lightningcss vs rust-cssparser compile times

This repository compares the compile time costs of lightningcss and cssparser.

Related lightningcss issue: parcel-bundler/lightningcss#357

git clone git@github.com:chinedufn/rust-cssparser-and-lightningcss-compile-times.git
./run.sh

Sample output:

Device	Processor	Memory
MacBook Pro (2019, 16 inch)	Processor: 2.4 GHz 8-Core Intel Core i9	Memory: 64 GB 2667 MHz DDR4

Debug Build

(lightningcss compiles ~4x slower than rust-cssparser)

rust-cssparser debug build timing
real 0m11.188s user 0m29.876s sys 0m3.621s

lightningcss debug build timing
real 0m40.468s user 2m40.552s sys 0m16.839s

Release Build

(lightningcss compiles ~7x slower than rust-cssparser)

rust-cssparser release build time
real 0m9.391s user 0m25.043s sys 0m3.294s

lightningcss release build timing
real 1m10.555s user 6m12.164s sys 0m18.262s

Method

The timing script used can be viewed at run.sh.

In it we compile two debug builds, the first with rust-cssparser enabled and the second with lightningcss enabled.

The code used is copied below for convenience.

# via: ./Cargo.toml

[package]
name = "rust-cssparser-and-lightningcss-compile-times"
version = "0.1.0"
edition = "2021"

[features]
with-lightningcss = ["lightningcss"]
with-rust-cssparser = ["cssparser"]

[dependencies]
cssparser = {optional = true, version = "=0.29"}
lightningcss = {optional = true, version = "=1.0.0-alpha.38"}

// via: ./src/main.rs

fn main() {
    #[cfg(feature = "with-rust-cssparser")]
    run_cssparser();
    #[cfg(feature = "with-lightningcss")]
    run_lightningcss();
}

#[cfg(feature = "with-rust-cssparser")]
fn run_cssparser() {
    use cssparser::{Parser, ParserInput};

    let mut input = ParserInput::new("body { color: red; }");
    let mut parser = Parser::new(&mut input);

    for token in parser.next() {
        dbg!(&token);
    }
}

#[cfg(feature = "with-lightningcss")]
fn run_lightningcss() {
    use lightningcss::stylesheet::{ParserOptions, PrinterOptions, StyleSheet};
    let sheet = StyleSheet::parse("body { color: red; }", ParserOptions::default()).unwrap();
    println!("{}", sheet.to_css(PrinterOptions::default()).unwrap().code);
}

# via: ./run.sh

#!/bin/bash

set -e

cargo clean

exec 3>&1 4>&2
RUST_CSS_PARSER_TIME=$( { time cargo build --release --features with-rust-cssparser 1>&3 2>&4; } 2>&1 )
exec 3>&- 4>&-

cargo clean

exec 3>&1 4>&2
LIGHTNINGCSS_PARSER_TIME=$( { time cargo build --release --features with-lightningcss 1>&3 2>&4; } 2>&1 )
exec 3>&- 4>&-

echo "rust-cssparser debug build timing"
echo $RUST_CSS_PARSER_TIME

echo ""

echo "lightningcss debug build timing"
echo $LIGHTNINGCSS_PARSER_TIME