From 79ca6feca9745d3a32696d70cc06bd8c4fbb93ba Mon Sep 17 00:00:00 2001
From: Boshen <boshenc@gmail.com>
Date: Wed, 10 Apr 2024 11:06:49 +0800
Subject: [PATCH] feat(transformer): add transform callback methods (#2929)

For milestone 1, I think it's safe to just layout all the
transformations manually.


In TypeScript, the transformers are collected dynamically and ran on
each ast node; this achieves a single AST pass.
https://github.com/microsoft/TypeScript/blob/main/src/compiler/transformer.ts#L129-L145

To maximize performance and reduce confusion, I think it's safe to
layout all the transformations manually for milestone 1.

The next PR will add transformation context to all presets so we can
start adding "context".
---
 crates/oxc_transformer/src/decorators/mod.rs |  7 ++++
 crates/oxc_transformer/src/lib.rs            | 36 +++++++++++++++-----
 crates/oxc_transformer/src/react/mod.rs      | 18 ++++++++++
 crates/oxc_transformer/src/typescript/mod.rs |  7 ++++
 4 files changed, 60 insertions(+), 8 deletions(-)

diff --git a/crates/oxc_transformer/src/decorators/mod.rs b/crates/oxc_transformer/src/decorators/mod.rs
index 8fbe511f7..05ac442d7 100644
--- a/crates/oxc_transformer/src/decorators/mod.rs
+++ b/crates/oxc_transformer/src/decorators/mod.rs
@@ -1,5 +1,7 @@
 use serde::Deserialize;
 
+use oxc_ast::ast::*;
+
 /// Only `"2023-11"` will be implemented because Babel 8 will only support "2023-11" and "legacy".
 #[derive(Debug, Default, Clone, Deserialize)]
 #[serde(rename_all = "camelCase")]
@@ -17,3 +19,8 @@ impl Decorators {
         Self { options }
     }
 }
+
+// Transformers
+impl Decorators {
+    pub fn transform_statement(&mut self, _stmt: &mut Statement<'_>) {}
+}
diff --git a/crates/oxc_transformer/src/lib.rs b/crates/oxc_transformer/src/lib.rs
index 5748c6840..9eb61af4e 100644
--- a/crates/oxc_transformer/src/lib.rs
+++ b/crates/oxc_transformer/src/lib.rs
@@ -1,3 +1,5 @@
+#![allow(clippy::wildcard_imports)]
+
 //! Transformer / Transpiler
 //!
 //! References:
@@ -13,7 +15,10 @@ mod react;
 mod typescript;
 
 use oxc_allocator::Allocator;
-use oxc_ast::ast::Program;
+use oxc_ast::{
+    ast::*,
+    visit::{walk_mut, VisitMut},
+};
 use oxc_diagnostics::Error;
 use oxc_semantic::Semantic;
 use oxc_span::SourceType;
@@ -54,9 +59,10 @@ pub struct Transformer<'a> {
     semantic: Semantic<'a>,
     options: TransformOptions,
 
-    decorators: Decorators,
-    typescript: TypeScript,
-    react: React,
+    // NOTE: all callbacks must run in order.
+    x0_typescript: TypeScript,
+    x1_react: React,
+    x2_decorators: Decorators,
 }
 
 impl<'a> Transformer<'a> {
@@ -71,16 +77,30 @@ impl<'a> Transformer<'a> {
             source_type,
             semantic,
             options,
-            decorators: Decorators::default(),
-            typescript: TypeScript::default(),
-            react: React::default(),
+            x0_typescript: TypeScript::default(),
+            x1_react: React::default(),
+            x2_decorators: Decorators::default(),
         }
     }
 
     /// # Errors
     ///
     /// Returns `Vec<Error>` if any errors were collected during the transformation.
-    pub fn build(self, _program: &mut Program<'a>) -> Result<(), Vec<Error>> {
+    pub fn build(mut self, program: &mut Program<'a>) -> Result<(), Vec<Error>> {
+        self.visit_program(program);
         Ok(())
     }
 }
+
+impl<'a> VisitMut<'a> for Transformer<'a> {
+    fn visit_statement(&mut self, stmt: &mut Statement<'a>) {
+        self.x0_typescript.transform_statement(stmt);
+        self.x2_decorators.transform_statement(stmt);
+        walk_mut::walk_statement_mut(self, stmt);
+    }
+
+    fn visit_expression(&mut self, expr: &mut Expression<'a>) {
+        self.x1_react.transform_expression(expr);
+        walk_mut::walk_expression_mut(self, expr);
+    }
+}
diff --git a/crates/oxc_transformer/src/react/mod.rs b/crates/oxc_transformer/src/react/mod.rs
index 6a0cae35c..7bd07cd0e 100644
--- a/crates/oxc_transformer/src/react/mod.rs
+++ b/crates/oxc_transformer/src/react/mod.rs
@@ -4,6 +4,8 @@ mod jsx_self;
 mod jsx_source;
 mod options;
 
+use oxc_ast::ast::*;
+
 pub use self::{
     display_name::{ReactDisplayName, ReactDisplayNameOptions},
     jsx::ReactJsx,
@@ -28,6 +30,7 @@ pub struct React {
     display_name: ReactDisplayName,
 }
 
+// Constructors
 impl React {
     pub fn new(&mut self, options: ReactOptions) -> &mut Self {
         self.jsx = ReactJsx::new(options);
@@ -49,3 +52,18 @@ impl React {
         self
     }
 }
+
+// Transformers
+impl React {
+    pub fn transform_expression(&mut self, expr: &mut Expression<'_>) {
+        match expr {
+            Expression::JSXElement(_e) => {
+                // *expr = unimplemented!();
+            }
+            Expression::JSXFragment(_e) => {
+                // *expr = unimplemented!();
+            }
+            _ => {}
+        }
+    }
+}
diff --git a/crates/oxc_transformer/src/typescript/mod.rs b/crates/oxc_transformer/src/typescript/mod.rs
index 197e79a80..0fb7d1683 100644
--- a/crates/oxc_transformer/src/typescript/mod.rs
+++ b/crates/oxc_transformer/src/typescript/mod.rs
@@ -1,5 +1,7 @@
 use serde::Deserialize;
 
+use oxc_ast::ast::*;
+
 #[derive(Debug, Default, Clone, Deserialize)]
 #[serde(rename_all = "camelCase")]
 pub struct TypeScriptOptions;
@@ -36,3 +38,8 @@ impl TypeScript {
         Self { options }
     }
 }
+
+// Transformers
+impl TypeScript {
+    pub fn transform_statement(&mut self, _stmt: &mut Statement<'_>) {}
+}