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feat(transformer): ES2020 Nullish Coalescing Operator
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,3 @@ | ||
| mod nullish_coalescing_operator; | ||
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| pub use nullish_coalescing_operator::NullishCoalescingOperator; |
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crates/oxc_transformer/src/es2020/nullish_coalescing_operator.rs
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,88 @@ | ||
| use std::{cell::RefCell, rc::Rc}; | ||
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| use oxc_allocator::Vec; | ||
| use oxc_ast::{ast::*, AstBuilder}; | ||
| use oxc_semantic::SymbolTable; | ||
| use oxc_span::Span; | ||
| use oxc_syntax::operator::{AssignmentOperator, BinaryOperator, LogicalOperator}; | ||
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| use crate::{options::Assumptions, utils::CreateVars}; | ||
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| /// ES2020: Nullish Coalescing Operator | ||
| /// | ||
| /// References: | ||
| /// * <https://babeljs.io/docs/babel-plugin-transform-nullish-coalescing-operator> | ||
| /// * <https://github.com/babel/babel/tree/main/packages/babel-plugin-transform-nullish-coalescing-operator> | ||
| pub struct NullishCoalescingOperator<'a> { | ||
| ast: Rc<AstBuilder<'a>>, | ||
| symbols: Rc<RefCell<SymbolTable>>, | ||
| assumptions: Assumptions, | ||
| vars: Vec<'a, VariableDeclarator<'a>>, | ||
| } | ||
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| impl<'a> CreateVars<'a> for NullishCoalescingOperator<'a> { | ||
| fn ast(&self) -> &AstBuilder<'a> { | ||
| &self.ast | ||
| } | ||
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| fn vars_mut(&mut self) -> &mut Vec<'a, VariableDeclarator<'a>> { | ||
| &mut self.vars | ||
| } | ||
| } | ||
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| impl<'a> NullishCoalescingOperator<'a> { | ||
| pub fn new( | ||
| ast: Rc<AstBuilder<'a>>, | ||
| symbols: Rc<RefCell<SymbolTable>>, | ||
| assumptions: Assumptions, | ||
| ) -> Self { | ||
| let vars = ast.new_vec(); | ||
| Self { ast, symbols, assumptions, vars } | ||
| } | ||
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| pub fn transform_expression(&mut self, expr: &mut Expression<'a>) { | ||
| // left ?? right | ||
| let Expression::LogicalExpression(logical_expr) = expr else { return }; | ||
| if logical_expr.operator != LogicalOperator::Coalesce { | ||
| return; | ||
| } | ||
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| let span = Span::default(); | ||
| let reference; | ||
| let assignment; | ||
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| // skip creating extra reference when `left` is static | ||
| if self.symbols.borrow().is_static(&logical_expr.left) { | ||
| reference = self.ast.copy(&logical_expr.left); | ||
| assignment = self.ast.copy(&logical_expr.left); | ||
| } else { | ||
| let name = self.create_new_var(&logical_expr.left); | ||
| let ident = IdentifierReference::new(span, name); | ||
| reference = self.ast.identifier_reference_expression(ident.clone()); | ||
| let left = AssignmentTarget::SimpleAssignmentTarget( | ||
| self.ast.simple_assignment_target_identifier(ident), | ||
| ); | ||
| let right = self.ast.copy(&logical_expr.left); | ||
| assignment = | ||
| self.ast.assignment_expression(span, AssignmentOperator::Assign, left, right); | ||
| }; | ||
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| let test = if self.assumptions.no_document_all { | ||
| let null = self.ast.literal_null_expression(NullLiteral::new(span)); | ||
| self.ast.binary_expression(span, assignment, BinaryOperator::Inequality, null) | ||
| } else { | ||
| let op = BinaryOperator::StrictInequality; | ||
| let null = self.ast.literal_null_expression(NullLiteral::new(span)); | ||
| let left = self.ast.binary_expression(span, self.ast.copy(&assignment), op, null); | ||
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| let right = | ||
| self.ast.binary_expression(span, self.ast.copy(&reference), op, self.ast.void_0()); | ||
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| self.ast.logical_expression(span, left, LogicalOperator::And, right) | ||
| }; | ||
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| let right = self.ast.move_expression(&mut logical_expr.right); | ||
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| *expr = self.ast.conditional_expression(span, test, reference, right); | ||
| } | ||
| } |
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