Refactor: Extract JS dependency management into shared module (#2051)

## Summary

This PR refactors JavaScript dependency management in React on Rails
generators by extracting duplicated code into a shared
`JsDependencyManager` module.

## Changes

- **Eliminates ~270 lines of duplicated code** between `BaseGenerator`
and `InstallGenerator`
- **Centralizes dependency definitions** in frozen constants with clear
documentation
- **Removes Babel dependencies** that are now managed by Shakapacker
- **Changes default transpiler to SWC** in generated shakapacker.yml for
better performance
- **Adds comprehensive test coverage** for the new module
- **Simplifies dependency installation flow** using package_json gem

## Key Improvements

### Code Organization
- All JS dependencies are now defined as frozen constants
(REACT_DEPENDENCIES, CSS_DEPENDENCIES, etc.)
- Clear separation of concerns with well-documented module
- Consistent error handling across all generators

### Dependency Management
- Leverages package_json gem (always available via Shakapacker) for
reliable cross-platform package management
- Removes Babel-related packages that Shakapacker now handles
automatically
- Adds support for Rspack and TypeScript dependencies

### Default Configuration
- ⚠️ **Breaking Change**: Default `webpack_loader` changed from
`'babel'` to `'swc'` in generated shakapacker.yml
- SWC provides better performance and has built-in TypeScript support
- Users who need Babel can still configure it manually

## Testing

New test file
`spec/react_on_rails/generators/message_deduplication_spec.rb` verifies:
- No duplicate post-install messages
- Proper module inclusion in both generators
- Correct dependency installation flow

## Migration Notes

For new installations, this change is transparent. Existing projects are
not affected as this only impacts the generator output for new setups.

---

Supersedes and closes #2030 (that PR had merge conflict issues, so
starting fresh with a clean branch)

<!-- This is an auto-generated comment: release notes by coderabbit.ai
-->
## Summary by CodeRabbit

* **Refactor**
* Centralized JavaScript dependency management across generators for
more consistent installation and simplified generator behavior.

* **Configuration**
* Installer config adds javascript_transpiler and assets_bundler
options; previous webpack-specific key removed.

* **Tests**
* New specs for post-install messages, message deduplication, and JS
dependency flows to validate installation messaging and dependency
handling.

* **Changelog**
* Generator no longer auto-installs Babel presets; SWC is the default
transpiler and Babel must be added manually.
<!-- end of auto-generated comment: release notes by coderabbit.ai -->

---------

Co-authored-by: Claude <noreply@anthropic.com>

Author: justin808

CHANGELOG.md

@@ -57,6 +57,8 @@ Changes since the last non-beta release.
 
 - **Generator Configuration Modernization**: Updated the generator to enable recommended configurations by default for new applications. `config.build_test_command` is now uncommented and set to `"RAILS_ENV=test bin/shakapacker"` by default, enabling automatic asset building during tests for better integration test reliability. `config.auto_load_bundle = true` is now set by default, enabling automatic loading of component bundles. `config.components_subdirectory = "ror_components"` is now set by default, organizing React components in a dedicated subdirectory. **Note:** These changes only affect newly generated applications. Existing applications are unaffected and do not need to make any changes. If you want to adopt these settings in an existing app, you can manually add them to your `config/initializers/react_on_rails.rb` file. [PR 2039](https://github.com/shakacode/react_on_rails/pull/2039) by [justin808](https://github.com/justin808).
 
+- **Removed Babel Dependency Installation**: The generator no longer installs `@babel/preset-react` or `@babel/preset-typescript` packages. Shakapacker handles JavaScript transpiler configuration (Babel, SWC, or esbuild) via the `javascript_transpiler` setting in `shakapacker.yml`. SWC is now the default transpiler and includes built-in support for React and TypeScript. Users who explicitly choose Babel will need to manually install and configure the required presets. This change reduces unnecessary dependencies and aligns with Shakapacker's modular transpiler approach. [PR 2051](https://github.com/shakacode/react_on_rails/pull/2051) by [justin808](https://github.com/justin808).
+
 #### Documentation
 
 - **Simplified Configuration Files**: Improved configuration documentation and generator template for better clarity and usability. Reduced generator template from 67 to 42 lines (37% reduction). Added comprehensive testing configuration guide. Reorganized configuration docs into Essential vs Advanced sections. Enhanced Doctor program with diagnostics for server rendering and test compilation consistency. [PR #2011](https://github.com/shakacode/react_on_rails/pull/2011) by [justin808](https://github.com/justin808).

lib/generators/react_on_rails/base_generator.rb

@@ -4,10 +4,12 @@
 require "fileutils"
 require_relative "generator_messages"
 require_relative "generator_helper"
+require_relative "js_dependency_manager"
 module ReactOnRails
   module Generators
     class BaseGenerator < Rails::Generators::Base
       include GeneratorHelper
+      include JsDependencyManager
 
       Rails::Generators.hide_namespace(namespace)
       source_root(File.expand_path("templates", __dir__))
@@ -107,7 +109,7 @@ def add_base_gems_to_gemfile
         run "bundle"
       end
 
-      def update_gitignore_for_generated_bundles
+      def update_gitignore_for_auto_registration
         gitignore_path = File.join(destination_root, ".gitignore")
         return unless File.exist?(gitignore_path)
 
@@ -146,123 +148,6 @@ def append_to_spec_rails_helper
 
       private
 
-      def setup_js_dependencies
-        add_js_dependencies
-        install_js_dependencies
-      end
-
-      def add_js_dependencies
-        add_react_on_rails_package
-        add_react_dependencies
-        add_css_dependencies
-        add_dev_dependencies
-      end
-
-      def add_react_on_rails_package
-        major_minor_patch_only = /\A\d+\.\d+\.\d+\z/
-
-        # Try to use package_json gem first, fall back to direct npm commands
-        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..."
-        return if add_npm_dependencies(react_on_rails_pkg)
-
-        puts "Using direct npm commands as fallback"
-        success = system("npm", "install", *react_on_rails_pkg)
-        handle_npm_failure("react-on-rails package", react_on_rails_pkg) unless success
-      end
-
-      def add_react_dependencies
-        puts "Installing React dependencies..."
-        react_deps = %w[
-          react
-          react-dom
-          @babel/preset-react
-          prop-types
-          babel-plugin-transform-react-remove-prop-types
-          babel-plugin-macros
-        ]
-        return if add_npm_dependencies(react_deps)
-
-        success = system("npm", "install", *react_deps)
-        handle_npm_failure("React dependencies", react_deps) unless success
-      end
-
-      def add_css_dependencies
-        puts "Installing CSS handling dependencies..."
-        css_deps = %w[
-          css-loader
-          css-minimizer-webpack-plugin
-          mini-css-extract-plugin
-          style-loader
-        ]
-        return if add_npm_dependencies(css_deps)
-
-        success = system("npm", "install", *css_deps)
-        handle_npm_failure("CSS dependencies", css_deps) unless success
-      end
-
-      def add_dev_dependencies
-        puts "Installing development dependencies..."
-        dev_deps = %w[
-          @pmmmwh/react-refresh-webpack-plugin
-          react-refresh
-        ]
-        return if add_npm_dependencies(dev_deps, dev: true)
-
-        success = system("npm", "install", "--save-dev", *dev_deps)
-        handle_npm_failure("development dependencies", dev_deps, dev: true) unless success
-      end
-
-      def install_js_dependencies
-        # Detect which package manager to use
-        success = if File.exist?(File.join(destination_root, "yarn.lock"))
-                    system("yarn", "install")
-                  elsif File.exist?(File.join(destination_root, "pnpm-lock.yaml"))
-                    system("pnpm", "install")
-                  elsif File.exist?(File.join(destination_root, "package-lock.json")) ||
-                        File.exist?(File.join(destination_root, "package.json"))
-                    # Use npm for package-lock.json or as default fallback
-                    system("npm", "install")
-                  else
-                    true # No package manager detected, skip
-                  end
-
-        unless success
-          GeneratorMessages.add_warning(<<~MSG.strip)
-            ⚠️  JavaScript dependencies installation failed.
-
-            This could be due to network issues or missing package manager.
-            You can install dependencies manually later by running:
-            • npm install (if using npm)
-            • yarn install (if using yarn)
-            • pnpm install (if using pnpm)
-          MSG
-        end
-
-        success
-      end
-
-      def handle_npm_failure(dependency_type, packages, dev: false)
-        install_command = dev ? "npm install --save-dev" : "npm install"
-        GeneratorMessages.add_warning(<<~MSG.strip)
-          ⚠️  Failed to install #{dependency_type}.
-
-          The following packages could not be installed automatically:
-          #{packages.map { |pkg| "  • #{pkg}" }.join("\n")}
-
-          This could be due to network issues or missing package manager.
-          You can install them manually later by running:
-            #{install_command} #{packages.join(' ')}
-        MSG
-      end
-
       def copy_webpack_main_config(base_path, config)
         webpack_config_path = "config/webpack/webpack.config.js"
 

lib/generators/react_on_rails/install_generator.rb

@@ -4,12 +4,14 @@
 require "json"
 require_relative "generator_helper"
 require_relative "generator_messages"
+require_relative "js_dependency_manager"
 
 module ReactOnRails
   module Generators
     # rubocop:disable Metrics/ClassLength
     class InstallGenerator < Rails::Generators::Base
       include GeneratorHelper
+      include JsDependencyManager
 
       # fetch USAGE file for details generator description
       source_root(File.expand_path(__dir__))
@@ -113,10 +115,7 @@ def invoke_generators
       end
 
       def setup_react_dependencies
-        @added_dependencies_to_package_json ||= false
-        @ran_direct_installs ||= false
-        add_js_dependencies
-        install_js_dependencies if @added_dependencies_to_package_json && !@ran_direct_installs
+        setup_js_dependencies
       end
 
       # NOTE: other requirements for existing files such as .gitignore or application.
@@ -366,29 +365,8 @@ def missing_package_manager?
 
       def install_typescript_dependencies
         puts Rainbow("📝 Installing TypeScript dependencies...").yellow
-
-        # Install TypeScript and React type definitions
-        typescript_packages = %w[
-          typescript
-          @types/react
-          @types/react-dom
-          @babel/preset-typescript
-        ]
-
-        # Try using GeneratorHelper first (package manager agnostic)
-        return if add_npm_dependencies(typescript_packages, dev: true)
-
-        # Fallback to npm if GeneratorHelper fails
-        success = system("npm", "install", "--save-dev", *typescript_packages)
-        return if success
-
-        warning = <<~MSG.strip
-          ⚠️  Failed to install TypeScript dependencies automatically.
-
-          Please run manually:
-              npm install --save-dev #{typescript_packages.join(' ')}
-        MSG
-        GeneratorMessages.add_warning(warning)
+        # Delegate to shared module for consistent dependency management
+        add_typescript_dependencies
       end
 
       def create_css_module_types
@@ -450,159 +428,6 @@ def create_typescript_config
         puts Rainbow("✅ Created tsconfig.json").green
       end
 
-      def add_js_dependencies
-        add_react_on_rails_package
-        add_react_dependencies
-        add_css_dependencies
-        add_rspack_dependencies if options.rspack?
-        add_dev_dependencies
-      end
-
-      def add_react_on_rails_package
-        major_minor_patch_only = /\A\d+\.\d+\.\d+\z/
-
-        # Try to use package_json gem first, fall back to direct npm commands
-        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_npm_dependencies(react_on_rails_pkg)
-          @added_dependencies_to_package_json = true
-          return
-        end
-
-        puts "Using direct npm commands as fallback"
-        success = system("npm", "install", *react_on_rails_pkg)
-        @ran_direct_installs = true if success
-        handle_npm_failure("react-on-rails package", react_on_rails_pkg) unless success
-      end
-
-      def add_react_dependencies
-        puts "Installing React dependencies..."
-        react_deps = %w[
-          react
-          react-dom
-          @babel/preset-react
-          prop-types
-          babel-plugin-transform-react-remove-prop-types
-          babel-plugin-macros
-        ]
-        if add_npm_dependencies(react_deps)
-          @added_dependencies_to_package_json = true
-          return
-        end
-
-        success = system("npm", "install", *react_deps)
-        @ran_direct_installs = true if success
-        handle_npm_failure("React dependencies", react_deps) unless success
-      end
-
-      def add_css_dependencies
-        puts "Installing CSS handling dependencies..."
-        css_deps = %w[
-          css-loader
-          css-minimizer-webpack-plugin
-          mini-css-extract-plugin
-          style-loader
-        ]
-        if add_npm_dependencies(css_deps)
-          @added_dependencies_to_package_json = true
-          return
-        end
-
-        success = system("npm", "install", *css_deps)
-        @ran_direct_installs = true if success
-        handle_npm_failure("CSS dependencies", css_deps) unless success
-      end
-
-      def add_rspack_dependencies
-        puts "Installing Rspack core dependencies..."
-        rspack_deps = %w[
-          @rspack/core
-          rspack-manifest-plugin
-        ]
-        if add_npm_dependencies(rspack_deps)
-          @added_dependencies_to_package_json = true
-          return
-        end
-
-        success = system("npm", "install", *rspack_deps)
-        @ran_direct_installs = true if success
-        handle_npm_failure("Rspack dependencies", rspack_deps) unless success
-      end
-
-      def add_dev_dependencies
-        puts "Installing development dependencies..."
-        dev_deps = if options.rspack?
-                     %w[
-                       @rspack/cli
-                       @rspack/plugin-react-refresh
-                       react-refresh
-                     ]
-                   else
-                     %w[
-                       @pmmmwh/react-refresh-webpack-plugin
-                       react-refresh
-                     ]
-                   end
-        if add_npm_dependencies(dev_deps, dev: true)
-          @added_dependencies_to_package_json = true
-          return
-        end
-
-        success = system("npm", "install", "--save-dev", *dev_deps)
-        @ran_direct_installs = true if success
-        handle_npm_failure("development dependencies", dev_deps, dev: true) unless success
-      end
-
-      def install_js_dependencies
-        # Detect which package manager to use
-        success = if File.exist?(File.join(destination_root, "yarn.lock"))
-                    system("yarn", "install")
-                  elsif File.exist?(File.join(destination_root, "pnpm-lock.yaml"))
-                    system("pnpm", "install")
-                  elsif File.exist?(File.join(destination_root, "package-lock.json")) ||
-                        File.exist?(File.join(destination_root, "package.json"))
-                    # Use npm for package-lock.json or as default fallback
-                    system("npm", "install")
-                  else
-                    true # No package manager detected, skip
-                  end
-
-        unless success
-          GeneratorMessages.add_warning(<<~MSG.strip)
-            ⚠️  JavaScript dependencies installation failed.
-
-            This could be due to network issues or missing package manager.
-            You can install dependencies manually later by running:
-            • npm install (if using npm)
-            • yarn install (if using yarn)
-            • pnpm install (if using pnpm)
-          MSG
-        end
-
-        success
-      end
-
-      def handle_npm_failure(dependency_type, packages, dev: false)
-        install_command = dev ? "npm install --save-dev" : "npm install"
-        GeneratorMessages.add_warning(<<~MSG.strip)
-          ⚠️  Failed to install #{dependency_type}.
-
-          The following packages could not be installed automatically:
-          #{packages.map { |pkg| "  • #{pkg}" }.join("\n")}
-
-          This could be due to network issues or missing package manager.
-          You can install them manually later by running:
-            #{install_command} #{packages.join(' ')}
-        MSG
-      end
-
       # Removed: Shakapacker auto-installation logic (now explicit dependency)
 
       # Removed: Shakapacker 8+ is now required as explicit dependency