Parser: Parse CSS and <style> tags using Lightning CSS

Author: marcoroth

.clang-format-ignore

@@ -5,5 +5,6 @@ src/ast_pretty_print.c
 src/errors.c
 src/include/ast_nodes.h
 src/include/ast_pretty_print.h
+src/include/css_parser.h
 src/include/errors.h
 src/visitor.c

.github/workflows/build-gems.yml

@@ -75,6 +75,14 @@ jobs:
         with:
           bundler-cache: false
 
+      - name: Set up Rust
+        uses: dtolnay/rust-toolchain@stable
+        with:
+          toolchain: stable
+
+      - name: Build CSS Parser
+        run: cd src/css && cargo build --release
+
       - name: bundle install
         run: bundle install
 

.github/workflows/build.yml

@@ -34,12 +34,26 @@ jobs:
         with:
           bundler-cache: true
 
+      - name: Set up Rust
+        uses: dtolnay/rust-toolchain@stable
+        with:
+          toolchain: stable
+
+      - name: Install Rust WASM target
+        run: rustup target add wasm32-unknown-emscripten
+
+      - name: Build CSS Parser
+        run: cd src/css && cargo build --release
+
       - name: bundle install
         run: bundle install
 
       - name: Render Templates
         run: bundle exec rake templates
 
+      - name: make all
+        run: make all
+
       - name: Compile Herb
         run: bundle exec rake make
 

.github/workflows/deploy.yml

@@ -53,6 +53,17 @@ jobs:
         with:
           bundler-cache: true
 
+      - name: Set up Rust
+        uses: dtolnay/rust-toolchain@stable
+        with:
+          toolchain: stable
+
+      - name: Install Rust WASM target
+        run: rustup target add wasm32-unknown-emscripten
+
+      - name: Build CSS Parser
+        run: cd src/css && cargo build --release
+
       - name: bundle install
         run: bundle install
 

.github/workflows/javascript.yml

@@ -41,6 +41,17 @@ jobs:
         with:
           bundler-cache: true
 
+      - name: Set up Rust
+        uses: dtolnay/rust-toolchain@stable
+        with:
+          toolchain: stable
+
+      - name: Install Rust WASM target
+        run: rustup target add wasm32-unknown-emscripten
+
+      - name: Build CSS Parser
+        run: cd src/css && cargo build --release
+
       - name: bundle install
         run: bundle install
 

.gitignore

@@ -134,3 +134,7 @@ docs/docs/public/c-reference
 
 # NPM
 **/node_modules/**/*
+
+# Rust (CSS Parser)
+src/css/target/
+src/include/css_parser.h

Makefile

@@ -37,6 +37,10 @@ prism_build = $(prism_path)/build
 prism_flags = -I$(prism_include)
 prism_ldflags = $(prism_build)/libprism.a
 
+css_parser_dir = src/css
+css_parser_lib = $(css_parser_dir)/target/release/libherb_css_parser.a
+css_parser_flags = -I$(css_parser_dir)
+
 # Enable strict warnings
 warning_flags = -Wall -Wextra -Werror -pedantic
 
@@ -50,42 +54,44 @@ production_flags = $(warning_flags) -O3 -march=native -flto
 shared_library_flags = -fPIC
 
 # Default build mode (change this as needed)
-flags = $(warning_flags) $(debug_flags) $(prism_flags) -std=c99
+flags = $(warning_flags) $(debug_flags) $(prism_flags) $(css_parser_flags) -std=c99
 
 # Separate test compilation flags
-test_flags = $(debug_flags) $(prism_flags) -std=gnu99
+test_flags = $(debug_flags) $(prism_flags) $(css_parser_flags) -std=gnu99
 
 # Shared library build (if needed)
-shared_flags = $(production_flags) $(shared_library_flags) $(prism_flags)
+shared_flags = $(production_flags) $(shared_library_flags) $(prism_flags) $(css_parser_flags)
 
 ifeq ($(os),Linux)
+  css_parser_ldflags = $(css_parser_lib) -ldl -lpthread -lm
   test_cflags = $(test_flags) -I/usr/include/check
-  test_ldflags = -L/usr/lib/x86_64-linux-gnu -lcheck -lm -lsubunit $(prism_ldflags)
+  test_ldflags = -L/usr/lib/x86_64-linux-gnu -lcheck -lm -lsubunit $(prism_ldflags) $(css_parser_ldflags)
   cc = clang-21
   clang_format = clang-format-21
   clang_tidy = clang-tidy-21
 endif
 
 ifeq ($(os),Darwin)
+  css_parser_ldflags = $(css_parser_lib) -lresolv -framework Security -framework CoreFoundation
   brew_prefix := $(shell brew --prefix check)
   test_cflags = $(test_flags) -I$(brew_prefix)/include
-  test_ldflags = -L$(brew_prefix)/lib -lcheck -lm $(prism_ldflags)
+  test_ldflags = -L$(brew_prefix)/lib -lcheck -lm $(prism_ldflags) $(css_parser_ldflags)
   llvm_path = $(shell brew --prefix llvm@21)
   cc = $(llvm_path)/bin/clang
   clang_format = $(llvm_path)/bin/clang-format
   clang_tidy = $(llvm_path)/bin/clang-tidy
 endif
 
-all: templates prism $(exec) $(lib_name) $(static_lib_name) test wasm
+all: templates prism css_parser $(exec) $(lib_name) $(static_lib_name) test wasm
 
-$(exec): $(objects)
-	$(cc) $(objects) $(flags) $(ldflags) $(prism_ldflags) -o $(exec)
+$(exec): $(objects) $(css_parser_lib)
+	$(cc) $(objects) $(flags) $(ldflags) $(prism_ldflags) $(css_parser_ldflags) -o $(exec)
 
-$(lib_name): $(objects)
-	$(cc) -shared $(objects) $(shared_flags) $(ldflags) $(prism_ldflags) -o $(lib_name)
+$(lib_name): $(objects) $(css_parser_lib)
+	$(cc) -shared $(objects) $(shared_flags) $(ldflags) $(prism_ldflags) $(css_parser_ldflags) -o $(lib_name)
 	# cp $(lib_name) $(ruby_extension)
 
-$(static_lib_name): $(objects)
+$(static_lib_name): $(objects) $(css_parser_lib)
 	ar rcs $(static_lib_name) $(objects)
 
 src/%.o: src/%.c templates
@@ -102,6 +108,7 @@ clean:
 	rm -rf $(objects) $(test_objects) $(extension_objects) lib/herb/*.bundle tmp
 	rm -rf $(prism_path)
 	rake prism:clean
+	cd $(css_parser_dir) && cargo clean
 
 bundle_install:
 	bundle install
@@ -113,6 +120,12 @@ prism: bundle_install
 	cd $(prism_path) && ruby templates/template.rb && make static && cd -
 	rake prism:vendor
 
+css_parser: $(css_parser_lib)
+
+$(css_parser_lib):
+	cd $(css_parser_dir) && cargo build --release
+	cbindgen --config $(css_parser_dir)/cbindgen.toml --output src/include/css_parser.h $(css_parser_dir)
+
 format:
 	$(clang_format) -i $(project_and_extension_files)
 

config.yml

@@ -712,3 +712,35 @@ nodes:
         - name: statements
           type: array
           kind: Node
+
+    - name: CSSDeclarationNode
+      fields:
+        - name: property
+          type: string
+
+        - name: value
+          type: string
+
+    - name: CSSRuleNode
+      fields:
+        - name: selector
+          type: string
+
+        - name: declarations
+          type: array
+          kind: CSSDeclarationNode
+
+    - name: CSSStyleNode
+      fields:
+        - name: content
+          type: string
+
+        - name: rules
+          type: array
+          kind: CSSRuleNode
+
+        - name: valid
+          type: boolean
+
+        - name: parse_error
+          type: string

ext/herb/extconf.rb

@@ -10,10 +10,13 @@
 
 include_path = File.expand_path("../../src/include", __dir__)
 prism_path = File.expand_path("../../vendor/prism", __dir__)
+css_parser_path = File.expand_path("../../src/css", __dir__)
 
 prism_src_path = "#{prism_path}/src"
 prism_include_path = "#{prism_path}/include"
 
+css_parser_lib = "#{css_parser_path}/target/release/libherb_css_parser.a"
+
 $VPATH << "$(srcdir)/../../src"
 $VPATH << "$(srcdir)/../../src/util"
 $VPATH << prism_src_path
@@ -23,9 +26,17 @@
 $INCFLAGS << " -I#{include_path}"
 $INCFLAGS << " -I#{prism_src_path}"
 $INCFLAGS << " -I#{prism_src_path}/util"
+$INCFLAGS << " -I#{css_parser_path}"
 
 $CFLAGS << " -DPRISM_EXPORT_SYMBOLS=static "
 
+$LDFLAGS << " #{css_parser_lib}"
+if RUBY_PLATFORM.match?(/darwin/)
+  $LDFLAGS << " -lresolv -framework Security -framework CoreFoundation"
+elsif RUBY_PLATFORM.match?(/linux/)
+  $LDFLAGS << " -ldl -lpthread -lm"
+end
+
 herb_src_files = Dir.glob("#{$srcdir}/../../src/**/*.c").map { |file| file.delete_prefix("../../../../ext/herb/") }.sort
 
 prism_main_files = %w[

javascript/packages/formatter/src/format-printer.ts

@@ -91,6 +91,9 @@ import {
   ERBInNode,
   XMLDeclarationNode,
   CDATANode,
+  CSSStyleNode,
+  CSSRuleNode,
+  CSSDeclarationNode,
   Token
 } from "@herb-tools/core"
 
@@ -1192,6 +1195,20 @@ export class FormatPrinter extends Printer {
     if (node.end_node) this.visit(node.end_node)
   }
 
+  visitCSSStyleNode(node: CSSStyleNode) {
+    if (node.content) {
+      this.push(node.content)
+    }
+  }
+
+  visitCSSRuleNode(_node: CSSRuleNode) {
+    // CSS rules are contained within CSSStyleNode, not rendered separately
+  }
+
+  visitCSSDeclarationNode(_node: CSSDeclarationNode) {
+    // CSS declarations are contained within CSSRuleNode, not rendered separately
+  }
+
   // --- Element Formatting Analysis Helpers ---
 
   /**