Using syntect as a higlighting backend rather than highlight.js

.gitignore

@@ -13,6 +13,8 @@ test_book/book/
 # Ignore Jetbrains specific files.
 .idea/
 
+src/theme/syntaxes.bin
+
 # Ignore Vim temporary and swap files.
 *.sw?
 *~

Cargo.toml

@@ -15,6 +15,20 @@ readme = "README.md"
 repository = "https://github.com/rust-lang/mdBook"
 description = "Creates a book from markdown files"
 rust-version = "1.74"
+build = "build.rs"
+
+[build-dependencies.syntect]
+version = "5.1.0"
+default-features = false
+features = [
+    # regex-onig, the default, isn't portable enough
+    "regex-fancy",
+    #"parsing",
+    "default-syntaxes",
+    "yaml-load",
+    "dump-load",
+    "dump-create",
+]
 
 [dependencies]
 anyhow = "1.0.71"
@@ -52,6 +66,21 @@ warp = { version = "0.3.6", default-features = false, features = ["websocket"],
 elasticlunr-rs = { version = "3.0.2", optional = true }
 ammonia = { version = "4.0.0", optional = true }
 
+[dependencies.syntect]
+version = "5.1.0"
+default-features = false
+features = [
+    # regex-onig, the default, isn't portable enough
+    "regex-fancy",
+    "parsing",
+    "html",
+    "default-themes",
+    "plist-load",
+    "yaml-load",
+    "dump-load",
+    "dump-create",
+]
+
 [dev-dependencies]
 assert_cmd = "2.0.11"
 predicates = "3.0.3"
@@ -61,10 +90,11 @@ pretty_assertions = "1.3.0"
 walkdir = "2.3.3"
 
 [features]
-default = ["watch", "serve", "search"]
+default = ["watch", "serve", "search", "gen-syntax-cache"]
 watch = ["dep:notify", "dep:notify-debouncer-mini", "dep:ignore", "dep:pathdiff", "dep:walkdir"]
 serve = ["dep:futures-util", "dep:tokio", "dep:warp"]
 search = ["dep:elasticlunr-rs", "dep:ammonia"]
+gen-syntax-cache = ["syntect/dump-create"]
 
 [[bin]]
 doc = false
@@ -73,3 +103,7 @@ name = "mdbook"
 [[example]]
 name = "nop-preprocessor"
 test = true
+
+[profile.dev]
+opt-level = 1
+

build.rs

@@ -0,0 +1,18 @@
+use std::env;
+use std::error::Error;
+use syntect::dumps::dump_to_file;
+use syntect::parsing::SyntaxSet;
+
+pub fn main() -> Result<(), Box<dyn Error>> {
+    let src_dir = format!(
+        "{}/src/theme/syntaxes/",
+        env::var("CARGO_MANIFEST_DIR").unwrap()
+    );
+    let dest = format!("{}/syntaxes.bin", env::var("OUT_DIR").unwrap());
+
+    let mut builder = SyntaxSet::load_defaults_newlines().into_builder();
+    builder.add_from_folder(&src_dir, true)?;
+    dump_to_file(&builder.build(), dest)?;
+
+    Ok(())
+}