From 4f6dc22a3818e983c3bc5aa82cf73b383932d9c9 Mon Sep 17 00:00:00 2001
From: overlookmotel <557937+overlookmotel@users.noreply.github.com>
Date: Wed, 23 Oct 2024 13:26:23 +0000
Subject: [PATCH] refactor(transformer/react-refresh): avoid re-creating
 `Atom`s (#6816)

Store `BoundIdentifier` in `registrations`. This allows removing the call to `ctx.ast.atom()` which re-allocates a new `Atom` into the arena - unnecessary as it's already been allocated when the UID was created.

It's unfortunate that `Semantic` stores symbol names as `CompactStr`s instead of `Atom`s, otherwise we could get the name as an `Atom` without re-allocating it. Hopefully we can make that change in future, and then reduce `BoundIdentifier` to just contain the `SymbolId`. But for now, we are kind of stuck with it.
---
 crates/oxc_transformer/src/react/refresh.rs | 11 +++++------
 1 file changed, 5 insertions(+), 6 deletions(-)

diff --git a/crates/oxc_transformer/src/react/refresh.rs b/crates/oxc_transformer/src/react/refresh.rs
index 8d37e51af9ba6..6119eb7f83ebb 100644
--- a/crates/oxc_transformer/src/react/refresh.rs
+++ b/crates/oxc_transformer/src/react/refresh.rs
@@ -102,7 +102,7 @@ pub struct ReactRefresh<'a, 'ctx> {
     emit_full_signatures: bool,
     ctx: &'ctx TransformCtx<'a>,
     // States
-    registrations: Vec<(SymbolId, Atom<'a>)>,
+    registrations: Vec<(BoundIdentifier<'a>, Atom<'a>)>,
     signature_declarator_items: Vec<oxc_allocator::Vec<'a, VariableDeclarator<'a>>>,
     /// Used to wrap call expression with signature.
     /// (eg: hoc(() => {}) -> _s1(hoc(_s1(() => {}))))
@@ -154,9 +154,7 @@ impl<'a, 'ctx> Traverse<'a> for ReactRefresh<'a, 'ctx> {
 
         let mut variable_declarator_items = ctx.ast.vec_with_capacity(self.registrations.len());
         let mut new_statements = ctx.ast.vec_with_capacity(self.registrations.len() + 1);
-        for (symbol_id, persistent_id) in self.registrations.drain(..) {
-            let name = ctx.ast.atom(ctx.symbols().get_name(symbol_id));
-            let binding = BoundIdentifier::new(name, symbol_id);
+        for (binding, persistent_id) in self.registrations.drain(..) {
             variable_declarator_items.push(ctx.ast.variable_declarator(
                 SPAN,
                 VariableDeclarationKind::Var,
@@ -451,8 +449,9 @@ impl<'a, 'ctx> ReactRefresh<'a, 'ctx> {
         ctx: &mut TraverseCtx<'a>,
     ) -> AssignmentTarget<'a> {
         let binding = ctx.generate_uid_in_root_scope("c", SymbolFlags::FunctionScopedVariable);
-        self.registrations.push((binding.symbol_id, persistent_id));
-        binding.create_target(reference_flags, ctx)
+        let target = binding.create_target(reference_flags, ctx);
+        self.registrations.push((binding, persistent_id));
+        target
     }
 
     /// Similar to the `findInnerComponents` function in `react-refresh/babel`.