perf(parser): replace dragonbox_ecma with zmij_ecma (#28282)

Use `zmij_ecma` to reduce float-formatting time while preserving
ECMAScript output. Local Apple M4 Pro measurements showed 21–66% less
conversion time and about 18% less time generating synthetic
numeric-heavy JavaScript; real-world bundles were roughly unchanged.

AI-assisted with Codex.

Cargo.lock

@@ -592,12 +592,6 @@ dependencies = [
  "litrs",
 ]
 
-[[package]]
-name = "dragonbox_ecma"
-version = "0.1.12"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "fd8e701084c37e7ef62d3f9e453b618130cbc0ef3573847785952a3ac3f746bf"
-
 [[package]]
 name = "dyn-clone"
 version = "1.0.20"
@@ -2012,7 +2006,6 @@ name = "oxc_ecmascript"
 version = "0.156.0"
 dependencies = [
  "cow-utils",
- "dragonbox_ecma",
  "itoa",
  "memchr",
  "num-bigint",
@@ -2026,15 +2019,16 @@ dependencies = [
  "oxc_str",
  "oxc_syntax",
  "smallvec",
+ "zmij_ecma",
 ]
 
 [[package]]
 name = "oxc_estree"
 version = "0.156.0"
 dependencies = [
- "dragonbox_ecma",
  "itoa",
  "oxc_data_structures",
+ "zmij_ecma",
 ]
 
 [[package]]
@@ -2133,7 +2127,6 @@ dependencies = [
 name = "oxc_formatter_json"
 version = "0.75.0"
 dependencies = [
- "dragonbox_ecma",
  "insta",
  "oxc_allocator",
  "oxc_ast",
@@ -2146,6 +2139,7 @@ dependencies = [
  "oxc_syntax",
  "oxc_tasks_common",
  "pico-args",
+ "zmij_ecma",
 ]
 
 [[package]]
@@ -2691,7 +2685,6 @@ version = "0.156.0"
 dependencies = [
  "bitflags",
  "cow-utils",
- "dragonbox_ecma",
  "nonmax",
  "oxc_allocator",
  "oxc_ast_macros",
@@ -2702,6 +2695,7 @@ dependencies = [
  "phf",
  "serde",
  "unicode-id-start",
+ "zmij_ecma",
 ]
 
 [[package]]
@@ -4667,3 +4661,9 @@ name = "zmij"
 version = "1.0.21"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "b8848ee67ecc8aedbaf3e4122217aff892639231befc6a1b58d29fff4c2cabaa"
+
+[[package]]
+name = "zmij_ecma"
+version = "1.0.23"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "458b3e7a977f14499066b6bdb63d69da30ce337d6c160f077e6c575c82a44db9"

Cargo.toml

@@ -215,7 +215,6 @@ constcat = "0.6.1" # Const string concatenation
 convert_case = "0.12.0" # Case conversion
 cow-utils = "0.1.3" # Copy-on-write utilities
 criterion2 = { version = "3.0.4", default-features = false } # Benchmarking
-dragonbox_ecma = "0.1.12" # Fast float formatting
 editorconfig-parser = "0.0.4" # EditorConfig parsing
 encoding_rs = "0.8.35" # Character encoding
 encoding_rs_io = "0.1.7" # Encoding I/O
@@ -281,6 +280,7 @@ ureq = { version = "3.3.0", default-features = false } # HTTP client
 url = { version = "2.5.8" } # URL parsing
 walkdir = "2.5.0" # Directory traversal
 windows-sys = { version = "0.61.2" } # Windows API bindings
+zmij_ecma = "1.0.23" # Fast float formatting
 
 [workspace.metadata.cargo-shear]
 ignored = [

crates/oxc_ecmascript/Cargo.toml

@@ -35,12 +35,12 @@ oxc_str = { workspace = true }
 oxc_syntax = { workspace = true, features = ["to_js_string"] }
 
 cow-utils = { workspace = true, optional = true }
-dragonbox_ecma = { workspace = true }
 itoa = { workspace = true }
 memchr = { workspace = true }
 num-bigint = { workspace = true }
 num-traits = { workspace = true }
 smallvec = { workspace = true, optional = true }
+zmij_ecma = { workspace = true }
 
 [dev-dependencies]
 oxc_allocator = { workspace = true }

crates/oxc_ecmascript/src/number_literal.rs

@@ -18,7 +18,7 @@ pub fn with_number_literal<R>(value: f64, f: impl FnOnce(&str) -> R) -> R {
 
 #[expect(clippy::cast_possible_truncation, clippy::cast_sign_loss, clippy::cast_possible_wrap)]
 fn number_literal(value: f64) -> LiteralString {
-    let mut buffer = dragonbox_ecma::Buffer::new();
+    let mut buffer = zmij_ecma::Buffer::new();
     let formatted = buffer.format(value);
     let mut best_candidate = LiteralString::new();
     for (index, byte) in formatted.bytes().enumerate() {

crates/oxc_estree/Cargo.toml

@@ -22,12 +22,12 @@ oxc_data_structures = { workspace = true, features = [
   "stack",
 ], optional = true }
 
-dragonbox_ecma = { workspace = true, optional = true }
 itoa = { workspace = true, optional = true }
+zmij_ecma = { workspace = true, optional = true }
 
 [features]
 default = []
-serialize = ["dep:oxc_data_structures", "dep:itoa", "dep:dragonbox_ecma"]
+serialize = ["dep:oxc_data_structures", "dep:itoa", "dep:zmij_ecma"]
 
 [lib]
 doctest = false

crates/oxc_estree/src/serialize/primitives.rs

@@ -1,5 +1,5 @@
-use dragonbox_ecma::Buffer as DragonboxBuffer;
 use itoa::Buffer as ItoaBuffer;
+use zmij_ecma::Buffer as ZmijBuffer;
 
 use super::{ESTree, Serializer};
 
@@ -14,7 +14,7 @@ impl ESTree for bool {
 impl ESTree for f64 {
     fn serialize<S: Serializer>(&self, mut serializer: S) {
         if self.is_finite() {
-            let mut buffer = DragonboxBuffer::new();
+            let mut buffer = ZmijBuffer::new();
             let s = buffer.format_finite(*self);
             serializer.buffer_mut().print_str(s);
         } else if self.is_nan() {

crates/oxc_formatter_json/Cargo.toml

@@ -17,7 +17,6 @@ description.workspace = true
 workspace = true
 
 [dependencies]
-dragonbox_ecma = { workspace = true }
 oxc_allocator = { workspace = true }
 oxc_ast = { workspace = true }
 oxc_diagnostics = { workspace = true }
@@ -27,6 +26,8 @@ oxc_span = { workspace = true }
 oxc_str = { workspace = true }
 oxc_syntax = { workspace = true }
 
+zmij_ecma = { workspace = true }
+
 [dev-dependencies]
 insta = { workspace = true }
 oxc_formatter_tests = { workspace = true, features = ["conformance"] }

crates/oxc_formatter_json/src/print/mod.rs

@@ -44,12 +44,12 @@ pub fn write_quoted_str<'a>(f: &mut JsonFormatter<'_, 'a>, quote_byte: u8, body:
 /// JS stringifies the parsed value into a different shape (`"16"` for `0x10`, `"NaN"` for `1_2`),
 /// Rust simply fails to parse, so `Err` mapping to `false` matches.
 pub fn number_string_round_trips(s: &str) -> bool {
-    // PERF: Use `dragonbox_ecma` directly instead of `oxc_syntax::ToJsString`
+    // PERF: Use `zmij_ecma` directly instead of `oxc_syntax::ToJsString`
     // The latter returns `String` (heap alloc),
     // while `Buffer::format` returns `&str` borrowed from a stack buffer.
     // This is only a `==` comparison on a hot path (every numeric key), so avoid the alloc.
     s.parse::<f64>()
-        .is_ok_and(|value| value.is_finite() && dragonbox_ecma::Buffer::new().format(value) == s)
+        .is_ok_and(|value| value.is_finite() && zmij_ecma::Buffer::new().format(value) == s)
 }
 
 /// Wraps a re-entrant JSON closure in a [`FormatWith`]. The closure's context is

crates/oxc_syntax/Cargo.toml

@@ -33,10 +33,10 @@ nonmax = { workspace = true }
 phf = { workspace = true, features = ["macros"] }
 unicode-id-start = { workspace = true }
 
-dragonbox_ecma = { workspace = true, optional = true }
 serde = { workspace = true, features = ["derive"], optional = true }
+zmij_ecma = { workspace = true, optional = true }
 
 [features]
 default = []
-to_js_string = ["dep:dragonbox_ecma"]
+to_js_string = ["dep:zmij_ecma"]
 serialize = ["bitflags/serde", "dep:serde", "oxc_estree/serialize"]

crates/oxc_syntax/src/number.rs

@@ -44,7 +44,7 @@ pub trait ToJsString {
 #[cfg(feature = "to_js_string")]
 impl ToJsString for f64 {
     fn to_js_string(&self) -> String {
-        let mut buffer = dragonbox_ecma::Buffer::new();
+        let mut buffer = zmij_ecma::Buffer::new();
         buffer.format(*self).to_string()
     }
 }