fix(es/minifier): Force rename synthesized identifiers (#9473)

**Related issue:**

 - Closes https://github.com/swc-project/swc/issues/9468

.changeset/many-lobsters-knock.md

@@ -0,0 +1,6 @@
+---
+swc_ecma_minifier: patch
+swc_core: patch
+---
+
+fix(es/minifier): Force rename synthesized identifiers

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

@@ -2,11 +2,11 @@ use radix_fmt::Radix;
 use swc_common::{util::take::Take, Spanned, SyntaxContext};
 use swc_ecma_ast::*;
 use swc_ecma_utils::{number::ToJsString, ExprExt, IsEmpty, Value};
-#[cfg(feature = "debug")]
-use {crate::debug::dump, tracing::debug};
 
 use super::Pure;
 use crate::compress::util::{eval_as_number, is_pure_undefined_or_null};
+#[cfg(feature = "debug")]
+use crate::debug::dump;
 
 impl Pure<'_> {
     pub(super) fn eval_array_method_call(&mut self, e: &mut Expr) {
@@ -659,21 +659,15 @@ impl Pure<'_> {
             _ => return,
         };
 
-        #[cfg(feature = "debug")]
-        debug!(
-            "before: optimize_member_expr: {}",
-            dump(&*member_expr, false)
-        );
-
         if let Some(replacement) =
             self.optimize_member_expr(&mut member_expr.obj, &member_expr.prop)
         {
             *e = replacement;
             self.changed = true;
-            report_change!("member_expr: Optimized member expression");
-
-            #[cfg(feature = "debug")]
-            debug!("after: optimize_member_expr: {}", dump(&*e, false));
+            report_change!(
+                "member_expr: Optimized member expression as {}",
+                dump(&*e, false)
+            );
         }
     }
 

crates/swc_ecma_minifier/src/lib.rs

@@ -232,7 +232,7 @@ pub fn optimize(
         let _timer = timer!("mangle names");
         // TODO: base54.reset();
 
-        let preserved = idents_to_preserve(mangle.clone(), &n);
+        let preserved = idents_to_preserve(mangle.clone(), marks, &n);
 
         let chars = CharFreq::compute(
             &n,

crates/swc_ecma_minifier/src/pass/mangle_names/preserver.rs

@@ -1,26 +1,36 @@
 use rustc_hash::FxHashSet;
 use swc_ecma_ast::*;
+use swc_ecma_usage_analyzer::marks::Marks;
 use swc_ecma_utils::find_pat_ids;
 use swc_ecma_visit::{noop_visit_type, Visit, VisitWith};
 
 use crate::option::MangleOptions;
 
 /// Returns `(preserved, unresolved)`
-pub(crate) fn idents_to_preserve<N>(options: MangleOptions, n: &N) -> FxHashSet<Id>
+pub(crate) fn idents_to_preserve<N>(options: MangleOptions, marks: Marks, n: &N) -> FxHashSet<Id>
 where
-    N: VisitWith<Preserver>,
+    N: for<'a> VisitWith<Preserver<'a>>,
 {
     let mut v = Preserver {
-        options,
+        options: &options,
         preserved: Default::default(),
         should_preserve: false,
         in_top_level: false,
     };
     n.visit_with(&mut v);
+
+    let top_level_mark = marks.top_level_ctxt.outer();
+
+    // Force rename synthesized names
+    // See https://github.com/swc-project/swc/issues/9468
+    v.preserved.retain(|id| {
+        options.reserved.contains(&id.0) || id.1.outer().is_descendant_of(top_level_mark)
+    });
+
     v.preserved
 }
-pub(crate) struct Preserver {
-    options: MangleOptions,
+pub(crate) struct Preserver<'a> {
+    options: &'a MangleOptions,
 
     preserved: FxHashSet<Id>,
 
@@ -28,13 +38,13 @@ pub(crate) struct Preserver {
     in_top_level: bool,
 }
 
-impl Preserver {
+impl<'a> Preserver<'a> {
     fn is_reserved(&self, ident: &Ident) -> bool {
         self.options.reserved.contains(&ident.sym)
     }
 }
 
-impl Visit for Preserver {
+impl<'a> Visit for Preserver<'a> {
     noop_visit_type!();
 
     fn visit_block_stmt(&mut self, n: &BlockStmt) {

crates/swc_ecma_minifier/tests/fixture/issues/9468/input.js

@@ -0,0 +1,10 @@
+function func1(arg1, arg2) {
+    return getX(arg1) + arg2
+}
+function getX(x) {
+    const v = document.getElementById('eid').getAttribute(x)
+    return v
+}
+console.log(func1(7, getX('data-x')))
+console.log(func1(7, getX('data-y')))
+

crates/swc_ecma_minifier/tests/fixture/issues/9468/mangle.json

@@ -0,0 +1 @@
+{}

crates/swc_ecma_minifier/tests/fixture/issues/9468/output.js

@@ -0,0 +1,5 @@
+var t, e;
+function getX(t) {
+    return document.getElementById('eid').getAttribute(t);
+}
+console.log((t = getX('data-x'), getX(7) + t)), console.log((e = getX('data-y'), getX(7) + e));