From daf60872ed3017a30ceef768cb06642d4ec7d649 Mon Sep 17 00:00:00 2001
From: overlookmotel <557937+overlookmotel@users.noreply.github.com>
Date: Thu, 10 Jul 2025 16:13:14 +0000
Subject: [PATCH] perf(transformer/styled-components): generate file path hash
 in `InlineString` (#12196)

Use an `InlineString` to build the file path hash, instead of a `Vec`. For short strings like this, `InlineString` is cheaper to build and involves no allocations.

Also, don't store this temporary value in arena.
---
 crates/oxc_transformer/Cargo.toml             |  2 +-
 .../src/plugins/styled_components.rs          | 37 +++++++++----------
 2 files changed, 19 insertions(+), 20 deletions(-)

diff --git a/crates/oxc_transformer/Cargo.toml b/crates/oxc_transformer/Cargo.toml
index a4669e45d3e85..85d32f6562211 100644
--- a/crates/oxc_transformer/Cargo.toml
+++ b/crates/oxc_transformer/Cargo.toml
@@ -25,7 +25,7 @@ oxc-browserslist = { workspace = true }
 oxc_allocator = { workspace = true }
 oxc_ast = { workspace = true }
 oxc_ast_visit = { workspace = true }
-oxc_data_structures = { workspace = true, features = ["rope", "stack"] }
+oxc_data_structures = { workspace = true, features = ["inline_string", "rope", "stack"] }
 oxc_diagnostics = { workspace = true }
 oxc_ecmascript = { workspace = true }
 oxc_parser = { workspace = true }
diff --git a/crates/oxc_transformer/src/plugins/styled_components.rs b/crates/oxc_transformer/src/plugins/styled_components.rs
index 81d7020f1d004..b0543ca10c5c4 100644
--- a/crates/oxc_transformer/src/plugins/styled_components.rs
+++ b/crates/oxc_transformer/src/plugins/styled_components.rs
@@ -55,13 +55,17 @@
 //! - Babel plugin: <https://github.com/styled-components/babel-plugin-styled-components>
 //! - Documentation: <https://styled-components.com/docs/tooling#babel-plugin>
 
-use rustc_hash::FxHashSet;
-use serde::Deserialize;
+use std::{
+    hash::{Hash, Hasher},
+    iter::once,
+};
 
-use std::iter::once;
+use rustc_hash::{FxHashSet, FxHasher};
+use serde::Deserialize;
 
 use oxc_allocator::{StringBuilder, TakeIn, Vec as ArenaVec};
 use oxc_ast::{AstBuilder, NONE, ast::*};
+use oxc_data_structures::inline_string::InlineString;
 use oxc_semantic::SymbolId;
 use oxc_span::SPAN;
 use oxc_traverse::{Ancestor, Traverse};
@@ -637,7 +641,7 @@ impl<'a> StyledComponents<'a, '_> {
                 String::with_capacity(PREFIX_LEN)
             };
 
-            prefix.extend(["sc-", self.get_file_hash(ctx), "-"]);
+            prefix.extend(["sc-", self.get_file_hash().as_str(), "-"]);
 
             self.component_id_prefix = Some(prefix);
             self.component_id_prefix.as_deref().unwrap()
@@ -651,27 +655,22 @@ impl<'a> StyledComponents<'a, '_> {
     }
 
     /// Generates a unique file hash based on the source path or source code.
-    fn get_file_hash(&self, ctx: &TraverseCtx<'a>) -> &'a str {
-        use rustc_hash::FxHasher;
-        use std::hash::{Hash, Hasher};
-
+    fn get_file_hash(&self) -> InlineString<7, u8> {
         #[inline]
-        fn base36_encode<'a>(mut num: u64, ctx: &TraverseCtx<'a>) -> &'a str {
-            const BASE36_BYTES: &[u8] = b"abcdefghijklmnopqrstuvwxyz0123456789";
+        fn base36_encode(mut num: u64) -> InlineString<7, u8> {
+            const BASE36_BYTES: &[u8; 36] = b"abcdefghijklmnopqrstuvwxyz0123456789";
 
             num %= 36_u64.pow(6); // 36^6, to ensure the result is <= 6 characters long.
 
-            let mut result = Vec::with_capacity(6);
-
+            let mut str = InlineString::new();
             while num != 0 {
-                result.push(BASE36_BYTES[(num % 36) as usize]);
+                // SAFETY: `num < 36.pow(6)` to start with, is and divided by 36 on each turn of loop,
+                // so we cannot push more than 6 bytes. Capacity of `InlineString` is 7.
+                // All bytes in `BASE36_BYTES` are ASCII.
+                unsafe { str.push_unchecked(BASE36_BYTES[(num % 36) as usize]) };
                 num /= 36;
             }
-
-            ctx.ast.allocator.alloc_str(
-                // SAFETY: the bytes are valid UTF-8 as they are ASCII characters.
-                unsafe { std::str::from_utf8_unchecked(&result) },
-            )
+            str
         }
 
         let mut hasher = FxHasher::default();
@@ -681,7 +680,7 @@ impl<'a> StyledComponents<'a, '_> {
             self.ctx.source_text.hash(&mut hasher);
         }
 
-        base36_encode(hasher.finish(), ctx)
+        base36_encode(hasher.finish())
     }
 
     /// Returns the display name which infers the component name or gets from the file name.