Engine: Introduce SlotVisitor for slot markers

lib/herb/cli.rb

@@ -8,7 +8,7 @@
 class Herb::CLI
   include Herb::Colors
 
-  attr_accessor :json, :silent, :log_file, :no_timing, :local, :escape, :no_escape, :freeze, :debug, :tool, :strict, :analyze, :track_whitespace, :verbose, :isolate, :arena_stats, :leak_check, :action_view_helpers, :trim, :optimize, :file_timeout
+  attr_accessor :json, :silent, :log_file, :no_timing, :local, :escape, :no_escape, :freeze, :debug, :tool, :strict, :analyze, :track_whitespace, :verbose, :isolate, :arena_stats, :leak_check, :action_view_helpers, :trim, :optimize, :slots, :file_timeout
 
   def initialize(args)
     @args = args
@@ -334,6 +334,10 @@ def option_parser
         self.optimize = true
       end
 
+      parser.on("--slots", "Emit slot markers for reactive rendering (for compile/render commands) (default: false)") do
+        self.slots = true
+      end
+
       parser.on("--tool TOOL", "Show config for specific tool: linter, formatter (for config command)") do |t|
         self.tool = t.to_sym
       end
@@ -688,9 +692,12 @@ def compile_template
 
       options[:optimize] = true if optimize
       options[:trim] = true if trim
+      options[:slots] = true if slots
       options[:validate_ruby] = true
       engine = Herb::Engine.new(file_content, options)
 
+      print_warnings(engine.slot_visitor&.warnings || []) unless json
+
       if json
         result = {
           success: true,
@@ -760,6 +767,21 @@ def compile_template
     end
   end
 
+  def print_warnings(warnings)
+    return if warnings.empty?
+
+    $stderr.puts
+
+    warnings.each do |warning|
+      location = [@file, warning.location&.start&.line, warning.location&.start&.column].compact.join(":")
+
+      warn "#{bold(yellow("warning"))}: #{warning.message}"
+      warn "  #{dimmed(location)}"
+      warn "  #{dimmed(warning.expression.to_s)}" if warning.respond_to?(:expression) && warning.expression
+      $stderr.puts
+    end
+  end
+
   def render_template
     require_relative "engine"
 

lib/herb/engine.rb

@@ -6,6 +6,7 @@
 require "pathname"
 
 require_relative "engine/debug_visitor"
+require_relative "engine/slot_visitor"
 require_relative "engine/compiler"
 require_relative "engine/error_formatter"
 require_relative "engine/validation_errors"
@@ -18,8 +19,7 @@
 
 module Herb
   class Engine
-    attr_reader :src, :filename, :project_path, :relative_file_path, :bufvar, :debug, :content_for_head,
-                :validation_error_template, :visitors, :enabled_validators
+    attr_reader :src, :filename, :project_path, :relative_file_path, :bufvar, :debug, :content_for_head, :validation_error_template, :visitors, :enabled_validators, :slot_visitor
 
     # @rbs!
     #   def self.optimize_warning_issued: () -> bool
@@ -76,6 +76,7 @@ def initialize(input, properties = {})
       @chain_appends = properties[:chain_appends]
       @buffer_on_stack = false
       @debug = properties.fetch(:debug, Herb.configuration.engine_option("debug", false))
+      @slots = properties.fetch(:slots, Herb.configuration.engine_option("slots", false))
       @content_for_head = properties[:content_for_head]
       @validation_error_template = nil
       @validation_mode = properties.fetch(:validation_mode, :raise)
@@ -100,6 +101,17 @@ def initialize(input, properties = {})
         @visitors << debug_visitor
       end
 
+      if @slots
+        @parser_options[:iteration_nodes] = true unless @parser_options.key?(:iteration_nodes)
+
+        @slot_visitor = SlotVisitor.new(
+          file_path: @filename,
+          project_path: @project_path
+        )
+
+        @visitors = [@slot_visitor, *@visitors]
+      end
+
       unless [:raise, :overlay, :none].include?(@validation_mode)
         raise ArgumentError,
               "validation_mode must be one of :raise, :overlay, or :none, got #{@validation_mode.inspect}"

lib/herb/engine/slot_markers.rb

@@ -0,0 +1,48 @@
+# frozen_string_literal: true
+# typed: true
+
+module Herb
+  class Engine
+    class SlotMarkers
+      #: (Integer, Symbol) -> String
+      def slot_open(index, _type)
+        "<!--herb-slot:#{index}-->"
+      end
+
+      #: (Integer) -> String
+      def slot_close(index)
+        "<!--/herb-slot:#{index}-->"
+      end
+
+      #: (Integer, Integer) -> String
+      def branch(slot_index, branch_index)
+        "<!--herb-branch:#{slot_index}:#{branch_index}-->"
+      end
+
+      #: (Integer) -> String
+      def row_open_prefix(slot_index)
+        "<!--herb-row:#{slot_index}:"
+      end
+
+      #: () -> String
+      def row_open_suffix
+        "-->"
+      end
+
+      #: (Integer) -> String
+      def row_close(slot_index)
+        "<!--/herb-row:#{slot_index}-->"
+      end
+
+      #: (String, String) -> String
+      def region_open(file, version)
+        "<!--herb-region:#{file}:#{version}-->"
+      end
+
+      #: (String) -> String
+      def region_close(file)
+        "<!--/herb-region:#{file}-->"
+      end
+    end
+  end
+end