Engine: Avoid applying debug spans inside javascript_tag blocks (#953)

This pull request fixes #952.

`javascript_tag` blocks were still receiving debug spans when debug mode
was enabled, even though raw `<script>` tags were already excluded. This
caused JavaScript code inside the helper to break.

To address this, I introduced an `@erb_block_stack` to track the current
ERB block and extended `in_excluded_context?` to detect `javascript_tag`
calls within ERB. When inside such a block, debug spans are skipped.

A snapshot test has been added to ensure that ERB expressions inside
`javascript_tag` do not receive debug spans.

If you have any feedback on the approach or implementation, I’d be happy
to adjust!

Author: kozy4324

lib/herb/engine/debug_visitor.rb

@@ -25,6 +25,7 @@ def initialize(file_path: nil, project_path: nil)
         @relative_file_path = calculate_relative_path
         @top_level_elements = [] #: Array[Herb::AST::HTMLElementNode]
         @element_stack = [] #: Array[String]
+        @erb_block_stack = [] #: Array[Herb::AST::ERBBlockNode]
         @debug_attributes_applied = false
         @in_attribute = false
         @in_html_comment = false
@@ -83,6 +84,12 @@ def visit_erb_yield_node(_node)
         nil
       end
 
+      def visit_erb_block_node(node)
+        @erb_block_stack.push(node)
+        super
+        @erb_block_stack.pop
+      end
+
       private
 
       def calculate_relative_path
@@ -295,7 +302,11 @@ def in_script_or_style_context?
 
       def in_excluded_context?
         excluded_tags = ["script", "style", "head", "textarea", "pre"]
-        excluded_tags.any? { |tag| @element_stack.include?(tag) }
+        return true if excluded_tags.any? { |tag| @element_stack.include?(tag) }
+
+        return true if @erb_block_stack.any? { |node| javascript_tag?(node.content.value.strip) }
+
+        false
       end
 
       def erb_output?(opening)
@@ -332,6 +343,18 @@ def complex_rails_helper?(code)
 
         false
       end
+
+      # TODO: Rewrite using Prism Nodes once available
+      def javascript_tag?(code)
+        cleaned_code = code.strip.gsub(/\s+/, " ")
+
+        return true if cleaned_code.match?(/\bjavascript_tag\s.*do\s*$/) ||
+                       cleaned_code.match?(/\bjavascript_tag\s.*\{\s*$/) ||
+                       cleaned_code.match?(/\bjavascript_tag\(.*do\s*$/) ||
+                       cleaned_code.match?(/\bjavascript_tag\(.*\{\s*$/)
+
+        false
+      end
     end
   end
 end

sig/herb/engine/debug_visitor.rbs

@@ -391,5 +391,16 @@ class DebugModeTest < Minitest::Spec
     test "regular div content still gets debug spans after excluded context tests" do
       assert_compiled_snapshot("<div><%= @content %></div>", debug: true)
     end
+
+    test "javascript_tag content erb expressions do NOT get debug spans" do
+      template = <<~ERB
+        <%= javascript_tag do %>
+          var userId = <%= @user.id %>;
+          var name = "<%= @user.name %>";
+        <% end %>
+      ERB
+
+      assert_compiled_snapshot(template, debug: true)
+    end
   end
 end