bench: add tailwind_parse benchmark to isolate parser from merge pipeline

Exposes parse_tailwind, AstStyle, and AstParseOptions via a #[doc(hidden)]
__bench module so the nom parser can be benchmarked independently of
conflict detection and class merging.

Author: max-wells

crates/tw_merge/tw_merge/benches/merge.rs

@@ -1,4 +1,5 @@
 use divan::Bencher;
+use tw_merge::__bench::{AstParseOptions, parse_tailwind};
 use tw_merge::merge::{merge_classes, tw_merge_slice};
 
 fn main() {
@@ -27,6 +28,15 @@ fn tailwind_merge_slice(bencher: Bencher, len: usize) {
     bencher.with_inputs(|| generate_random_classes(len)).bench_values(|class| tw_merge_slice(&class));
 }
 
+#[divan::bench(
+    args = LENS,
+    sample_count = SAMPLE_COUNT,
+    sample_size = SAMPLE_SIZE
+)]
+fn tailwind_parse(bencher: Bencher, len: usize) {
+    bencher.with_inputs(|| generate_random_classes(len)).bench_values(|classes| parse_tailwind(&classes, AstParseOptions::default()));
+}
+
 // create a vec with the a length of len and fill it with random data
 fn generate_random_classes(n: usize) -> Vec<&'static str> {
     let mut classes_vec = Vec::with_capacity(n);

crates/tw_merge/tw_merge/src/ast/mod.rs

@@ -2,10 +2,13 @@ mod parser;
 #[cfg(test)]
 mod parser_test;
 
-pub(crate) use parser::{parse_tailwind, take_until_unbalanced};
+pub(crate) use parser::take_until_unbalanced;
+#[doc(hidden)]
+pub use parser::parse_tailwind;
 
+#[doc(hidden)]
 #[derive(Clone, Debug, PartialEq, Default)]
-pub(crate) struct AstStyle<'a> {
+pub struct AstStyle<'a> {
     pub source: &'a str,
     /// Is a `!important` style
     pub important: bool,
@@ -36,8 +39,9 @@ enum ASTVariant<'a> {
     ArbitraryAttribute(&'a str),
 }
 
+#[doc(hidden)]
 #[derive(Clone, Debug, PartialEq)]
-pub(crate) struct AstParseOptions<'a> {
+pub struct AstParseOptions<'a> {
     /// Custom prefix for modifiers in Tailwind classes
     /// <https://tailwindcss.com/docs/configuration#prefix>
     pub prefix: &'a str,
@@ -46,6 +50,7 @@ pub(crate) struct AstParseOptions<'a> {
     pub separator: &'a str,
 }
 
+#[doc(hidden)]
 impl Default for AstParseOptions<'static> {
     fn default() -> Self {
         Self { prefix: "", separator: ":" }

crates/tw_merge/tw_merge/src/ast/parser.rs

@@ -8,6 +8,8 @@ use nom::sequence::{delimited, tuple};
 
 use super::{ASTVariant, AstElements, AstParseOptions, AstStyle};
 
+/// Parses a slice of Tailwind class strings into structured AST nodes.
+#[doc(hidden)]
 pub fn parse_tailwind<'a>(class: &[&'a str], options: AstParseOptions<'a>) -> Vec<Result<AstStyle<'a>, &'a str>> {
     class
         .iter()

crates/tw_merge/tw_merge/src/lib.rs

@@ -262,6 +262,17 @@ pub use crate::core::{merge, *};
 mod ast;
 mod core;
 
+/// Internal utilities exposed for benchmarking only. Not part of the public API.
+#[doc(hidden)]
+pub mod __bench {
+    #[doc(hidden)]
+    pub use crate::ast::AstParseOptions;
+    #[doc(hidden)]
+    pub use crate::ast::AstStyle;
+    #[doc(hidden)]
+    pub use crate::ast::parse_tailwind;
+}
+
 #[cfg(feature = "variant")]
 pub use variant::*;