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refactor(transformer): shared
VarDeclarations (#6170)
First step towards #5049. Various transforms need to add a `var` statement at top of enclosing statement block. e.g.: ```js // Input a ??= b; ``` ```js // Output var _a; (_a = a) !== null && _a !== void 0 ? _a : (a = b); ``` Each of these transforms previously maintained it's own stack and added `var` statements individually. Share this functionality in a "common" utility transform which maintains a single stack to serve them all.
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,37 @@ | ||
| //! Utility transforms which are in common between other transforms. | ||
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| use oxc_allocator::Vec; | ||
| use oxc_ast::ast::*; | ||
| use oxc_traverse::{Traverse, TraverseCtx}; | ||
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| use crate::TransformCtx; | ||
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| mod var_declarations; | ||
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| use var_declarations::VarDeclarations; | ||
| pub use var_declarations::VarDeclarationsStore; | ||
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| pub struct Common<'a, 'ctx> { | ||
| var_declarations: VarDeclarations<'a, 'ctx>, | ||
| } | ||
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| impl<'a, 'ctx> Common<'a, 'ctx> { | ||
| pub fn new(ctx: &'ctx TransformCtx<'a>) -> Self { | ||
| Self { var_declarations: VarDeclarations::new(ctx) } | ||
| } | ||
| } | ||
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| impl<'a, 'ctx> Traverse<'a> for Common<'a, 'ctx> { | ||
| #[inline] // Inline because it's no-op in release mode | ||
| fn exit_program(&mut self, program: &mut Program<'a>, ctx: &mut TraverseCtx<'a>) { | ||
| self.var_declarations.exit_program(program, ctx); | ||
| } | ||
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| fn enter_statements(&mut self, stmts: &mut Vec<'a, Statement<'a>>, ctx: &mut TraverseCtx<'a>) { | ||
| self.var_declarations.enter_statements(stmts, ctx); | ||
| } | ||
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| fn exit_statements(&mut self, stmts: &mut Vec<'a, Statement<'a>>, ctx: &mut TraverseCtx<'a>) { | ||
| self.var_declarations.exit_statements(stmts, ctx); | ||
| } | ||
| } |
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,111 @@ | ||
| //! Utility transform to add `var` declarations to top of statement blocks. | ||
| //! | ||
| //! `VarDeclarationsStore` contains a stack of `Vec<VariableDeclarator>`s. | ||
| //! It is stored on `TransformCtx`. | ||
| //! | ||
| //! `VarDeclarations` transform pushes an empty entry onto this stack when entering a statement block, | ||
| //! and when exiting the block, writes a `var` statement to top of block containing the declarators. | ||
| //! | ||
| //! Other transforms can add declarators to the store by calling methods of `VarDeclarationsStore`: | ||
| //! | ||
| //! ```rs | ||
| //! self.ctx.var_declarations.insert_declarator(name, symbol_id, None, ctx); | ||
| //! ``` | ||
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| use std::cell::RefCell; | ||
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| use oxc_allocator::Vec; | ||
| use oxc_ast::{ast::*, NONE}; | ||
| use oxc_span::SPAN; | ||
| use oxc_syntax::symbol::SymbolId; | ||
| use oxc_traverse::{Traverse, TraverseCtx}; | ||
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| use crate::{context::TransformCtx, helpers::stack::SparseStack}; | ||
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| /// Transform that maintains the stack of `Vec<VariableDeclarator>`s, and adds a `var` statement | ||
| /// to top of a statement block if another transform has requested that. | ||
| /// | ||
| /// Must run after all other transforms. | ||
| pub struct VarDeclarations<'a, 'ctx> { | ||
| ctx: &'ctx TransformCtx<'a>, | ||
| } | ||
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| impl<'a, 'ctx> VarDeclarations<'a, 'ctx> { | ||
| pub fn new(ctx: &'ctx TransformCtx<'a>) -> Self { | ||
| Self { ctx } | ||
| } | ||
| } | ||
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| impl<'a, 'ctx> Traverse<'a> for VarDeclarations<'a, 'ctx> { | ||
| #[inline] // Inline because it's no-op in release mode | ||
| fn exit_program(&mut self, _program: &mut Program<'a>, _ctx: &mut TraverseCtx<'a>) { | ||
| let declarators = self.ctx.var_declarations.declarators.borrow(); | ||
| debug_assert!(declarators.len() == 1); | ||
| debug_assert!(declarators.last().is_none()); | ||
| } | ||
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| fn enter_statements( | ||
| &mut self, | ||
| _stmts: &mut Vec<'a, Statement<'a>>, | ||
| _ctx: &mut TraverseCtx<'a>, | ||
| ) { | ||
| let mut declarators = self.ctx.var_declarations.declarators.borrow_mut(); | ||
| declarators.push(None); | ||
| } | ||
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| fn exit_statements(&mut self, stmts: &mut Vec<'a, Statement<'a>>, ctx: &mut TraverseCtx<'a>) { | ||
| let mut declarators = self.ctx.var_declarations.declarators.borrow_mut(); | ||
| if let Some(declarators) = declarators.pop() { | ||
| debug_assert!(!declarators.is_empty()); | ||
| let variable = ctx.ast.alloc_variable_declaration( | ||
| SPAN, | ||
| VariableDeclarationKind::Var, | ||
| declarators, | ||
| false, | ||
| ); | ||
| stmts.insert(0, Statement::VariableDeclaration(variable)); | ||
| } | ||
| } | ||
| } | ||
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| /// Store for `VariableDeclarator`s to be added to enclosing statement block. | ||
| pub struct VarDeclarationsStore<'a> { | ||
| declarators: RefCell<SparseStack<Vec<'a, VariableDeclarator<'a>>>>, | ||
| } | ||
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| impl<'a> VarDeclarationsStore<'a> { | ||
| pub fn new() -> Self { | ||
| Self { declarators: RefCell::new(SparseStack::new()) } | ||
| } | ||
| } | ||
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| impl<'a> VarDeclarationsStore<'a> { | ||
| /// Add a `VariableDeclarator` to be inserted at top of current enclosing statement block, | ||
| /// given `name` and `symbol_id`. | ||
| pub fn insert_declarator( | ||
| &self, | ||
| name: Atom<'a>, | ||
| symbol_id: SymbolId, | ||
| init: Option<Expression<'a>>, | ||
| ctx: &mut TraverseCtx<'a>, | ||
| ) { | ||
| let ident = BindingIdentifier::new_with_symbol_id(SPAN, name, symbol_id); | ||
| let ident = ctx.ast.binding_pattern_kind_from_binding_identifier(ident); | ||
| let ident = ctx.ast.binding_pattern(ident, NONE, false); | ||
| self.insert_declarator_binding_pattern(ident, init, ctx); | ||
| } | ||
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| /// Add a `VariableDeclarator` to be inserted at top of current enclosing statement block, | ||
| /// given a `BindingPattern`. | ||
| pub fn insert_declarator_binding_pattern( | ||
| &self, | ||
| ident: BindingPattern<'a>, | ||
| init: Option<Expression<'a>>, | ||
| ctx: &mut TraverseCtx<'a>, | ||
| ) { | ||
| let declarator = | ||
| ctx.ast.variable_declarator(SPAN, VariableDeclarationKind::Var, ident, init, false); | ||
| let mut declarators = self.declarators.borrow_mut(); | ||
| declarators.last_mut_or_init(|| ctx.ast.vec()).push(declarator); | ||
| } | ||
| } |
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