fix(es/minifier): Preserve flags while dropping elements of SeqExpr

.changeset/gorgeous-ties-fail.md

@@ -0,0 +1,5 @@
+---
+swc_ecma_minifier: patch
+---
+
+dead_branch_remover removes PURE annotations on sequence expressions

Cargo.toml

@@ -66,6 +66,7 @@ resolver = "2"
  copyless = "0.1.5"
  crc = "2.1.0"
  criterion = "0.5.1"
+ crossbeam-queue = "0.3.11"
  dashmap = "5.5.3"
  dialoguer = "0.10.2"
  difference = "2"

crates/swc_ecma_minifier/Cargo.toml

@@ -51,6 +51,7 @@ serde = { workspace = true, features = ["derive"] }
 serde_json = { workspace = true }
 tracing = { workspace = true }
 
+
 swc_allocator = { version = "0.1.7", path = "../swc_allocator", default-features = false }
 swc_atoms = { version = "0.6.5", path = "../swc_atoms" }
 swc_common = { version = "0.36.0", path = "../swc_common" }

crates/swc_ecma_minifier/src/compress/mod.rs

@@ -235,7 +235,6 @@ impl Compressor<'_> {
 
  let mut visitor = pure_optimizer(
  self.options,
- None,
  self.marks,
  PureOptimizerConfig {
  enable_join_vars: self.pass > 1,

crates/swc_ecma_minifier/src/compress/optimize/mod.rs

@@ -1817,7 +1817,9 @@ impl VisitMut for Optimizer<'_> {
 
  match e {
  Expr::Seq(seq) if seq.exprs.len() == 1 => {
+ let span = seq.span;
  *e = *seq.exprs[0].take();
+ e.set_span(span);
  }
 
  Expr::Assign(AssignExpr {

crates/swc_ecma_minifier/src/compress/pure/misc.rs

@@ -870,7 +870,11 @@ impl Pure<'_> {
  }
  }
 
- fn make_ignored_expr(&mut self, exprs: impl Iterator<Item = Box<Expr>>) -> Option<Expr> {
+ fn make_ignored_expr(
+ &mut self,
+ span: Span,
+ exprs: impl Iterator<Item = Box<Expr>>,
+ ) -> Option<Expr> {
  let mut exprs = exprs
  .filter_map(|mut e| {
  self.ignore_return_value(
@@ -894,7 +898,9 @@ impl Pure<'_> {
  return None;
  }
  if exprs.len() == 1 {
- return Some(*exprs.remove(0));
+ let mut new = *exprs.remove(0);
+ new.set_span(span);
+ return Some(new);
  }
 
  Some(
@@ -970,32 +976,41 @@ impl Pure<'_> {
  }
  }
 
- Expr::Call(CallExpr { ctxt, args, .. }) if ctxt.has_mark(self.marks.pure) => {
+ Expr::Call(CallExpr {
+ span, ctxt, args, ..
+ }) if ctxt.has_mark(self.marks.pure) => {
  report_change!("ignore_return_value: Dropping a pure call");
  self.changed = true;
 
- let new = self.make_ignored_expr(args.take().into_iter().map(|arg| arg.expr));
+ let new =
+ self.make_ignored_expr(*span, args.take().into_iter().map(|arg| arg.expr));
 
  *e = new.unwrap_or(Invalid { span: DUMMY_SP }.into());
  return;
  }
 
- Expr::TaggedTpl(TaggedTpl { ctxt, tpl, .. }) if ctxt.has_mark(self.marks.pure) => {
+ Expr::TaggedTpl(TaggedTpl {
+ span, ctxt, tpl, ..
+ }) if ctxt.has_mark(self.marks.pure) => {
  report_change!("ignore_return_value: Dropping a pure call");
  self.changed = true;
 
- let new = self.make_ignored_expr(tpl.exprs.take().into_iter());
+ let new = self.make_ignored_expr(*span, tpl.exprs.take().into_iter());
 
  *e = new.unwrap_or(Invalid { span: DUMMY_SP }.into());
  return;
  }
 
- Expr::New(NewExpr { ctxt, args, .. }) if ctxt.has_mark(self.marks.pure) => {
+ Expr::New(NewExpr {
+ span, ctxt, args, ..
+ }) if ctxt.has_mark(self.marks.pure) => {
  report_change!("ignore_return_value: Dropping a pure call");
  self.changed = true;
 
- let new =
- self.make_ignored_expr(args.take().into_iter().flatten().map(|arg| arg.expr));
+ let new = self.make_ignored_expr(
+ *span,
+ args.take().into_iter().flatten().map(|arg| arg.expr),
+ );
 
  *e = new.unwrap_or(Invalid { span: DUMMY_SP }.into());
  return;
@@ -1006,6 +1021,7 @@ impl Pure<'_> {
 
  match e {
  Expr::Call(CallExpr {
+ span,
  callee: Callee::Expr(callee),
  args,
  ..
@@ -1014,20 +1030,23 @@ impl Pure<'_> {
  self.changed = true;
  report_change!("Dropping pure call as callee is pure");
  *e = self
- .make_ignored_expr(args.take().into_iter().map(|arg| arg.expr))
+ .make_ignored_expr(*span, args.take().into_iter().map(|arg| arg.expr))
  .unwrap_or(Invalid { span: DUMMY_SP }.into());
  return;
  }
  }
 
  Expr::TaggedTpl(TaggedTpl {
- tag: callee, tpl, ..
+ span,
+ tag: callee,
+ tpl,
+ ..
  }) => {
  if callee.is_pure_callee(&self.expr_ctx) {
  self.changed = true;
  report_change!("Dropping pure tag tpl as callee is pure");
  *e = self
- .make_ignored_expr(tpl.exprs.take().into_iter())
+ .make_ignored_expr(*span, tpl.exprs.take().into_iter())
  .unwrap_or(Invalid { span: DUMMY_SP }.into());
  return;
  }
@@ -1357,24 +1376,29 @@ impl Pure<'_> {
 
  if self.options.side_effects && self.options.pristine_globals {
  match e {
- Expr::New(NewExpr { callee, args, .. })
- if callee.is_one_of_global_ref_to(
- &self.expr_ctx,
- &[
- "Map", "Set", "Array", "Object", "Boolean", "Number", "String",
- ],
- ) =>
+ Expr::New(NewExpr {
+ span, callee, args, ..
+ }) if callee.is_one_of_global_ref_to(
+ &self.expr_ctx,
+ &[
+ "Map", "Set", "Array", "Object", "Boolean", "Number", "String",
+ ],
+ ) =>
  {
  report_change!("Dropping a pure new expression");
 
  self.changed = true;
  *e = self
- .make_ignored_expr(args.iter_mut().flatten().map(|arg| arg.expr.take()))
+ .make_ignored_expr(
+ *span,
+ args.iter_mut().flatten().map(|arg| arg.expr.take()),
+ )
  .unwrap_or(Invalid { span: DUMMY_SP }.into());
  return;
  }
 
  Expr::Call(CallExpr {
+ span,
  callee: Callee::Expr(callee),
  args,
  ..
@@ -1387,7 +1411,7 @@ impl Pure<'_> {
 
  self.changed = true;
  *e = self
- .make_ignored_expr(args.iter_mut().map(|arg| arg.expr.take()))
+ .make_ignored_expr(*span, args.iter_mut().map(|arg| arg.expr.take()))
  .unwrap_or(Invalid { span: DUMMY_SP }.into());
  return;
  }
@@ -1427,7 +1451,7 @@ impl Pure<'_> {
  }
 
  *e = self
- .make_ignored_expr(exprs.into_iter())
+ .make_ignored_expr(obj.span, exprs.into_iter())
  .unwrap_or(Invalid { span: DUMMY_SP }.into());
  report_change!("Ignored an object literal");
  self.changed = true;
@@ -1499,7 +1523,7 @@ impl Pure<'_> {
  }
 
  *e = self
- .make_ignored_expr(exprs.into_iter())
+ .make_ignored_expr(arr.span, exprs.into_iter())
  .unwrap_or(Invalid { span: DUMMY_SP }.into());
  report_change!("Ignored an array literal");
  self.changed = true;
@@ -1514,6 +1538,7 @@ impl Pure<'_> {
  //
  // foo(),basr(),foo;
  Expr::Member(MemberExpr {
+ span,
  obj,
  prop: MemberProp::Computed(prop),
  ..
@@ -1526,6 +1551,7 @@ impl Pure<'_> {
  _ => {
  *e = self
  .make_ignored_expr(
+ *span,
  vec![obj.take(), prop.expr.take()].into_iter(),
  )
  .unwrap_or(Invalid { span: DUMMY_SP }.into());

crates/swc_ecma_minifier/src/compress/pure/mod.rs

@@ -15,10 +15,7 @@ use self::{ctx::Ctx, misc::DropOpts};
 use super::util::is_pure_undefined_or_null;
 #[cfg(feature = "debug")]
 use crate::debug::dump;
-use crate::{
- debug::AssertValid, maybe_par, option::CompressOptions, program_data::ProgramData,
- util::ModuleItemExt,
-};
+use crate::{debug::AssertValid, maybe_par, option::CompressOptions, util::ModuleItemExt};
 
 mod arrows;
 mod bools;
@@ -52,7 +49,6 @@ pub(crate) struct PureOptimizerConfig {
 #[allow(clippy::needless_lifetimes)]
 pub(crate) fn pure_optimizer<'a>(
  options: &'a CompressOptions,
- data: Option<&'a ProgramData>,
  marks: Marks,
  config: PureOptimizerConfig,
 ) -> impl 'a + VisitMut + Repeated {
@@ -64,7 +60,6 @@ pub(crate) fn pure_optimizer<'a>(
  unresolved_ctxt: SyntaxContext::empty().apply_mark(marks.unresolved_mark),
  is_unresolved_ref_safe: false,
  },
- data,
  ctx: Default::default(),
  changed: Default::default(),
  }
@@ -76,8 +71,6 @@ struct Pure<'a> {
  marks: Marks,
  expr_ctx: ExprCtx,
 
- #[allow(unused)]
- data: Option<&'a ProgramData>,
  ctx: Ctx,
  changed: bool,
 }

crates/swc_ecma_minifier/src/eval.rs

@@ -242,7 +242,6 @@ impl Evaluator {
  {
  e.visit_mut_with(&mut pure_optimizer(
  &Default::default(),
- None,
  self.marks,
  PureOptimizerConfig {
  enable_join_vars: false,

crates/swc_ecma_minifier/src/lib.rs

@@ -202,7 +202,6 @@ pub fn optimize(
 
  let mut v = pure_optimizer(
  c,
- None,
  marks,
  PureOptimizerConfig {
  force_str_for_tpl: Minification.force_str_for_tpl(),

crates/swc_ecma_minifier/tests/benches-full/terser.js

@@ -4437,8 +4437,7 @@
  let printed_comments = new Set();
  var to_utf8 = options.ascii_only ? function(str, identifier = !1, regexp = !1) {
  return !(options.ecma >= 2015) || options.safari10 || regexp || (str = str.replace(/[\ud800-\udbff][\udc00-\udfff]/g, function(ch) {
- return "\\u{" + // https://en.wikipedia.org/wiki/Universal_Character_Set_characters#Surrogates
- (is_surrogate_pair_head(ch.charCodeAt(0)) ? 0x10000 + (ch.charCodeAt(0) - 0xd800 << 10) + ch.charCodeAt(1) - 0xdc00 : ch.charCodeAt(0)).toString(16) + "}";
+ return "\\u{" + (is_surrogate_pair_head(ch.charCodeAt(0)) ? 0x10000 + (ch.charCodeAt(0) - 0xd800 << 10) + ch.charCodeAt(1) - 0xdc00 : ch.charCodeAt(0)).toString(16) + "}";
  })), str.replace(/[\u0000-\u001f\u007f-\uffff]/g, function(ch) {
  var code = ch.charCodeAt(0).toString(16);
  if (code.length <= 2 && !identifier) {

crates/swc_ecma_minifier/tests/benches-full/victory.js

@@ -11730,8 +11730,7 @@ object-assign
  // Equivalent of `typeof` but with special handling for array and regexp.
  function getPropType(propValue) {
  var propType = typeof propValue;
- return Array.isArray(propValue) ? 'array' : propValue instanceof RegExp ? 'object' : // Native Symbol.
- 'symbol' === propType || propValue && ('Symbol' === propValue['@@toStringTag'] || 'function' == typeof Symbol && propValue instanceof Symbol) ? 'symbol' : propType;
+ return Array.isArray(propValue) ? 'array' : propValue instanceof RegExp ? 'object' : 'symbol' === propType || propValue && ('Symbol' === propValue['@@toStringTag'] || 'function' == typeof Symbol && propValue instanceof Symbol) ? 'symbol' : propType;
  }
  // This handles more types than `getPropType`. Only used for error messages.
  // See `createPrimitiveTypeChecker`.