Fix false positive in async detection for mixed commented/uncommented tags

Critical bug fix: The content_has_only_commented_async? method was
incorrectly flagging files that had:
- Uncommented javascript_pack_tag WITHOUT :async
- Commented javascript_pack_tag WITH :async

The previous implementation checked if ANY uncommented javascript_pack_tag
existed, not specifically ones with :async. This caused false positives.

Solution: Refactored to remove all commented lines first, then check if
:async exists in the remaining content. This handles both single-line
and multi-line tags correctly and is more robust.

Added comprehensive test case to prevent regression.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <[email protected]>

Author: justin808

lib/react_on_rails/doctor.rb

@@ -1226,29 +1226,21 @@ def file_has_async_pack_tag?(content)
     def content_has_only_commented_async?(content)
       # Check if all occurrences of javascript_pack_tag with :async are in comments
       # Returns true if ONLY commented async usage exists (no active async usage)
-      # Note: We need to check the full content first (for multi-line tags) before line-by-line filtering
 
       # First check if there's any javascript_pack_tag with :async in the full content
       return true unless file_has_async_pack_tag?(content)
 
-      # Now check line-by-line to see if all occurrences are commented
-      # For multi-line tags, we check if the starting line is commented
-      has_uncommented_async = content.each_line.any? do |line|
-        # Skip lines that don't contain javascript_pack_tag
-        next unless line.include?("javascript_pack_tag")
-
-        # Skip ERB comments (<%# ... %>)
-        next if line.match?(ERB_COMMENT_PATTERN)
-        # Skip HAML comments (-# ...)
-        next if line.match?(HAML_COMMENT_PATTERN)
-        # Skip HTML comments (<!-- ... -->)
-        next if line.match?(HTML_COMMENT_PATTERN)
-
-        # If we reach here, this line has an uncommented javascript_pack_tag
-        true
+      # Strategy: Remove all commented lines, then check if any :async remains
+      # This handles both single-line and multi-line tags correctly
+      uncommented_lines = content.each_line.reject do |line|
+        line.match?(ERB_COMMENT_PATTERN) ||
+          line.match?(HAML_COMMENT_PATTERN) ||
+          line.match?(HTML_COMMENT_PATTERN)
       end
 
-      !has_uncommented_async
+      uncommented_content = uncommented_lines.join
+      # If no async found in uncommented content, all async usage was commented
+      !file_has_async_pack_tag?(uncommented_content)
     end
 
     def config_has_async_loading_strategy?

spec/lib/react_on_rails/doctor_spec.rb

@@ -342,6 +342,23 @@
       end
     end
 
+    context "when file has uncommented pack tag without :async and commented one with :async" do
+      before do
+        allow(Dir).to receive(:glob).with("app/views/**/*.erb")
+                                    .and_return(["app/views/layouts/application.html.erb"])
+        allow(Dir).to receive(:glob).with("app/views/**/*.haml").and_return([])
+        allow(File).to receive(:exist?).with("app/views/layouts/application.html.erb").and_return(true)
+        allow(File).to receive(:read).with("app/views/layouts/application.html.erb")
+                                     .and_return('<%= javascript_pack_tag "app", defer: true %>
+<%# javascript_pack_tag "other", :async %>')
+      end
+
+      it "does not return files (only commented line has :async)" do
+        files = doctor.send(:scan_view_files_for_async_pack_tag)
+        expect(files).to be_empty
+      end
+    end
+
     context "when async is only in ERB comments" do
       before do
         allow(Dir).to receive(:glob).with("app/views/**/*.erb")