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docs(transformer): add documentation for logical-assignment-operators plugin #5012

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Aug 20, 2024
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docs(transformer): add documentation for logical-assignment-operators plugin #5012

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60 changes: 55 additions & 5 deletions crates/oxc_transformer/src/es2021/logical_assignment_operators.rs
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Original file line number Diff line number Diff line change
@@ -1,3 +1,58 @@
//! ES2021: Logical Assignment Operators
//!
//! This plugin transform logical assignment operators `&&=`, `||=`, and `??=` to a series of logical expressions.
//!
//! > This plugin is included in `preset-env`, in ES2021
//!
//! ## Example
//!
//! Input:
//! ```js
//! a ||= b;
//! obj.a.b ||= c;
//!
//! a &&= b;
//! obj.a.b &&= c;
//! ```
//!
//! Output:
//! ```js
//! var _obj$a, _obj$a2;
//!
//! a || (a = b);
//! (_obj$a = obj.a).b || (_obj$a.b = c);
//!
//! a && (a = b);
//! (_obj$a2 = obj.a).b && (_obj$a2.b = c);
//! ```
//!
//! ### With Nullish Coalescing
//!
//! > While using the [nullish-coalescing-operator](https://github.com/oxc-project/oxc/blob/main/crates/oxc_transformer/src/es2020/nullish_coalescing_operator.rs) plugin (included in `preset-env``)
//!
//! Input:
//! ```js
//! a ??= b;
//! obj.a.b ??= c;
//! ```
//!
//! Output:
//! ```js
//! var _a, _obj$a, _obj$a$b;
//!
//! (_a = a) !== null && _a !== void 0 ? _a : (a = b);
//! (_obj$a$b = (_obj$a = obj.a).b) !== null && _obj$a$b !== void 0
//! ? _obj$a$b
//! : (_obj$a.b = c);
//! ```
//! ## Implementation
//!
//! Implementation based on [@babel/plugin-transform-logical-assignment-operators](https://babel.dev/docs/babel-plugin-transform-logical-assignment-operators).
//!
//! ## References:
//! * Babel plugin implementation: <https://github.com/babel/babel/tree/main/packages/babel-plugin-transform-logical-assignment-operators>
//! * Logical Assignment TC39 proposal: <https://github.com/tc39/proposal-logical-assignment>

use std::cell::Cell;

use oxc_allocator::{CloneIn, Vec};
Expand All @@ -9,11 +64,6 @@ use oxc_traverse::TraverseCtx;

use crate::context::Ctx;

/// ES2021: Logical Assignment Operators
///
/// References:
/// * <https://babel.dev/docs/babel-plugin-transform-logical-assignment-operators>
/// * <https://github.com/babel/babel/blob/main/packages/babel-plugin-transform-logical-assignment-operators>
pub struct LogicalAssignmentOperators<'a> {
_ctx: Ctx<'a>,
var_declarations: std::vec::Vec<Vec<'a, VariableDeclarator<'a>>>,
Expand Down