perf(es/compat): Merge optional_catch_binding

crates/swc_ecma_compat_es2019/Cargo.toml

@@ -18,6 +18,7 @@ unexpected_cfgs = { level = "warn", check-cfg = ['cfg(swc_ast_unknown)'] }
 [dependencies]
 swc_common               = { version = "17.0.1", path = "../swc_common" }
 swc_ecma_ast             = { version = "18.0.0", path = "../swc_ecma_ast" }
+swc_ecma_transformer = { version = "0.1.0", path = "../swc_ecma_transformer" }
 swc_ecma_transforms_base = { version = "30.0.0", path = "../swc_ecma_transforms_base" }
 swc_ecma_utils           = { version = "24.0.0", path = "../swc_ecma_utils" }
 swc_ecma_visit           = { version = "18.0.1", path = "../swc_ecma_visit" }

crates/swc_ecma_compat_es2019/src/optional_catch_binding.rs

@@ -3,24 +3,10 @@ use swc_ecma_utils::private_ident;
 use swc_ecma_visit::{noop_visit_mut_type, visit_mut_pass, VisitMut, VisitMutWith};
 use swc_trace_macro::swc_trace;
 
-struct OptionalCatchBinding;
-
 pub fn optional_catch_binding() -> impl Pass {
-    visit_mut_pass(OptionalCatchBinding)
-}
-
-#[swc_trace]
-impl VisitMut for OptionalCatchBinding {
-    noop_visit_mut_type!(fail);
-
-    fn visit_mut_catch_clause(&mut self, cc: &mut CatchClause) {
-        cc.visit_mut_children_with(self);
-
-        if cc.param.is_some() {
-            return;
-        }
-        cc.param = Some(private_ident!("e").into());
-    }
+    let mut options = swc_ecma_transformer::Options::default();
+    options.env.es2019.optional_catch_binding = true;
+    options.into_pass()
 }
 
 #[cfg(test)]

crates/swc_ecma_preset_env/src/lib.rs

@@ -185,7 +185,9 @@ where
     );
 
     // ES2019
-    let pass = add!(pass, OptionalCatchBinding, es2019::optional_catch_binding());
+    if !caniuse(Feature::OptionalCatchBinding) {
+        options.env.es2019.optional_catch_binding = true;
+    }
 
     // ES2018
     if !caniuse(Feature::ObjectRestSpread) {

crates/swc_ecma_transformer/src/es2019/mod.rs

@@ -1,17 +1,19 @@
 use swc_ecma_hooks::VisitMutHook;
 
-use crate::TraverseCtx;
+use crate::{hook_utils::OptionalHook, TraverseCtx};
+
+mod optional_catch_binding;
 
 #[derive(Debug, Default)]
 #[non_exhaustive]
-pub struct Es2019Options {}
-
-pub fn hook(options: Es2019Options) -> impl VisitMutHook<TraverseCtx> {
-    Es2019Pass { options }
+pub struct Es2019Options {
+    pub optional_catch_binding: bool,
 }
 
-struct Es2019Pass {
-    options: Es2019Options,
+pub(crate) fn hook(options: Es2019Options) -> impl VisitMutHook<TraverseCtx> {
+    OptionalHook(if options.optional_catch_binding {
+        Some(self::optional_catch_binding::hook())
+    } else {
+        None
+    })
 }
-
-impl VisitMutHook<TraverseCtx> for Es2019Pass {}

crates/swc_ecma_transformer/src/es2019/optional_catch_binding.rs

@@ -0,0 +1,21 @@
+use swc_ecma_ast::*;
+use swc_ecma_hooks::VisitMutHook;
+use swc_ecma_utils::private_ident;
+
+use crate::TraverseCtx;
+
+pub fn hook() -> impl VisitMutHook<TraverseCtx> {
+    OptionalCatchBindingPass {}
+}
+
+struct OptionalCatchBindingPass {}
+
+impl VisitMutHook<TraverseCtx> for OptionalCatchBindingPass {
+    fn enter_catch_clause(&mut self, node: &mut CatchClause, _: &mut TraverseCtx) {
+        if node.param.is_none() {
+            // TODO: Do not use private_ident! here.
+            // All private identifiers should be tracked using TraverseCtx.
+            node.param = Some(Pat::Ident(private_ident!("unused")));
+        }
+    }
+}

crates/swc_ecma_transformer/src/hook_utils.rs

@@ -50,6 +50,8 @@ where
     optional_method!(enter_script, exit_script, Script);
 
     optional_method!(enter_program, exit_program, Program);
+
+    optional_method!(enter_catch_clause, exit_catch_clause, CatchClause);
 }
 
 pub(crate) struct NoopHook;