fix: Address code review issues in JS dependency manager

- Restore version validation for pre-release versions in add_react_on_rails_package
- Clarify TypeScript dependencies comment for SWC-first approach
- Add explanatory comment about package_json availability
- Fix test mocks to match actual implementation using add_npm_dependencies
- Remove stale react-on-rails@^16.1.0 entry from yarn.lock

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

Co-Authored-By: Claude <noreply@anthropic.com>

Author: justin808

lib/generators/react_on_rails/js_dependency_manager.rb

@@ -78,9 +78,10 @@ module JsDependencyManager
 
       # TypeScript dependencies (only installed when --typescript flag is used)
       # Note: @babel/preset-typescript is NOT included because:
-      # - SWC (the default) has built-in TypeScript support
-      # - Shakapacker handles the loader configuration
-      # - For Babel users, they can add @babel/preset-typescript manually if needed
+      # - SWC is now the default webpack_loader (has built-in TypeScript support)
+      # - Shakapacker handles the loader configuration via shakapacker.yml
+      # - If users choose webpack_loader: 'babel', they should manually add @babel/preset-typescript
+      #   and configure it in their babel.config.js
       TYPESCRIPT_DEPENDENCIES = %w[
         typescript
         @types/react
@@ -114,8 +115,17 @@ def add_js_dependencies
       end
 
       def add_react_on_rails_package
-        # Always use exact version match between gem and npm package
-        react_on_rails_pkg = "react-on-rails@#{ReactOnRails::VERSION}"
+        # Use exact version match between gem and npm package for stable releases
+        # For pre-release versions (e.g., 16.1.0-rc.1), use latest to avoid installing
+        # a version that may not exist in the npm registry
+        major_minor_patch_only = /\A\d+\.\d+\.\d+\z/
+        react_on_rails_pkg = if ReactOnRails::VERSION.match?(major_minor_patch_only)
+                               "react-on-rails@#{ReactOnRails::VERSION}"
+                             else
+                               puts "Adding the latest react-on-rails NPM module. " \
+                                    "Double check this is correct in package.json"
+                               "react-on-rails"
+                             end
 
         puts "Installing React on Rails package..."
         if add_js_dependency(react_on_rails_pkg)
@@ -237,6 +247,10 @@ def add_js_dependencies_batch(packages, dev: false)
 
       def install_js_dependencies
         # Use package_json gem's install method (always available via shakapacker)
+        # package_json is guaranteed to be available because:
+        # 1. react_on_rails gemspec requires shakapacker
+        # 2. shakapacker gemspec requires package_json
+        # 3. GeneratorHelper provides package_json method
         package_json.manager.install
         true
       rescue StandardError => e

spec/react_on_rails/generators/message_deduplication_spec.rb

@@ -83,9 +83,17 @@
 
     context "when using package_json gem (always available via shakapacker)" do
       before do
-        # Mock that the package_json gem methods succeed
-        allow(install_generator).to receive_messages(add_js_dependency: true, add_js_dependencies_batch: true,
-                                                     install_js_dependencies: true)
+        # Mock the actual methods used by JsDependencyManager
+        # add_npm_dependencies is from GeneratorHelper and is used by add_js_dependencies_batch
+        # Mock package_json to prevent actual package manager calls
+        # rubocop:disable RSpec/VerifiedDoubles
+        mock_manager = double("PackageManager", install: true)
+        mock_package_json = double("PackageJson", manager: mock_manager)
+        # rubocop:enable RSpec/VerifiedDoubles
+        allow(install_generator).to receive_messages(
+          add_npm_dependencies: true,
+          package_json: mock_package_json
+        )
       end
 
       it "does not run duplicate install commands" do

yarn.lock

@@ -5364,11 +5364,6 @@ react-on-rails-rsc@19.0.2:
     neo-async "^2.6.1"
     webpack-sources "^3.2.0"
 
-react-on-rails@^16.1.0:
-  version "16.1.0"
-  resolved "https://registry.yarnpkg.com/react-on-rails/-/react-on-rails-16.1.0.tgz#1d6a91edf6c5675f22f4449483b604690471a76e"
-  integrity sha512-EZbs868+V6gkxY52jeim64oETHSg6ztym5aL9FFBY5uEadb/FaAAoCNrutyObFR/XgzGqmeSKQdW1DvPl8BVyA==
-
 react@^19.0.0:
   version "19.0.0"
   resolved "https://registry.npmjs.org/react/-/react-19.0.0.tgz"