From bf066e18460a03ecf47e7a6a60ca6741bcab7de0 Mon Sep 17 00:00:00 2001
From: YunfeiHe <i.heyunfei@gmail.com>
Date: Sat, 19 Nov 2022 14:57:09 +0800
Subject: [PATCH] fix(es/minifier): should preserve classes with side effects
 in static fields

---
 .../src/compress/optimize/unused.rs                | 14 +++++++++++++-
 .../tests/fixture/issues/5588/config.json          |  4 ++++
 .../tests/fixture/issues/5588/input.js             | 12 ++++++++++++
 .../tests/fixture/issues/5588/output.js            | 12 ++++++++++++
 4 files changed, 41 insertions(+), 1 deletion(-)
 create mode 100644 crates/swc_ecma_minifier/tests/fixture/issues/5588/config.json
 create mode 100644 crates/swc_ecma_minifier/tests/fixture/issues/5588/input.js
 create mode 100644 crates/swc_ecma_minifier/tests/fixture/issues/5588/output.js

diff --git a/crates/swc_ecma_minifier/src/compress/optimize/unused.rs b/crates/swc_ecma_minifier/src/compress/optimize/unused.rs
index 1aa13c5dcd9f..b5433a24eaac 100644
--- a/crates/swc_ecma_minifier/src/compress/optimize/unused.rs
+++ b/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
diff --git a/crates/swc_ecma_minifier/tests/fixture/issues/5588/config.json b/crates/swc_ecma_minifier/tests/fixture/issues/5588/config.json
new file mode 100644
index 000000000000..b987119e94fb
--- /dev/null
+++ b/crates/swc_ecma_minifier/tests/fixture/issues/5588/config.json
@@ -0,0 +1,4 @@
+{
+    "unused": true,
+    "toplevel": true
+}
\ No newline at end of file
diff --git a/crates/swc_ecma_minifier/tests/fixture/issues/5588/input.js b/crates/swc_ecma_minifier/tests/fixture/issues/5588/input.js
new file mode 100644
index 000000000000..8581920fa47e
--- /dev/null
+++ b/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);
\ No newline at end of file
diff --git a/crates/swc_ecma_minifier/tests/fixture/issues/5588/output.js b/crates/swc_ecma_minifier/tests/fixture/issues/5588/output.js
new file mode 100644
index 000000000000..f70de3b7c4fe
--- /dev/null
+++ b/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);