fix(es/minifier): should preserve classes with side effects in static…

… fields

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

@@ -473,10 +473,22 @@ where
         }
 
         match decl {
-            Decl::Class(ClassDecl { ident, .. }) => {
+            Decl::Class(ClassDecl { ident, class, .. }) => {
                 if ident.sym == js_word!("arguments") {
                     return;
                 }
+
+                // Fix https://github.com/swc-project/swc/issues/5588
+                let may_have_side_effect = class.body.iter().any(|m| match m {
+                    ClassMember::ClassProp(p) => p.is_static && p.value.is_some(),
+                    ClassMember::PrivateProp(p) => p.is_static && p.value.is_some(),
+                    ClassMember::StaticBlock(_) => true,
+                    _ => true,
+                });
+                if may_have_side_effect {
+                    return;
+                }
+
                 // If it is not used, drop it.
                 if self
                     .data

crates/swc_ecma_minifier/tests/fixture/issues/5588/config.json

@@ -0,0 +1,4 @@
+{
+    "unused": true,
+    "toplevel": true
+}

crates/swc_ecma_minifier/tests/fixture/issues/5588/input.js

@@ -0,0 +1,12 @@
+"use strict";
+let getFoo;
+let getFoo2
+class Foo {
+    static #foo = 42;
+    static #_ = (getFoo2 = this.#foo)
+    static{
+        getFoo = ()=>this.#foo;
+    }
+}
+expect(getFoo()).toBe(42);
+expect(getFoo2()).toBe(42);

crates/swc_ecma_minifier/tests/fixture/issues/5588/output.js

@@ -0,0 +1,12 @@
+"use strict";
+let getFoo;
+let getFoo2;
+class Foo {
+    static #foo = 42;
+    static #_ = getFoo2 = this.#foo;
+    static{
+        getFoo = ()=>this.#foo;
+    }
+}
+expect(getFoo()).toBe(42);
+expect(getFoo2()).toBe(42);