feat(transformer): support optional-catch-binding plugin (#4885)

part of #4754

The implementation copy from the original implementation which removed in https://github.com/oxc-project/oxc/pull/2865.

crates/oxc_transformer/src/es2019/mod.rs

@@ -0,0 +1,35 @@
+mod optional_catch_binding;
+mod options;
+
+pub use optional_catch_binding::OptionalCatchBinding;
+pub use options::ES2019Options;
+use oxc_ast::ast::*;
+use oxc_traverse::TraverseCtx;
+use std::rc::Rc;
+
+use crate::context::Ctx;
+
+#[allow(dead_code)]
+pub struct ES2019<'a> {
+    ctx: Ctx<'a>,
+    options: ES2019Options,
+
+    // Plugins
+    optional_catch_binding: OptionalCatchBinding<'a>,
+}
+
+impl<'a> ES2019<'a> {
+    pub fn new(options: ES2019Options, ctx: Ctx<'a>) -> Self {
+        Self { optional_catch_binding: OptionalCatchBinding::new(Rc::clone(&ctx)), ctx, options }
+    }
+
+    pub fn transform_catch_clause(
+        &mut self,
+        clause: &mut CatchClause<'a>,
+        ctx: &mut TraverseCtx<'a>,
+    ) {
+        if self.options.optional_catch_binding {
+            self.optional_catch_binding.transform_catch_clause(clause, ctx);
+        }
+    }
+}

crates/oxc_transformer/src/es2019/optional_catch_binding.rs

@@ -0,0 +1,52 @@
+use std::cell::Cell;
+
+use oxc_ast::ast::*;
+use oxc_semantic::SymbolFlags;
+use oxc_span::SPAN;
+use oxc_traverse::TraverseCtx;
+
+use crate::context::Ctx;
+
+/// ES2019: Optional Catch Binding
+///
+/// References:
+/// * <https://babel.dev/docs/babel-plugin-transform-optional-catch-binding>
+/// * <https://github.com/babel/babel/tree/main/packages/babel-plugin-transform-optional-catch-binding>
+pub struct OptionalCatchBinding<'a> {
+    _ctx: Ctx<'a>,
+}
+
+impl<'a> OptionalCatchBinding<'a> {
+    pub fn new(ctx: Ctx<'a>) -> Self {
+        Self { _ctx: ctx }
+    }
+
+    /// If CatchClause has no param, add a parameter called `unused`.
+    ///
+    /// ```ts
+    /// try {}
+    /// catch {}
+    /// ```
+    /// too
+    /// ```ts
+    /// try {}
+    /// catch (_unused) {}
+    /// ```
+    #[allow(clippy::unused_self)]
+    pub fn transform_catch_clause(&self, clause: &mut CatchClause<'a>, ctx: &mut TraverseCtx<'a>) {
+        if clause.param.is_some() {
+            return;
+        }
+        let symbol_id =
+            ctx.generate_uid("unused", ctx.scoping.current_scope_id(), SymbolFlags::CatchVariable);
+        let name = ctx.ast.atom(ctx.symbols().get_name(symbol_id));
+        let binding_identifier =
+            BindingIdentifier { span: SPAN, symbol_id: Cell::new(Some(symbol_id)), name };
+        let binding_pattern_kind =
+            ctx.ast.binding_pattern_kind_from_binding_identifier(binding_identifier);
+        let binding_pattern =
+            ctx.ast.binding_pattern(binding_pattern_kind, None::<TSTypeAnnotation<'a>>, false);
+        let param = ctx.ast.catch_parameter(SPAN, binding_pattern);
+        clause.param = Some(param);
+    }
+}

crates/oxc_transformer/src/es2019/options.rs

@@ -0,0 +1,16 @@
+use serde::Deserialize;
+
+#[derive(Debug, Default, Clone, Deserialize)]
+#[serde(default, rename_all = "camelCase", deny_unknown_fields)]
+pub struct ES2019Options {
+    #[serde(skip)]
+    pub optional_catch_binding: bool,
+}
+
+impl ES2019Options {
+    #[must_use]
+    pub fn with_optional_catch_binding(mut self, enable: bool) -> Self {
+        self.optional_catch_binding = enable;
+        self
+    }
+}

crates/oxc_transformer/src/lib.rs

@@ -16,6 +16,7 @@ mod options;
 mod env;
 mod es2015;
 mod es2016;
+mod es2019;
 mod es2020;
 mod react;
 mod typescript;
@@ -28,6 +29,7 @@ mod helpers {
 use std::{path::Path, rc::Rc};
 
 use es2016::ES2016;
+use es2019::ES2019;
 use es2020::ES2020;
 use oxc_allocator::{Allocator, Vec};
 use oxc_ast::{ast::*, AstBuilder, Trivias};
@@ -63,6 +65,7 @@ pub struct Transformer<'a> {
     x0_typescript: TypeScript<'a>,
     x1_react: React<'a>,
     x2_es2020: ES2020<'a>,
+    x2_es2019: ES2019<'a>,
     x2_es2016: ES2016<'a>,
     x3_es2015: ES2015<'a>,
 }
@@ -88,8 +91,9 @@ impl<'a> Transformer<'a> {
             ctx: Rc::clone(&ctx),
             x0_typescript: TypeScript::new(options.typescript, Rc::clone(&ctx)),
             x1_react: React::new(options.react, Rc::clone(&ctx)),
-            x2_es2016: ES2016::new(options.es2016, Rc::clone(&ctx)),
             x2_es2020: ES2020::new(options.es2020, Rc::clone(&ctx)),
+            x2_es2019: ES2019::new(options.es2019, Rc::clone(&ctx)),
+            x2_es2016: ES2016::new(options.es2016, Rc::clone(&ctx)),
             x3_es2015: ES2015::new(options.es2015, ctx),
         }
     }
@@ -317,6 +321,10 @@ impl<'a> Traverse<'a> for Transformer<'a> {
         self.x0_typescript.transform_for_in_statement(stmt, ctx);
     }
 
+    fn enter_catch_clause(&mut self, clause: &mut CatchClause<'a>, ctx: &mut TraverseCtx<'a>) {
+        self.x2_es2019.transform_catch_clause(clause, ctx);
+    }
+
     fn enter_ts_export_assignment(
         &mut self,
         export_assignment: &mut TSExportAssignment<'a>,

crates/oxc_transformer/src/options/transformer.rs

@@ -8,6 +8,7 @@ use crate::{
     env::{can_enable_plugin, EnvOptions, Versions},
     es2015::{ArrowFunctionsOptions, ES2015Options},
     es2016::ES2016Options,
+    es2019::ES2019Options,
     es2020::ES2020Options,
     options::babel::BabelOptions,
     react::ReactOptions,
@@ -39,6 +40,8 @@ pub struct TransformOptions {
 
     pub es2016: ES2016Options,
 
+    pub es2019: ES2019Options,
+
     pub es2020: ES2020Options,
 }
 
@@ -115,6 +118,11 @@ impl TransformOptions {
             enable_plugin(plugin_name, options, &env_options, &targets).is_some()
         });
 
+        let es2019 = ES2019Options::default().with_optional_catch_binding({
+            let plugin_name = "transform-optional-catch-binding";
+            enable_plugin(plugin_name, options, &env_options, &targets).is_some()
+        });
+
         let es2020 = ES2020Options::default().with_nullish_coalescing_operator({
             let plugin_name = "transform-nullish-coalescing-operator";
             enable_plugin(plugin_name, options, &env_options, &targets).is_some()
@@ -152,6 +160,7 @@ impl TransformOptions {
             react,
             es2015,
             es2016,
+            es2019,
             es2020,
         })
     }

tasks/transform_conformance/babel.snap.md

@@ -1,8 +1,9 @@
 commit: 12619ffe
 
-Passed: 458/943
+Passed: 462/947
 
 # All Passed:
+* babel-plugin-transform-optional-catch-binding
 * babel-preset-react
 * babel-plugin-transform-react-display-name
 * babel-plugin-transform-react-jsx-self

tasks/transform_conformance/babel_exec.snap.md

@@ -1,9 +1,10 @@
 commit: 12619ffe
 
-Passed: 12/18
+Passed: 13/19
 
 # All Passed:
 * babel-plugin-transform-nullish-coalescing-operator
+* babel-plugin-transform-optional-catch-binding
 * babel-plugin-transform-exponentiation-operator
 * babel-plugin-transform-arrow-functions
 

tasks/transform_conformance/oxc.snap.md

@@ -1,8 +1,9 @@
 commit: 12619ffe
 
-Passed: 5/8
+Passed: 6/9
 
 # All Passed:
+* babel-plugin-transform-optional-catch-binding
 * babel-plugin-transform-react-jsx
 
 

tasks/transform_conformance/src/constants.rs

@@ -20,7 +20,7 @@ pub(crate) const PLUGINS: &[&str] = &[
     // // [Syntax] "babel-plugin-transform-syntax-dynamic-import",
     // // [Syntax] "babel-plugin-transform-syntax-import-meta",
     // // ES2019
-    // "babel-plugin-transform-optional-catch-binding",
+    "babel-plugin-transform-optional-catch-binding",
     // "babel-plugin-transform-json-strings",
     // // ES2018
     // "babel-plugin-transform-async-generator-functions",