) && d` => `a, b, c && d`
pub(super) fn lift_seqs_of_bin(&mut self, e: &mut Expr) {
let bin = match e {
Expr::Bin(b) => b,
_ => return,
};
if let Expr::Seq(left) = &mut *bin.left {
if left.exprs.is_empty() {
return;
}
self.changed = true;
report_change!("sequences: Lifting sequence in a binary expression");
let left_last = left.exprs.pop().unwrap();
let mut exprs = left.exprs.take();
exprs.push(
BinExpr {
span: left.span,
op: bin.op,
left: left_last,
right: bin.right.take(),
}
.into(),
);
*e = SeqExpr {
span: bin.span,
exprs,
}
.into()
}
}
///
/// - `x = (foo(), bar(), baz()) ? 10 : 20` => `foo(), bar(), x = baz() ? 10
/// : 20;`
pub(super) fn lift_seqs_of_cond_assign(&mut self, e: &mut Expr) {
if !self.options.sequences() {
return;
}
let assign = match e {
Expr::Assign(v @ AssignExpr { op: op!("="), .. }) => v,
_ => return,
};
let cond = match &mut *assign.right {
Expr::Cond(v) => v,
_ => return,
};
if let Expr::Seq(test) = &mut *cond.test {
//
if test.exprs.len() >= 2 {
let mut new_seq = Vec::new();
new_seq.extend(test.exprs.drain(..test.exprs.len() - 1));
self.changed = true;
report_change!("sequences: Lifting sequences in a assignment with cond expr");
let new_cond = CondExpr {
span: cond.span,
test: test.exprs.pop().unwrap(),
cons: cond.cons.take(),
alt: cond.alt.take(),
};
new_seq.push(
AssignExpr {
span: assign.span,
op: assign.op,
left: assign.left.take(),
right: Box::new(new_cond.into()),
}
.into(),
);
*e = SeqExpr {
span: assign.span,
exprs: new_seq,
}
.into();
}
}
}
/// `(a = foo, a.apply())` => `(a = foo).apply()`
///
/// This is useful for outputs of swc/babel
pub(super) fn merge_seq_call(&mut self, e: &mut SeqExpr) {
if !self.options.sequences() {
return;
}
for idx in 0..e.exprs.len() {
let (e1, e2) = e.exprs.split_at_mut(idx);
let a = match e1.last_mut() {
Some(v) => &mut **v,
None => continue,
};
let b = match e2.first_mut() {
Some(v) => &mut **v,
None => continue,
};
if let (
Expr::Assign(a_assign @ AssignExpr { op: op!("="), .. }),
Expr::Call(CallExpr {
callee: Callee::Expr(b_callee),
args,
..
}),
) = (&mut *a, &mut *b)
{
let var_name = a_assign.left.as_ident();
let var_name = match var_name {
Some(v) => v,
None => continue,
};
match &mut **b_callee {
Expr::Member(MemberExpr {
obj: b_callee_obj,
prop,
..
}) if prop.is_ident_with("apply") || prop.is_ident_with("call") => {
//
if let Expr::Ident(b_callee_obj) = &**b_callee_obj {
if b_callee_obj.to_id() != var_name.to_id() {
continue;
}
} else {
continue;
}
let span = a_assign.span;
let obj = Box::new(a.take());
let new = CallExpr {
span,
callee: MemberExpr {
span: DUMMY_SP,
obj,
prop: prop.take(),
}
.as_callee(),
args: args.take(),
..Default::default()
}
.into();
b.take();
self.changed = true;
report_change!(
"sequences: Reducing `(a = foo, a.call())` to `((a = foo).call())`"
);
*a = new;
}
_ => (),
};
}
}
}
}