Detect TSC polyfills to avoid marking them as CJS

packages/transformers/js/core/src/collect.rs

@@ -767,6 +767,25 @@ impl Visit for Collect {
           self.used_imports.insert(id!(ident));
         }
       }
+      Expr::Bin(bin_expr) => {
+        // Some TSC polyfills use a pattern like below.
+        // We want to avoid marking these modules as CJS
+        // e.g. var _polyfill = (this && this.polyfill) || function () {}
+        if matches!(*bin_expr.left, Expr::This(..)) {
+          match &*bin_expr.right {
+            Expr::Member(member_expr) => {
+              if matches!(*member_expr.obj, Expr::This(..))
+                && matches!(member_expr.prop, MemberProp::Ident(..))
+              {
+                return;
+              }
+            }
+            _ => {}
+          }
+        }
+
+        node.visit_children_with(self);
+      }
       _ => {
         node.visit_children_with(self);
       }

packages/transformers/js/core/src/hoist.rs

@@ -1424,6 +1424,32 @@ mod tests {
     assert!(collect.should_wrap);
   }
 
+  #[test]
+  fn collect_has_cjs_exports() {
+    let (collect, _code, _hoist) = parse(
+      r#"
+      module.exports = {};
+    "#,
+    );
+    assert!(collect.has_cjs_exports);
+
+    let (collect, _code, _hoist) = parse(
+      r#"
+      this.someExport = 'true';
+    "#,
+    );
+    assert!(collect.has_cjs_exports);
+
+    // Some TSC polyfills use a pattern like below.
+    // We want to avoid marking these modules as CJS
+    let (collect, _code, _hoist) = parse(
+      r#"
+      var __classPrivateFieldSet = (this && this.__classPrivateFieldSet) || function () {}
+    "#,
+    );
+    assert!(!collect.has_cjs_exports);
+  }
+
   #[test]
   fn collect_should_wrap() {
     let (collect, _code, _hoist) = parse(