Migrate to VisitMut (#86347)

This is generally better for performance

Author: mischnic

crates/next-custom-transforms/src/transforms/dynamic.rs

@@ -15,7 +15,7 @@ use swc_core::{
             PropName, PropOrSpread, Stmt, Str, Tpl, UnaryExpr, UnaryOp,
         },
         utils::{private_ident, quote_ident, ExprFactory},
-        visit::{fold_pass, Fold, FoldWith, VisitMut, VisitMutWith},
+        visit::{visit_mut_pass, VisitMut, VisitMutWith},
     },
     quote,
 };
@@ -34,7 +34,7 @@ pub fn next_dynamic(
     filename: Arc<FileName>,
     pages_or_app_dir: Option<PathBuf>,
 ) -> impl Pass {
-    fold_pass(NextDynamicPatcher {
+    visit_mut_pass(NextDynamicPatcher {
         is_development,
         is_server_compiler,
         is_react_server_layer,
@@ -117,33 +117,24 @@ enum TurbopackImport {
     },
 }
 
-impl Fold for NextDynamicPatcher {
-    fn fold_module_items(&mut self, mut items: Vec<ModuleItem>) -> Vec<ModuleItem> {
-        items = items.fold_children_with(self);
+impl VisitMut for NextDynamicPatcher {
+    fn visit_mut_module_items(&mut self, items: &mut Vec<ModuleItem>) {
+        items.visit_mut_children_with(self);
 
-        self.maybe_add_dynamically_imported_specifier(&mut items);
-
-        items
+        self.maybe_add_dynamically_imported_specifier(items);
     }
 
-    fn fold_import_decl(&mut self, decl: ImportDecl) -> ImportDecl {
-        let ImportDecl {
-            ref src,
-            ref specifiers,
-            ..
-        } = decl;
-        if &src.value == "next/dynamic" {
-            for specifier in specifiers {
+    fn visit_mut_import_decl(&mut self, decl: &mut ImportDecl) {
+        if &decl.src.value == "next/dynamic" {
+            for specifier in &decl.specifiers {
                 if let ImportSpecifier::Default(default_specifier) = specifier {
                     self.dynamic_bindings.push(default_specifier.local.to_id());
                 }
             }
         }
-
-        decl
     }
 
-    fn fold_call_expr(&mut self, expr: CallExpr) -> CallExpr {
+    fn visit_mut_call_expr(&mut self, expr: &mut CallExpr) {
         if self.is_next_dynamic_first_arg {
             if let Callee::Import(..) = &expr.callee {
                 match &*expr.args[0].expr {
@@ -157,9 +148,12 @@ impl Fold for NextDynamicPatcher {
                     _ => {}
                 }
             }
-            return expr.fold_children_with(self);
+            expr.visit_mut_children_with(self);
+            return;
         }
-        let mut expr = expr.fold_children_with(self);
+
+        expr.visit_mut_children_with(self);
+
         if let Callee::Expr(i) = &expr.callee {
             if let Expr::Ident(identifier) = &**i {
                 if self.dynamic_bindings.contains(&identifier.to_id()) {
@@ -172,7 +166,7 @@ impl Fold for NextDynamicPatcher {
                                 )
                                 .emit()
                         });
-                        return expr;
+                        return;
                     } else if expr.args.len() > 2 {
                         HANDLER.with(|handler| {
                             handler
@@ -182,7 +176,7 @@ impl Fold for NextDynamicPatcher {
                                 )
                                 .emit()
                         });
-                        return expr;
+                        return;
                     }
                     if expr.args.len() == 2 {
                         match &*expr.args[1].expr {
@@ -196,19 +190,19 @@ impl Fold for NextDynamicPatcher {
                               )
                               .emit();
                       });
-                                return expr;
+                                return;
                             }
                         }
                     }
 
                     self.is_next_dynamic_first_arg = true;
-                    expr.args[0].expr = expr.args[0].expr.clone().fold_with(self);
+                    expr.args[0].expr.visit_mut_with(self);
                     self.is_next_dynamic_first_arg = false;
 
                     let Some((dynamically_imported_specifier, dynamically_imported_specifier_span)) =
                         self.dynamically_imported_specifier.take()
                     else {
-                        return expr;
+                        return;
                     };
 
                     let project_dir = match self.pages_or_app_dir.as_deref() {
@@ -419,7 +413,6 @@ impl Fold for NextDynamicPatcher {
                 }
             }
         }
-        expr
     }
 }
 

crates/next-custom-transforms/src/transforms/named_import_transform.rs

@@ -5,7 +5,7 @@ use swc_core::{
     common::DUMMY_SP,
     ecma::{
         ast::*,
-        visit::{fold_pass, Fold},
+        visit::{visit_mut_pass, VisitMut},
     },
 };
 
@@ -14,8 +14,8 @@ pub struct Config {
     pub packages: Vec<String>,
 }
 
-pub fn named_import_transform(config: Config) -> impl Pass {
-    fold_pass(NamedImportTransform {
+pub fn named_import_transform(config: Config) -> impl Pass + VisitMut {
+    visit_mut_pass(NamedImportTransform {
         packages: config.packages,
     })
 }
@@ -25,9 +25,8 @@ struct NamedImportTransform {
     packages: Vec<String>,
 }
 
-/// TODO: Implement this as a [Pass] instead of a full visitor ([Fold])
-impl Fold for NamedImportTransform {
-    fn fold_import_decl(&mut self, decl: ImportDecl) -> ImportDecl {
+impl VisitMut for NamedImportTransform {
+    fn visit_mut_import_decl(&mut self, decl: &mut ImportDecl) {
         // Match named imports and check if it's included in the packages
         let src_value = &decl.src.value;
 
@@ -75,18 +74,12 @@ impl Fold for NamedImportTransform {
                     src_value.to_string_lossy()
                 );
 
-                // Create a new import declaration, keep everything the same except the source
-                let mut new_decl = decl.clone();
-                *new_decl.src = Str {
+                *decl.src = Str {
                     span: DUMMY_SP,
                     value: new_src.into(),
                     raw: None,
                 };
-
-                return new_decl;
             }
         }
-
-        decl
     }
 }