Refactor Gemfile.loader to use instance_eval for proper __dir__ resolution

Changed eval() to instance_eval(content, filepath) which preserves __dir__
in evaluated content (matching Bundler's internal eval_gemfile pattern).

This allows eval_gemfile calls to work correctly inside loaded files,
so shared dev dependencies can now be loaded from Gemfile.development_dependencies
where they logically belong, instead of requiring a workaround in the main Gemfile.

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

Co-Authored-By: Claude Opus 4.5 <[email protected]>

Author: ihabadham

react_on_rails_pro/Gemfile

@@ -5,8 +5,4 @@ source "https://rubygems.org"
 # Specify your gem"s dependencies in react_on_rails.gemspec
 gemspec
 
-# Shared dev dependencies must be loaded here (not in Gemfile.development_dependencies)
-# because Gemfile.loader uses eval() which breaks __dir__ resolution
-eval_gemfile File.expand_path("../Gemfile.shared_dev_dependencies", __dir__)
-
 eval_gemfile File.expand_path("./Gemfile.loader", __dir__)

react_on_rails_pro/Gemfile.development_dependencies

@@ -1,9 +1,8 @@
 # Keep in sync with https://github.com/shakacode/react_on_rails/blob/master/Gemfile.development_dependencies
 # frozen_string_literal: true
 
-# NOTE: Shared dev dependencies (rubocop, etc.) are loaded via eval_gemfile in
-# the main Gemfile, not here. This is because Gemfile.loader uses eval() which
-# breaks __dir__ resolution for eval_gemfile calls.
+# Shared dev dependencies (rubocop, etc.)
+eval_gemfile File.expand_path("../Gemfile.shared_dev_dependencies", __dir__)
 
 git_source(:github) { |repo| "https://github.com/#{repo}.git" }
 

react_on_rails_pro/Gemfile.loader

@@ -1,19 +1,20 @@
 # frozen_string_literal: true
 
 # Load base dependencies
-base_deps = File.read(File.expand_path("./Gemfile.development_dependencies", __dir__))
+base_deps_path = File.expand_path("./Gemfile.development_dependencies", __dir__)
+base_deps = File.read(base_deps_path)
 
 # Determine which override file to use
-override_deps = if ENV["CI"] == "true" && File.exist?(File.expand_path("./Gemfile.ci", __dir__))
+override_deps_path = if ENV["CI"] == "true" && File.exist?(File.expand_path("./Gemfile.ci", __dir__))
   # In CI environment, use CI dependencies
-  File.read(File.expand_path("./Gemfile.ci", __dir__))
+  File.expand_path("./Gemfile.ci", __dir__)
 elsif File.exist?(File.expand_path("./Gemfile.local", __dir__))
   # In non-CI environment, use local dependencies if they exist
-  File.read(File.expand_path("./Gemfile.local", __dir__))
-else
-  ""
+  File.expand_path("./Gemfile.local", __dir__)
 end
 
+override_deps = override_deps_path ? File.read(override_deps_path) : ""
+
 # Parse override gems
 override_gem_names = override_deps.scan(/^\s*gem\s+["']([^"']+)["']/).flatten
 
@@ -26,7 +27,9 @@ end
 base_deps.gsub!(/^\s*$\n/, '')
 
 # Evaluate the modified base dependencies
-eval(base_deps)
+# Using instance_eval with filepath preserves __dir__ in evaluated content,
+# allowing eval_gemfile calls to work correctly inside loaded files.
+instance_eval(base_deps, base_deps_path)
 
 # Evaluate override dependencies if they exist
-eval(override_deps) unless override_deps.empty?
+instance_eval(override_deps, override_deps_path) unless override_deps.empty?