perf: Replace better_html dependency with herb

Gemfile.lock

@@ -5,9 +5,9 @@ PATH
       activesupport (>= 6.0)
       ast
       benchmark
-      better_html
       bundler
       constant_resolver (>= 0.3)
+      herb
       parallel (< 2)
       parser
       prism (>= 1.4.0)
@@ -50,13 +50,6 @@ GEM
     ast (2.4.3)
     base64 (0.3.0)
     benchmark (0.5.0)
-    better_html (2.1.1)
-      actionview (>= 6.0)
-      activesupport (>= 6.0)
-      ast (~> 2.0)
-      erubi (~> 1.4)
-      parser (>= 2.4)
-      smart_properties
     bigdecimal (4.1.2)
     builder (3.3.0)
     byebug (11.1.3)
@@ -70,6 +63,10 @@ GEM
     erb (4.0.4.1)
       cgi (>= 0.3.3)
     erubi (1.13.1)
+    herb (0.10.1-aarch64-linux-gnu)
+    herb (0.10.1-arm64-darwin)
+    herb (0.10.1-x86_64-darwin)
+    herb (0.10.1-x86_64-linux-gnu)
     i18n (1.14.8)
       concurrent-ruby (~> 1.0)
     io-console (0.8.0)
@@ -185,7 +182,6 @@ GEM
     rubydex (0.2.0-x86_64-darwin)
     rubydex (0.2.0-x86_64-linux)
     securerandom (0.4.1)
-    smart_properties (1.17.0)
     sorbet (0.6.13184)
       sorbet-static (= 0.6.13184)
     sorbet-runtime (0.6.13184)

lib/packwerk/parsers/erb.rb

@@ -1,19 +1,16 @@
 # typed: strict
 # frozen_string_literal: true
 
-require "ast/node"
-require "better_html"
-require "better_html/parser"
+require "herb"
 require "parser/source/buffer"
 
 module Packwerk
   module Parsers
     class Erb
       include ParserInterface
 
-      #: (?parser_class: untyped, ?ruby_parser: Ruby) -> void
-      def initialize(parser_class: BetterHtml::Parser, ruby_parser: Ruby.new)
-        @parser_class = parser_class #: singleton(BetterHtml::Parser)
+      #: (?ruby_parser: Ruby) -> void
+      def initialize(ruby_parser: Ruby.new)
         @ruby_parser = ruby_parser
       end
 
@@ -25,53 +22,16 @@ def call(io:, file_path: "<unknown>")
         parse_buffer(buffer, file_path: file_path)
       end
 
+      # `Herb.extract_ruby` returns the Ruby parts of the ERB source with whitespace padding
+      # so character positions match the original file — that gives Packwerk's downstream
+      # reference offenses accurate line/column info in ERB templates.
       #: (Parser::Source::Buffer buffer, file_path: String) -> AST::Node?
       def parse_buffer(buffer, file_path:)
-        parser = @parser_class.new(buffer, template_language: :html)
-        to_ruby_ast(parser.ast, file_path)
+        ruby_source = Herb.extract_ruby(buffer.source)
+        @ruby_parser.call(io: StringIO.new(ruby_source), file_path: file_path)
       rescue EncodingError => e
         result = ParseResult.new(file: file_path, message: e.message)
         raise Parsers::ParseError, result
-      rescue Parser::SyntaxError => e
-        result = ParseResult.new(file: file_path, message: "Syntax error: #{e}")
-        raise Parsers::ParseError, result
-      end
-
-      private
-
-      #: ((::AST::Node & Object) erb_ast, String file_path) -> ::AST::Node?
-      def to_ruby_ast(erb_ast, file_path)
-        # Note that we're not using the source location (line/column) at the moment, but if we did
-        # care about that, we'd need to tweak this to insert empty lines and spaces so that things
-        # line up with the ERB file
-        nodes = code_nodes(erb_ast) #: as !nil
-        code_pieces = nodes.map do |node|
-          node #: as ::AST::Node
-            .children.first
-        end
-
-        @ruby_parser.call(
-          io: StringIO.new(code_pieces.join("\n")),
-          file_path: file_path,
-        )
-      end
-
-      #: ((::AST::Node | String)? node) ?{ (::AST::Node arg0) -> void } -> (Enumerator[::AST::Node] | Array[String])?
-      def code_nodes(node, &block)
-        return enum_for(:code_nodes, node) unless block
-        return unless node.is_a?(::AST::Node)
-
-        yield node if node.type == :code
-
-        # Skip descending into an ERB comment node, which may contain code nodes
-        if node.type == :erb
-          first_child = node.children.first
-          return if first_child&.type == :indicator && first_child&.children&.first == "#"
-        end
-
-        node.children.each do |child|
-          code_nodes(child, &block)
-        end
       end
     end
   end

packwerk.gemspec

@@ -51,5 +51,5 @@ Gem::Specification.new do |spec|
   spec.add_dependency("prism", ">= 1.4.0")
 
   # For ERB parsing
-  spec.add_dependency("better_html")
+  spec.add_dependency("herb")
 end