feat(transformer): support logical-assignment-operators plugin (#4890)

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/es2021/logical_assignment_operators.rs

@@ -0,0 +1,271 @@
+use std::cell::Cell;
+
+use oxc_allocator::{CloneIn, Vec};
+use oxc_ast::ast::*;
+use oxc_semantic::{ReferenceFlag, SymbolFlags};
+use oxc_span::SPAN;
+use oxc_syntax::operator::{AssignmentOperator, LogicalOperator};
+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>>>,
+}
+
+impl<'a> LogicalAssignmentOperators<'a> {
+    pub fn new(ctx: Ctx<'a>) -> Self {
+        Self { _ctx: ctx, var_declarations: vec![] }
+    }
+
+    fn clone_identifier_reference(
+        ident: &IdentifierReference<'a>,
+        ctx: &mut TraverseCtx<'a>,
+    ) -> IdentifierReference<'a> {
+        let reference = ctx.symbols().get_reference(ident.reference_id.get().unwrap());
+        let symbol_id = reference.symbol_id();
+        let flag = reference.flag();
+        ctx.create_reference_id(ident.span, ident.name.clone(), symbol_id, *flag)
+    }
+
+    pub fn maybe_generate_memoised(
+        &mut self,
+        expr: &Expression<'a>,
+        ctx: &mut TraverseCtx<'a>,
+    ) -> Option<IdentifierReference<'a>> {
+        let name = match expr {
+            Expression::Super(_) | Expression::ThisExpression(_) => return None,
+            Expression::Identifier(ident) => ident.name.clone(),
+            Expression::StringLiteral(str) => str.value.clone(),
+            _ => {
+                return None;
+            }
+        };
+
+        let symbol_id =
+            ctx.generate_uid_in_current_scope(name.as_str(), SymbolFlags::FunctionScopedVariable);
+        let symbol_name = ctx.ast.atom(ctx.symbols().get_name(symbol_id));
+
+        // var _name;
+        let binding_identifier = BindingIdentifier {
+            span: SPAN,
+            name: symbol_name.clone(),
+            symbol_id: Cell::new(Some(symbol_id)),
+        };
+        let kind = VariableDeclarationKind::Var;
+        let id = ctx.ast.binding_pattern_kind_from_binding_identifier(binding_identifier);
+        let id = ctx.ast.binding_pattern(id, None::<TSTypeAnnotation>, false);
+        self.var_declarations
+            .last_mut()
+            .unwrap()
+            .push(ctx.ast.variable_declarator(SPAN, kind, id, None, false));
+
+        // _name = name
+        Some(ctx.create_reference_id(SPAN, symbol_name, Some(symbol_id), ReferenceFlag::Write))
+    }
+
+    pub fn transform_statements(
+        &mut self,
+        _statements: &mut Vec<'a, Statement<'a>>,
+        ctx: &mut TraverseCtx<'a>,
+    ) {
+        self.var_declarations.push(ctx.ast.vec());
+    }
+
+    pub fn transform_statements_on_exit(
+        &mut self,
+        statements: &mut Vec<'a, Statement<'a>>,
+        ctx: &mut TraverseCtx<'a>,
+    ) {
+        if let Some(declarations) = self.var_declarations.pop() {
+            if declarations.is_empty() {
+                return;
+            }
+            let variable = ctx.ast.alloc_variable_declaration(
+                SPAN,
+                VariableDeclarationKind::Var,
+                declarations,
+                false,
+            );
+            statements.insert(0, Statement::VariableDeclaration(variable));
+        }
+    }
+
+    pub fn transform_expression(&mut self, expr: &mut Expression<'a>, ctx: &mut TraverseCtx<'a>) {
+        let Expression::AssignmentExpression(assignment_expr) = expr else { return };
+
+        // `&&=` `||=` `??=`
+        let operator = match assignment_expr.operator {
+            AssignmentOperator::LogicalAnd => LogicalOperator::And,
+            AssignmentOperator::LogicalOr => LogicalOperator::Or,
+            AssignmentOperator::LogicalNullish => LogicalOperator::Coalesce,
+            _ => return,
+        };
+
+        // `a &&= c` -> `a && (a = c);`
+        //               ^     ^ assign_target
+        //               ^ left_expr
+
+        let left_expr: Expression<'a>;
+        let assign_target: AssignmentTarget;
+
+        // TODO: refactor this block, add tests, cover private identifier
+        match &mut assignment_expr.left {
+            AssignmentTarget::AssignmentTargetIdentifier(ident) => {
+                left_expr = ctx.ast.expression_from_identifier_reference(
+                    Self::clone_identifier_reference(ident, ctx),
+                );
+                assign_target = AssignmentTarget::from(
+                    ctx.ast.simple_assignment_target_from_identifier_reference(
+                        Self::clone_identifier_reference(ident, ctx),
+                    ),
+                );
+            }
+            left @ match_member_expression!(AssignmentTarget) => {
+                let member_expr = left.to_member_expression_mut();
+                let op = AssignmentOperator::Assign;
+
+                // `a.b &&= c` -> `var _a; (_a = a).b && (_a.b = c)`
+                match member_expr {
+                    MemberExpression::StaticMemberExpression(static_expr) => {
+                        if let Some(ident) = self.maybe_generate_memoised(&static_expr.object, ctx)
+                        {
+                            // (_o = o).a
+                            let right = ctx.ast.move_expression(&mut static_expr.object);
+                            let target = AssignmentTarget::from(
+                                ctx.ast.simple_assignment_target_from_identifier_reference(
+                                    Self::clone_identifier_reference(&ident, ctx),
+                                ),
+                            );
+                            let object = ctx.ast.expression_assignment(SPAN, op, target, right);
+                            left_expr = Expression::from(ctx.ast.member_expression_static(
+                                SPAN,
+                                object,
+                                static_expr.property.clone_in(ctx.ast.allocator),
+                                false,
+                            ));
+
+                            // (_o.a = 1)
+                            let assign_expr = ctx.ast.member_expression_static(
+                                SPAN,
+                                ctx.ast.expression_from_identifier_reference(ident),
+                                static_expr.property.clone_in(ctx.ast.allocator),
+                                false,
+                            );
+                            assign_target = AssignmentTarget::from(
+                                ctx.ast.simple_assignment_target_member_expression(assign_expr),
+                            );
+                        } else {
+                            left_expr = Expression::from(MemberExpression::StaticMemberExpression(
+                                static_expr.clone_in(ctx.ast.allocator),
+                            ));
+                            assign_target = AssignmentTarget::from(
+                                ctx.ast.simple_assignment_target_member_expression(
+                                    member_expr.clone_in(ctx.ast.allocator),
+                                ),
+                            );
+                        };
+                    }
+                    // `a[b.y] &&= c;` ->
+                    // `var _a, _b$y; (_a = a)[_b$y = b.y] && (_a[_b$y] = c);`
+                    MemberExpression::ComputedMemberExpression(computed_expr) => {
+                        if let Some(ident) =
+                            self.maybe_generate_memoised(&computed_expr.object, ctx)
+                        {
+                            // (_o = object)
+                            let right = ctx.ast.move_expression(&mut computed_expr.object);
+                            let target = AssignmentTarget::from(
+                                ctx.ast.simple_assignment_target_from_identifier_reference(
+                                    Self::clone_identifier_reference(&ident, ctx),
+                                ),
+                            );
+                            let object = ctx.ast.expression_assignment(SPAN, op, target, right);
+
+                            let mut expression =
+                                ctx.ast.move_expression(&mut computed_expr.expression);
+
+                            // _b = expression
+                            let property = self.maybe_generate_memoised(&expression, ctx);
+
+                            if let Some(ref property) = property {
+                                let left = AssignmentTarget::from(
+                                    ctx.ast.simple_assignment_target_from_identifier_reference(
+                                        Self::clone_identifier_reference(property, ctx),
+                                    ),
+                                );
+                                expression =
+                                    ctx.ast.expression_assignment(SPAN, op, left, expression);
+                            }
+
+                            // _o[_b]
+                            assign_target =
+                                AssignmentTarget::from(ctx.ast.member_expression_computed(
+                                    SPAN,
+                                    ctx.ast.expression_from_identifier_reference(
+                                        Self::clone_identifier_reference(&ident, ctx),
+                                    ),
+                                    property.map_or_else(
+                                        || expression.clone_in(ctx.ast.allocator),
+                                        |ident| ctx.ast.expression_from_identifier_reference(ident),
+                                    ),
+                                    false,
+                                ));
+
+                            left_expr = Expression::from(
+                                ctx.ast.member_expression_computed(SPAN, object, expression, false),
+                            );
+                        } else {
+                            let property_ident =
+                                self.maybe_generate_memoised(&computed_expr.expression, ctx);
+
+                            let mut expr = computed_expr.clone_in(ctx.ast.allocator);
+                            if let Some(property_ident) = &property_ident {
+                                let left = AssignmentTarget::from(
+                                    ctx.ast.simple_assignment_target_from_identifier_reference(
+                                        property_ident.clone(),
+                                    ),
+                                );
+                                let right = computed_expr.expression.clone_in(ctx.ast.allocator);
+                                expr.expression =
+                                    ctx.ast.expression_assignment(SPAN, op, left, right);
+                            }
+                            left_expr =
+                                Expression::from(MemberExpression::ComputedMemberExpression(expr));
+
+                            let mut expr = computed_expr.clone_in(ctx.ast.allocator);
+                            if let Some(property_ident) = property_ident {
+                                expr.expression =
+                                    ctx.ast.expression_from_identifier_reference(property_ident);
+                            }
+                            assign_target = AssignmentTarget::from(
+                                ctx.ast.simple_assignment_target_member_expression(
+                                    MemberExpression::ComputedMemberExpression(expr),
+                                ),
+                            );
+                        };
+                    }
+                    MemberExpression::PrivateFieldExpression(_) => return,
+                }
+            }
+            // All other are TypeScript syntax.
+
+            // It is a Syntax Error if AssignmentTargetType of LeftHandSideExpression is not simple.
+            // So safe to return here.
+            _ => return,
+        };
+
+        let assign_op = AssignmentOperator::Assign;
+        let right = ctx.ast.move_expression(&mut assignment_expr.right);
+        let right = ctx.ast.expression_assignment(SPAN, assign_op, assign_target, right);
+
+        let logical_expr = ctx.ast.expression_logical(SPAN, left_expr, operator, right);
+
+        *expr = logical_expr;
+    }
+}

crates/oxc_transformer/src/es2021/mod.rs

@@ -0,0 +1,56 @@
+mod logical_assignment_operators;
+mod options;
+
+pub use logical_assignment_operators::LogicalAssignmentOperators;
+pub use options::ES2021Options;
+use oxc_allocator::Vec;
+use oxc_ast::ast::*;
+use oxc_traverse::TraverseCtx;
+use std::rc::Rc;
+
+use crate::context::Ctx;
+
+#[allow(dead_code)]
+pub struct ES2021<'a> {
+    ctx: Ctx<'a>,
+    options: ES2021Options,
+
+    // Plugins
+    logical_assignment_operators: LogicalAssignmentOperators<'a>,
+}
+
+impl<'a> ES2021<'a> {
+    pub fn new(options: ES2021Options, ctx: Ctx<'a>) -> Self {
+        Self {
+            logical_assignment_operators: LogicalAssignmentOperators::new(Rc::clone(&ctx)),
+            ctx,
+            options,
+        }
+    }
+
+    pub fn transform_statements(
+        &mut self,
+        statements: &mut Vec<'a, Statement<'a>>,
+        ctx: &mut TraverseCtx<'a>,
+    ) {
+        if self.options.logical_assignment_operators {
+            self.logical_assignment_operators.transform_statements(statements, ctx);
+        }
+    }
+
+    pub fn transform_statements_on_exit(
+        &mut self,
+        statements: &mut Vec<'a, Statement<'a>>,
+        ctx: &mut TraverseCtx<'a>,
+    ) {
+        if self.options.logical_assignment_operators {
+            self.logical_assignment_operators.transform_statements_on_exit(statements, ctx);
+        }
+    }
+
+    pub fn transform_expression(&mut self, expr: &mut Expression<'a>, ctx: &mut TraverseCtx<'a>) {
+        if self.options.logical_assignment_operators {
+            self.logical_assignment_operators.transform_expression(expr, ctx);
+        }
+    }
+}

crates/oxc_transformer/src/es2021/options.rs

@@ -0,0 +1,16 @@
+use serde::Deserialize;
+
+#[derive(Debug, Default, Clone, Deserialize)]
+#[serde(default, rename_all = "camelCase", deny_unknown_fields)]
+pub struct ES2021Options {
+    #[serde(skip)]
+    pub logical_assignment_operators: bool,
+}
+
+impl ES2021Options {
+    #[must_use]
+    pub fn with_logical_assignment_operators(mut self, enable: bool) -> Self {
+        self.logical_assignment_operators = enable;
+        self
+    }
+}

crates/oxc_transformer/src/lib.rs

@@ -18,6 +18,7 @@ mod es2015;
 mod es2016;
 mod es2019;
 mod es2020;
+mod es2021;
 mod react;
 mod typescript;
 
@@ -31,6 +32,7 @@ use std::{path::Path, rc::Rc};
 use es2016::ES2016;
 use es2019::ES2019;
 use es2020::ES2020;
+use es2021::ES2021;
 use oxc_allocator::{Allocator, Vec};
 use oxc_ast::{ast::*, AstBuilder, Trivias};
 use oxc_diagnostics::OxcDiagnostic;
@@ -64,6 +66,7 @@ pub struct Transformer<'a> {
     // NOTE: all callbacks must run in order.
     x0_typescript: TypeScript<'a>,
     x1_react: React<'a>,
+    x2_es2021: ES2021<'a>,
     x2_es2020: ES2020<'a>,
     x2_es2019: ES2019<'a>,
     x2_es2016: ES2016<'a>,
@@ -91,6 +94,7 @@ 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_es2021: ES2021::new(options.es2021, 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)),
@@ -172,6 +176,7 @@ impl<'a> Traverse<'a> for Transformer<'a> {
     fn enter_expression(&mut self, expr: &mut Expression<'a>, ctx: &mut TraverseCtx<'a>) {
         self.x0_typescript.transform_expression(expr);
         self.x1_react.transform_expression(expr, ctx);
+        self.x2_es2021.transform_expression(expr, ctx);
         self.x2_es2020.transform_expression(expr, ctx);
         self.x2_es2016.transform_expression(expr, ctx);
         self.x3_es2015.transform_expression(expr);
@@ -260,6 +265,7 @@ impl<'a> Traverse<'a> for Transformer<'a> {
 
     fn enter_statements(&mut self, stmts: &mut Vec<'a, Statement<'a>>, ctx: &mut TraverseCtx<'a>) {
         self.x0_typescript.transform_statements(stmts);
+        self.x2_es2021.transform_statements(stmts, ctx);
         self.x2_es2020.transform_statements(stmts, ctx);
         self.x2_es2016.transform_statements(stmts, ctx);
         self.x3_es2015.enter_statements(stmts);
@@ -267,6 +273,7 @@ impl<'a> Traverse<'a> for Transformer<'a> {
 
     fn exit_statements(&mut self, stmts: &mut Vec<'a, Statement<'a>>, ctx: &mut TraverseCtx<'a>) {
         self.x0_typescript.transform_statements_on_exit(stmts, ctx);
+        self.x2_es2021.transform_statements_on_exit(stmts, ctx);
         self.x2_es2020.transform_statements_on_exit(stmts, ctx);
         self.x2_es2016.transform_statements_on_exit(stmts, ctx);
         self.x3_es2015.exit_statements(stmts);

crates/oxc_transformer/src/options/transformer.rs

@@ -10,6 +10,7 @@ use crate::{
     es2016::ES2016Options,
     es2019::ES2019Options,
     es2020::ES2020Options,
+    es2021::ES2021Options,
     options::babel::BabelOptions,
     react::ReactOptions,
     typescript::TypeScriptOptions,
@@ -43,6 +44,8 @@ pub struct TransformOptions {
     pub es2019: ES2019Options,
 
     pub es2020: ES2020Options,
+
+    pub es2021: ES2021Options,
 }
 
 impl TransformOptions {
@@ -128,6 +131,11 @@ impl TransformOptions {
             enable_plugin(plugin_name, options, &env_options, &targets).is_some()
         });
 
+        let es2021 = ES2021Options::default().with_logical_assignment_operators({
+            let plugin_name = "transform-logical-assignment-operators";
+            enable_plugin(plugin_name, options, &env_options, &targets).is_some()
+        });
+
         let typescript = {
             let plugin_name = "transform-typescript";
             from_value::<TypeScriptOptions>(get_plugin_options(plugin_name, options))
@@ -162,6 +170,7 @@ impl TransformOptions {
             es2016,
             es2019,
             es2020,
+            es2021,
         })
     }
 }

tasks/transform_conformance/babel.snap.md

@@ -1,6 +1,6 @@
 commit: 12619ffe
 
-Passed: 462/947
+Passed: 466/953
 
 # All Passed:
 * babel-plugin-transform-optional-catch-binding
@@ -434,6 +434,10 @@ Passed: 462/947
 * shipped-proposals/new-class-features-chrome-94/input.js
 * shipped-proposals/new-class-features-firefox-70/input.js
 
+# babel-plugin-transform-logical-assignment-operators (4/6)
+* logical-assignment/general-semantics/input.js
+* logical-assignment/null-coalescing/input.js
+
 # babel-plugin-transform-nullish-coalescing-operator (2/12)
 * assumption-noDocumentAll/transform/input.js
 * assumption-noDocumentAll/transform-in-default-destructuring/input.js

tasks/transform_conformance/babel_exec.snap.md

@@ -1,6 +1,6 @@
 commit: 12619ffe
 
-Passed: 13/19
+Passed: 16/23
 
 # All Passed:
 * babel-plugin-transform-nullish-coalescing-operator
@@ -15,6 +15,9 @@ Passed: 13/19
 * sanity/check-es2015-constants/exec.js
 * sanity/regex-dot-all/exec.js
 
+# babel-plugin-transform-logical-assignment-operators (3/4)
+* logical-assignment/null-coalescing/exec.js
+
 # babel-plugin-transform-react-jsx-source (0/2)
 * react-source/basic-sample/exec.js
 * react-source/with-source/exec.js

tasks/transform_conformance/src/constants.rs

@@ -8,10 +8,10 @@ pub(crate) const PLUGINS: &[&str] = &[
     // "babel-plugin-transform-private-methods",
     // "babel-plugin-transform-private-property-in-object",
     // // [Syntax] "babel-plugin-transform-syntax-top-level-await",
-    // // ES2021
+    // ES2021
-    // "babel-plugin-transform-logical-assignment-operators",
+    "babel-plugin-transform-logical-assignment-operators",
     // "babel-plugin-transform-numeric-separator",
-    // // ES2020
+    // ES2020
     // "babel-plugin-transform-export-namespace-from",
     // "babel-plugin-transform-dynamic-import",
     "babel-plugin-transform-nullish-coalescing-operator",
@@ -19,7 +19,7 @@ pub(crate) const PLUGINS: &[&str] = &[
     // // [Syntax] "babel-plugin-transform-syntax-bigint",
     // // [Syntax] "babel-plugin-transform-syntax-dynamic-import",
     // // [Syntax] "babel-plugin-transform-syntax-import-meta",
-    // // ES2019
+    // ES2019
     "babel-plugin-transform-optional-catch-binding",
     // "babel-plugin-transform-json-strings",
     // // ES2018
@@ -32,7 +32,7 @@ pub(crate) const PLUGINS: &[&str] = &[
     // "babel-plugin-transform-async-to-generator",
     // ES2016
     "babel-plugin-transform-exponentiation-operator",
-    // // ES2015
+    // ES2015
     "babel-plugin-transform-arrow-functions",
     // "babel-plugin-transform-function-name",
     // "babel-plugin-transform-shorthand-properties",