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graphite-app merged 1 commit into from
Aug 25, 2024
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docs(transformer): add documentation for arrow-functions plugin #5186

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102 changes: 61 additions & 41 deletions crates/oxc_transformer/src/es2015/arrow_functions.rs
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Original file line number Diff line number Diff line change
@@ -1,3 +1,64 @@
//! ES2015 Arrow Functions
//!
//! This plugin transforms arrow functions (`() => {}`) to function expressions (`function () {}`).
//!
//! > This plugin is included in `preset-env`, in ES2015
//!
//! ## Example
//!
//! Input:
//! ```js
//! var a = () => {};
//! var a = b => b;
//!
//! const double = [1, 2, 3].map(num => num * 2);
//! console.log(double); // [2,4,6]
//!
//! var bob = {
//! _name: "Bob",
//! _friends: ["Sally", "Tom"],
//! printFriends() {
//! this._friends.forEach(f => console.log(this._name + " knows " + f));
//! },
//! };
//! console.log(bob.printFriends());
//! ```
//!
//! Output:
//! ```js
//! var a = function() {};
//! var a = function(b) {
//! return b;
//! };
//!
//! const double = [1, 2, 3].map(function(num) {
//! return num * 2;
//! });
//! console.log(double); // [2,4,6]
//!
//! var bob = {
//! _name: "Bob",
//! _friends: ["Sally", "Tom"],
//! printFriends() {
//! var _this = this;
//!
//! this._friends.forEach(function(f) {
//! return console.log(_this._name + " knows " + f);
//! });
//! },
//! };
//! console.log(bob.printFriends());
//! ```
//!
//! ## Implementation
//!
//! Implementation based on [@babel/plugin-transform-exponentiation-operator](https://babel.dev/docs/babel-plugin-transform-arrow-functions).
//!
//! ## References:
//!
//! * Babel plugin implementation: <https://github.com/babel/babel/blob/main/packages/babel-plugin-transform-arrow-functions>
//! * Arrow function specification: <https://tc39.es/ecma262/#sec-arrow-function-definitions>

use std::cell::Cell;

use oxc_allocator::Vec;
Expand All @@ -19,47 +80,6 @@ pub struct ArrowFunctionsOptions {
pub spec: bool,
}

/// [plugin-transform-arrow-functions](https://babel.dev/docs/babel-plugin-transform-arrow-functions)
///
/// This plugin transforms arrow functions to function expressions.
///
/// This plugin is included in `preset-env`
///
/// References:
///
/// * <https://babeljs.io/docs/babel-plugin-transform-arrow-functions>
/// * <https://github.com/babel/babel/tree/main/packages/babel-plugin-transform-arrow-functions>
//
// TODO: The `spec` option is not currently supported. Add support for it.
//
// TODO: We create `var _this = this;` in parent block, whereas we should create it in
// parent vars block like Babel:
// ```js
// // Input
// function foo() {
// { let f = () => this; }
// { let f2 = () => this; }
// }
//
// // Babel output
// function foo() {
// var _this = this;
// { let f = function () { return _this; } }
// { let f2 = function () { return _this; } }
// }
//
// // Our output
// function foo() {
// {
// var _this = this;
// let f = function () { return _this; }
// }
// {
// var _this2 = this;
// let f2 = function () { return _this2; }
// }
// }
// ```
pub struct ArrowFunctions<'a> {
ctx: Ctx<'a>,
_options: ArrowFunctionsOptions,
Expand Down