fix: Add Rspack and TypeScript support to shared JS dependency manager

This commit addresses critical issues identified in code review:

### 1. Added Missing Rspack Support
- **Problem**: Rspack dependencies were lost during the refactor to shared module
- **Solution**: Added RSPACK_DEPENDENCIES and RSPACK_DEV_DEPENDENCIES constants
- **Implementation**:
  - Created `add_rspack_dependencies` method in shared module
  - Modified `add_dev_dependencies` to use Rspack-specific dev deps when `options.rspack?` is true
  - Conditional installation in `add_js_dependencies` checks for `options.rspack?`
- **Impact**: Users with --rspack flag now get proper Rspack packages installed

### 2. Fixed TypeScript Dependency Consistency
- **Problem**: TypeScript dependency handling was inconsistent with shared module pattern
- **Solution**: Extracted TypeScript dependencies into shared module
- **Implementation**:
  - Added TYPESCRIPT_DEPENDENCIES constant
  - Created `add_typescript_dependencies` method following same pattern as other deps
  - Updated `install_generator.rb` to delegate to shared method
  - Removed manual instance variable setting
- **Impact**: Consistent error handling and pattern across all dependency types

### 3. Documented Unconditional Install Behavior
- **Problem**: Unclear why `install_js_dependencies` is called unconditionally
- **Solution**: Added comprehensive documentation explaining the design decision
- **Rationale**:
  - package_json gem's install is idempotent - only installs what's needed
  - Prevents edge cases where package.json modified but dependencies not installed
  - Safer and simpler than conditional logic that could miss cases
- **Impact**: Future maintainers understand why the unconditional call is correct

### 4. Enhanced Module Documentation
- **Updated Instance Variables section**: Clarified module initializes variables
- **Added Optional Methods section**: Documents options.rspack? and options.typescript?
- **Added Installation Behavior section**: Explains idempotent install behavior
- **Impact**: Clear contract for classes including the module

### 5. Constants Usage Verification
- Verified all constants (REACT_DEPENDENCIES, CSS_DEPENDENCIES, DEV_DEPENDENCIES) are properly used
- All dependency methods use their corresponding constants correctly

### Testing
- ✅ All tests pass (6 examples, 0 failures)
- ✅ bundle exec rubocop passes with zero offenses
- ✅ Git hooks (pre-commit, pre-push) verified clean

### Files Changed
- `lib/generators/react_on_rails/js_dependency_manager.rb`: Added Rspack, TypeScript support, enhanced docs
- `lib/generators/react_on_rails/install_generator.rb`: Simplified TypeScript method to delegate to shared module

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

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

Author: justin808

lib/generators/react_on_rails/install_generator.rb

@@ -365,23 +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
-        ]
-
-        # Use the shared dependency management approach via GeneratorHelper
-        unless add_npm_dependencies(typescript_packages, dev: true)
-          # This should not happen since package_json is always available via shakapacker
-          raise "Failed to add TypeScript dependencies (#{typescript_packages.join(', ')}) via package_json gem. " \
-                "This indicates shakapacker dependency may not be properly installed."
-        end
-
-        @added_dependencies_to_package_json = true
+        # Delegate to shared module for consistent dependency management
+        add_typescript_dependencies
       end
 
       def create_css_module_types

lib/generators/react_on_rails/js_dependency_manager.rb

@@ -11,16 +11,28 @@ module Generators
     # Since react_on_rails requires shakapacker, and shakapacker includes
     # package_json as a dependency, the package_json gem is always available.
     #
-    # == Required Instance Variables
-    # Including classes must support these instance variables:
+    # == Instance Variables
+    # The module initializes and manages these instance variables:
     # - @added_dependencies_to_package_json: Boolean tracking if package_json gem was used
+    #   (initialized by setup_js_dependencies using `unless defined?` pattern)
     #
     # == Required Methods
     # Including classes must include GeneratorHelper module which provides:
     # - add_npm_dependencies(packages, dev: false): Add packages via package_json gem
     # - package_json: Access to PackageJson instance (always available via shakapacker)
     # - destination_root: Generator destination directory
     #
+    # == Optional Methods
+    # Including classes may define:
+    # - options.rspack?: Returns true if --rspack flag is set (for Rspack support)
+    # - options.typescript?: Returns true if --typescript flag is set (for TypeScript support)
+    #
+    # == Installation Behavior
+    # The module ALWAYS runs package manager install after adding dependencies.
+    # This is safe because package_json gem's install is idempotent - it only
+    # installs what's actually needed from package.json. This prevents edge cases
+    # where package.json was modified but dependencies weren't installed.
+    #
     # == Usage
     # Include this module in generator classes and call setup_js_dependencies
     # to handle all JS dependency installation via package_json gem.
@@ -43,26 +55,56 @@ module JsDependencyManager
         style-loader
       ].freeze
 
-      # Development-only dependencies for hot reloading
+      # Development-only dependencies for hot reloading (Webpack)
       DEV_DEPENDENCIES = %w[
         @pmmmwh/react-refresh-webpack-plugin
         react-refresh
       ].freeze
 
+      # Rspack core dependencies (only installed when --rspack flag is used)
+      RSPACK_DEPENDENCIES = %w[
+        @rspack/core
+        rspack-manifest-plugin
+      ].freeze
+
+      # Rspack development dependencies for hot reloading
+      RSPACK_DEV_DEPENDENCIES = %w[
+        @rspack/cli
+        @rspack/plugin-react-refresh
+        react-refresh
+      ].freeze
+
+      # TypeScript dependencies (only installed when --typescript flag is used)
+      TYPESCRIPT_DEPENDENCIES = %w[
+        typescript
+        @types/react
+        @types/react-dom
+        @babel/preset-typescript
+      ].freeze
+
       private
 
       def setup_js_dependencies
         # Initialize instance variable if not already defined by including class
         # This ensures safe operation when the module is first included
         @added_dependencies_to_package_json = false unless defined?(@added_dependencies_to_package_json)
         add_js_dependencies
+
+        # Always run install to ensure all dependencies are properly installed.
+        # The package_json gem's install method is idempotent and safe to call
+        # even if packages were already added - it will only install what's needed.
+        # This ensures edge cases where package.json was modified but install wasn't
+        # run are handled correctly.
         install_js_dependencies
       end
 
       def add_js_dependencies
         add_react_on_rails_package
         add_react_dependencies
         add_css_dependencies
+        # Rspack dependencies are only added when --rspack flag is used
+        add_rspack_dependencies if respond_to?(:options) && options.rspack?
+        # Dev dependencies vary based on bundler choice
         add_dev_dependencies
       end
 
@@ -104,14 +146,45 @@ def add_css_dependencies
         end
       end
 
+      def add_rspack_dependencies
+        puts "Installing Rspack core dependencies..."
+
+        if add_js_dependencies_batch(RSPACK_DEPENDENCIES)
+          @added_dependencies_to_package_json = true
+        else
+          # This should not happen since package_json is always available via shakapacker
+          raise "Failed to add Rspack dependencies (#{RSPACK_DEPENDENCIES.join(', ')}) via package_json gem. " \
+                "This indicates shakapacker dependency may not be properly installed."
+        end
+      end
+
+      def add_typescript_dependencies
+        puts "Installing TypeScript dependencies..."
+
+        if add_js_dependencies_batch(TYPESCRIPT_DEPENDENCIES, dev: true)
+          @added_dependencies_to_package_json = true
+        else
+          # This should not happen since package_json is always available via shakapacker
+          raise "Failed to add TypeScript dependencies (#{TYPESCRIPT_DEPENDENCIES.join(', ')}) via package_json gem. " \
+                "This indicates shakapacker dependency may not be properly installed."
+        end
+      end
+
       def add_dev_dependencies
         puts "Installing development dependencies..."
 
-        if add_js_dependencies_batch(DEV_DEPENDENCIES, dev: true)
+        # Use Rspack-specific dev dependencies if --rspack flag is set
+        dev_deps = if respond_to?(:options) && options.rspack?
+                     RSPACK_DEV_DEPENDENCIES
+                   else
+                     DEV_DEPENDENCIES
+                   end
+
+        if add_js_dependencies_batch(dev_deps, dev: true)
           @added_dependencies_to_package_json = true
         else
           # This should not happen since package_json is always available via shakapacker
-          raise "Failed to add development dependencies (#{DEV_DEPENDENCIES.join(', ')}) via package_json gem. " \
+          raise "Failed to add development dependencies (#{dev_deps.join(', ')}) via package_json gem. " \
                 "This indicates shakapacker dependency may not be properly installed."
         end
       end