fix(es/decorator): Add support for private access expressions in legacy decorators (#9535)

**Related issue:**

- Closes #9429

Author: magic-akari

.changeset/nasty-ligers-reflect.md

@@ -0,0 +1,6 @@
+---
+swc_ecma_transforms_proposal: patch
+swc_core: patch
+---
+
+fix(es/decorator): Add support for private access expressions in legacy decorators

crates/swc/tests/fixture/issues-9xxx/9429/input/.swcrc

@@ -0,0 +1,20 @@
+{
+  "jsc": {
+    "parser": {
+      "syntax": "typescript",
+      "tsx": true,
+      "decorators": true
+    },
+    "target": "es2022",
+    "loose": false,
+    "minify": {
+      "compress": false,
+      "mangle": false
+    }
+  },
+  "module": {
+    "type": "es6"
+  },
+  "minify": false,
+  "isModule": true
+}

crates/swc/tests/fixture/issues-9xxx/9429/input/index.ts

@@ -0,0 +1,25 @@
+class Foo {
+  static #loggedMethod<Args extends unknown[], Ret>(
+    _prototype: typeof Foo.prototype,
+    _propertyKey: string,
+    descriptor: TypedPropertyDescriptor<(this: Foo, ...args: Args) => Promise<Ret>>,
+  ) {
+    const method = descriptor.value!;
+    descriptor.value = function (...args) {
+      try {
+        console.log("before");
+        return method.apply(this, args);
+      } finally {
+        console.log("after");
+      }
+    };
+  }
+
+  @(Foo.#loggedMethod)
+  public greet(): any {
+    console.log("hi");
+  }
+}
+
+const foo = new Foo();
+foo.greet();

crates/swc/tests/fixture/issues-9xxx/9429/input/test.ts

@@ -0,0 +1,24 @@
+class Foo {
+    static {
+        class Bar {
+            static #x() {}
+
+            @Bar.#x
+            foo() {}
+        }
+    }
+
+    static #y() {}
+
+    @Foo.#y
+    public foo() {}
+
+    static {
+        class Bar {
+            static #x() {}
+
+            @Bar.#x
+            foo() {}
+        }
+    }
+}

crates/swc/tests/fixture/issues-9xxx/9429/output/index.ts

@@ -0,0 +1,24 @@
+var _ts_decorate = require("@swc/helpers/_/_ts_decorate");
+class Foo {
+    static #loggedMethod(_prototype, _propertyKey, descriptor) {
+        const method = descriptor.value;
+        descriptor.value = function(...args) {
+            try {
+                console.log("before");
+                return method.apply(this, args);
+            } finally{
+                console.log("after");
+            }
+        };
+    }
+    greet() {
+        console.log("hi");
+    }
+    static{
+        _ts_decorate._([
+            Foo.#loggedMethod
+        ], Foo.prototype, "greet", null);
+    }
+}
+const foo = new Foo();
+foo.greet();

crates/swc/tests/fixture/issues-9xxx/9429/output/test.ts

@@ -0,0 +1,32 @@
+var _ts_decorate = require("@swc/helpers/_/_ts_decorate");
+class Foo {
+    static{
+        class Bar {
+            static #x() {}
+            foo() {}
+            static{
+                _ts_decorate._([
+                    Bar.#x
+                ], Bar.prototype, "foo", null);
+            }
+        }
+    }
+    static #y() {}
+    foo() {}
+    static{
+        class Bar {
+            static #x() {}
+            foo() {}
+            static{
+                _ts_decorate._([
+                    Bar.#x
+                ], Bar.prototype, "foo", null);
+            }
+        }
+    }
+    static{
+        _ts_decorate._([
+            Foo.#y
+        ], Foo.prototype, "foo", null);
+    }
+}

crates/swc_ecma_transforms_proposal/src/decorators/legacy/mod.rs

@@ -26,6 +26,7 @@ pub(super) fn new(metadata: bool) -> TscDecorator {
         enums: Default::default(),
         vars: Default::default(),
         appended_exprs: Default::default(),
+        appended_private_access_exprs: Default::default(),
         prepended_exprs: Default::default(),
         class_name: Default::default(),
 
@@ -41,6 +42,7 @@ pub(super) struct TscDecorator {
     /// Used for computed keys, and this variables are not initialized.
     vars: Vec<VarDeclarator>,
     appended_exprs: Vec<Box<Expr>>,
+    appended_private_access_exprs: Vec<Box<Expr>>,
     prepended_exprs: Vec<Box<Expr>>,
 
     class_name: Option<Ident>,
@@ -155,6 +157,17 @@ impl TscDecorator {
         prop_name_to_expr_value(k.clone())
     }
 
+    fn has_private_access(mut expr: &Expr) -> bool {
+        while let Some(MemberExpr { obj, prop, .. }) = expr.as_member() {
+            if prop.is_private_name() {
+                return true;
+            }
+            expr = obj;
+        }
+
+        false
+    }
+
     /// Creates `__decorate` calls.
     fn add_decorate_call(
         &mut self,
@@ -163,10 +176,17 @@ impl TscDecorator {
         key: ExprOrSpread,
         mut desc: ExprOrSpread,
     ) {
+        let mut has_private_access = false;
         let decorators = ArrayLit {
             span: DUMMY_SP,
             elems: decorators
                 .into_iter()
+                .inspect(|e| {
+                    if has_private_access {
+                        return;
+                    }
+                    has_private_access = Self::has_private_access(e);
+                })
                 .map(|mut v| {
                     remove_span(&mut v);
 
@@ -180,15 +200,18 @@ impl TscDecorator {
         remove_span(&mut target.expr);
         remove_span(&mut desc.expr);
 
-        self.appended_exprs.push(
-            CallExpr {
-                span: DUMMY_SP,
-                callee: helper!(ts, ts_decorate),
-                args: vec![decorators, target, key, desc],
-                ..Default::default()
-            }
-            .into(),
-        );
+        let expr = CallExpr {
+            callee: helper!(ts, ts_decorate),
+            args: vec![decorators, target, key, desc],
+            ..Default::default()
+        }
+        .into();
+
+        if has_private_access {
+            self.appended_private_access_exprs.push(expr);
+        } else {
+            self.appended_exprs.push(expr);
+        }
     }
 }
 
@@ -235,6 +258,8 @@ impl Visit for TscDecorator {
 
 impl VisitMut for TscDecorator {
     fn visit_mut_class(&mut self, n: &mut Class) {
+        let appended_private = self.appended_private_access_exprs.take();
+
         n.visit_mut_with(&mut ParamMetadata);
 
         if self.metadata {
@@ -245,6 +270,32 @@ impl VisitMut for TscDecorator {
 
         n.visit_mut_children_with(self);
 
+        let appended_private =
+            mem::replace(&mut self.appended_private_access_exprs, appended_private);
+
+        if !appended_private.is_empty() {
+            let expr = if appended_private.len() == 1 {
+                *appended_private.into_iter().next().unwrap()
+            } else {
+                SeqExpr {
+                    exprs: appended_private,
+                    ..Default::default()
+                }
+                .into()
+            };
+
+            n.body.push(
+                StaticBlock {
+                    body: BlockStmt {
+                        stmts: vec![expr.into_stmt()],
+                        ..Default::default()
+                    },
+                    ..Default::default()
+                }
+                .into(),
+            )
+        }
+
         if let Some(class_name) = self.class_name.clone() {
             if !n.decorators.is_empty() {
                 let decorators = ArrayLit {