fix(es/minifier): Don't create names which is same as an unresolved var (#4806)

crates/swc_ecma_minifier/src/pass/mangle_names/analyzer/mod.rs

@@ -16,12 +16,21 @@ pub(super) struct Analyzer {
 }
 
 impl Analyzer {
-    pub(super) fn into_rename_map(mut self, preserved: &FxHashSet<Id>) -> AHashMap<Id, JsWord> {
+    pub(super) fn into_rename_map(
+        mut self,
+        preserved: &FxHashSet<Id>,
+        unresolved: &FxHashSet<JsWord>,
+    ) -> AHashMap<Id, JsWord> {
         let mut map = Default::default();
 
         self.scope.prepare_renaming();
 
-        let preserved_symbols = preserved.iter().cloned().map(|v| v.0).collect();
+        let mut preserved_symbols = preserved
+            .iter()
+            .cloned()
+            .map(|v| v.0)
+            .collect::<FxHashSet<_>>();
+        preserved_symbols.extend(unresolved.iter().cloned());
         self.scope
             .rename(&mut map, &Default::default(), preserved, &preserved_symbols);
 

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

@@ -1,26 +1,39 @@
 use rustc_hash::FxHashSet;
+use swc_atoms::JsWord;
+use swc_common::SyntaxContext;
 use swc_ecma_ast::*;
 use swc_ecma_utils::find_pat_ids;
 use swc_ecma_visit::{noop_visit_type, Visit, VisitWith};
 
 use crate::option::MangleOptions;
 
-pub(super) fn idents_to_preserve<N>(options: MangleOptions, n: &N) -> FxHashSet<Id>
+/// Returns `(preserved, unresolved)`
+pub(super) fn idents_to_preserve<N>(
+    options: MangleOptions,
+    unresolved_ctxt: SyntaxContext,
+    n: &N,
+) -> (FxHashSet<Id>, FxHashSet<JsWord>)
 where
     N: VisitWith<Preserver>,
 {
     let mut v = Preserver {
         options,
+        unresolved_ctxt,
         preserved: Default::default(),
+        unresolved: Default::default(),
         should_preserve: false,
         in_top_level: false,
     };
     n.visit_with(&mut v);
-    v.preserved
+    (v.preserved, v.unresolved)
 }
 pub(super) struct Preserver {
     options: MangleOptions,
+    unresolved_ctxt: SyntaxContext,
+
     preserved: FxHashSet<Id>,
+    unresolved: FxHashSet<JsWord>,
+
     should_preserve: bool,
     in_top_level: bool,
 }
@@ -116,6 +129,12 @@ impl Visit for Preserver {
         }
     }
 
+    fn visit_ident(&mut self, n: &Ident) {
+        if self.unresolved_ctxt == n.span.ctxt {
+            self.unresolved.insert(n.sym.clone());
+        }
+    }
+
     fn visit_module_items(&mut self, n: &[ModuleItem]) {
         for n in n {
             self.in_top_level = true;

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

@@ -1,6 +1,6 @@
 use rustc_hash::FxHashSet;
 use swc_atoms::JsWord;
-use swc_common::collections::AHashMap;
+use swc_common::{collections::AHashMap, SyntaxContext};
 use swc_ecma_ast::*;
 use swc_ecma_transforms_base::hygiene::rename;
 use swc_ecma_visit::{noop_visit_mut_type, VisitMut, VisitMutWith, VisitWith};
@@ -9,17 +9,22 @@ use tracing::info;
 use super::{analyzer::Analyzer, preserver::idents_to_preserve};
 use crate::{debug::dump, marks::Marks, option::MangleOptions, util::contains_eval};
 
-pub(crate) fn name_mangler(options: MangleOptions, _marks: Marks) -> impl VisitMut {
+pub(crate) fn name_mangler(options: MangleOptions, marks: Marks) -> impl VisitMut {
     Mangler {
         options,
+        unresolved_ctxt: SyntaxContext::empty().apply_mark(marks.unresolved_mark),
         preserved: Default::default(),
+        unresolved: Default::default(),
     }
 }
 
 struct Mangler {
     options: MangleOptions,
 
+    unresolved_ctxt: SyntaxContext,
+
     preserved: FxHashSet<Id>,
+    unresolved: FxHashSet<JsWord>,
 }
 
 impl Mangler {
@@ -33,7 +38,7 @@ impl Mangler {
         };
         node.visit_with(&mut analyzer);
 
-        analyzer.into_rename_map(&self.preserved)
+        analyzer.into_rename_map(&self.preserved, &self.unresolved)
     }
 }
 
@@ -75,7 +80,9 @@ impl VisitMut for Mangler {
     unit!(visit_mut_private_method, PrivateMethod);
 
     fn visit_mut_module(&mut self, m: &mut Module) {
-        self.preserved = idents_to_preserve(self.options.clone(), &*m);
+        let v = idents_to_preserve(self.options.clone(), self.unresolved_ctxt, &*m);
+        self.preserved = v.0;
+        self.unresolved = v.1;
 
         if option_env!("DEBUG_MANGLER") == Some("1") {
             info!("Before: {}", dump(&*m, true));
@@ -95,7 +102,9 @@ impl VisitMut for Mangler {
     }
 
     fn visit_mut_script(&mut self, s: &mut Script) {
-        self.preserved = idents_to_preserve(self.options.clone(), &*s);
+        let v = idents_to_preserve(self.options.clone(), self.unresolved_ctxt, &*s);
+        self.preserved = v.0;
+        self.unresolved = v.1;
 
         if contains_eval(s, true) {
             s.visit_mut_children_with(self);

crates/swc_ecma_minifier/tests/full/next-33088/output.js

@@ -1,12 +1,12 @@
-import*as a from"react";export default function b(){const[c,d]=a.useState({hits:[]}),[b,e]=a.useState("react");return a.useEffect(()=>{""!==b&&a();async function a(){const a=await fetch("https://hn.algolia.com/api/v1/search?query="+b),c=await a.json();d(c)}},[b]),<>
+import*as b from"react";export default function c(){const[d,e]=b.useState({hits:[]}),[c,f]=b.useState("react");return b.useEffect(()=>{""!==c&&b();async function b(){const b=await fetch("https://hn.algolia.com/api/v1/search?query="+c),d=await b.json();e(d)}},[c]),<>
 
-            <input value={b}onChange={a=>e(a.target.value)}/>
+            <input value={c}onChange={b=>f(b.target.value)}/>
 
             <ul >
 
-                {c.hits.map(a=><li key={a.objectID}>
+                {d.hits.map(b=><li key={b.objectID}>
 
-                        <a href={a.url}>{a.title}</a>
+                        <a href={b.url}>{b.title}</a>
 
                     </li>)}