Add Shakapacker precompile hook template for generator

.github/workflows/examples.yml

@@ -66,8 +66,10 @@ jobs:
         uses: actions/setup-node@v4
         with:
           node-version: 20
-          cache: yarn
-          cache-dependency-path: '**/yarn.lock'
+          # TODO: Re-enable yarn caching once Node.js V8 cache crash is fixed
+          # Tracking: https://github.com/actions/setup-node/issues/1028
+          # cache: yarn
+          # cache-dependency-path: '**/yarn.lock'
       - name: Print system information
         run: |
           echo "Linux release: "; cat /etc/issue

lib/generators/react_on_rails/base_generator.rb

@@ -37,12 +37,16 @@ def copy_base_files
                         app/views/layouts/hello_world.html.erb
                         Procfile.dev
                         Procfile.dev-static-assets
-                        Procfile.dev-prod-assets]
+                        Procfile.dev-prod-assets
+                        bin/shakapacker-precompile-hook]
         base_templates = %w[config/initializers/react_on_rails.rb]
         base_files.each { |file| copy_file("#{base_path}#{file}", file) }
         base_templates.each do |file|
           template("#{base_path}/#{file}.tt", file)
         end
+
+        # Make the hook script executable (copy_file guarantees it exists)
+        File.chmod(0o755, File.join(destination_root, "bin/shakapacker-precompile-hook"))
       end
 
       def copy_js_bundle_files

lib/generators/react_on_rails/templates/base/base/bin/shakapacker-precompile-hook

@@ -0,0 +1,30 @@
+#!/usr/bin/env ruby
+# frozen_string_literal: true
+
+# Shakapacker precompile hook for React on Rails
+#
+# This script runs before webpack compilation to generate pack files
+# for auto-bundled components. It's called automatically by Shakapacker
+# when configured in config/shakapacker.yml:
+#   precompile_hook: 'bin/shakapacker-precompile-hook'
+#
+# Emoji Scheme:
+#   🔄 = Running/in-progress
+#   ✅ = Success
+#   ❌ = Error
+
+# Skip validation during precompile hook execution
+# The hook runs early in the build process, potentially before full Rails initialization,
+# and doesn't need package version validation since it's part of the build itself
+ENV["REACT_ON_RAILS_SKIP_VALIDATION"] = "true"
+
+require_relative "../config/environment"
+
+begin
+  puts Rainbow("🔄 Running React on Rails precompile hook...").cyan
+  ReactOnRails::PacksGenerator.instance.generate_packs_if_stale
+rescue StandardError => e
+  warn Rainbow("❌ Error in precompile hook: #{e.message}").red
+  warn e.backtrace.first(5).join("\n")
+  exit 1
+end

lib/generators/react_on_rails/templates/base/base/config/shakapacker.yml

@@ -42,6 +42,11 @@ default: &default
   # Raises an error if there is a mismatch in the shakapacker gem and npm package being used
   ensure_consistent_versioning: true
 
+  # Hook to run before webpack compilation (e.g., for generating dynamic entry points)
+  # SECURITY: Only reference trusted scripts within your project. Ensure the hook path
+  # points to a file within the project root that you control.
+  precompile_hook: 'bin/shakapacker-precompile-hook'
+
   # Select whether the compiler will use SHA digest ('digest' option) or most recent modified timestamp ('mtime') to determine freshness
   compiler_strategy: digest
 

lib/react_on_rails/dev/server_manager.rb

@@ -248,7 +248,7 @@ def help_mode_details
           <<~MODES
             #{Rainbow('🔥 HMR Development mode (default)').cyan.bold} - #{Rainbow('Procfile.dev').green}:
             #{Rainbow('•').yellow} #{Rainbow('Hot Module Replacement (HMR) enabled').white}
-            #{Rainbow('•').yellow} #{Rainbow('React on Rails pack generation before Procfile start').white}
+            #{Rainbow('•').yellow} #{Rainbow('React on Rails pack generation (via precompile hook or bin/dev)').white}
             #{Rainbow('•').yellow} #{Rainbow('Webpack dev server for fast recompilation').white}
             #{Rainbow('•').yellow} #{Rainbow('Source maps for debugging').white}
             #{Rainbow('•').yellow} #{Rainbow('May have Flash of Unstyled Content (FOUC)').white}
@@ -257,15 +257,15 @@ def help_mode_details
 
             #{Rainbow('📦 Static development mode').cyan.bold} - #{Rainbow('Procfile.dev-static-assets').green}:
             #{Rainbow('•').yellow} #{Rainbow('No HMR (static assets with auto-recompilation)').white}
-            #{Rainbow('•').yellow} #{Rainbow('React on Rails pack generation before Procfile start').white}
+            #{Rainbow('•').yellow} #{Rainbow('React on Rails pack generation (via precompile hook or bin/dev)').white}
             #{Rainbow('•').yellow} #{Rainbow('Webpack watch mode for auto-recompilation').white}
             #{Rainbow('•').yellow} #{Rainbow('CSS extracted to separate files (no FOUC)').white}
             #{Rainbow('•').yellow} #{Rainbow('Development environment (faster builds than production)').white}
             #{Rainbow('•').yellow} #{Rainbow('Source maps for debugging').white}
             #{Rainbow('•').yellow} #{Rainbow('Access at:').white} #{Rainbow('http://localhost:3000/<route>').cyan.underline}
 
             #{Rainbow('🏭 Production-assets mode').cyan.bold} - #{Rainbow('Procfile.dev-prod-assets').green}:
-            #{Rainbow('•').yellow} #{Rainbow('React on Rails pack generation before Procfile start').white}
+            #{Rainbow('•').yellow} #{Rainbow('React on Rails pack generation (via precompile hook or assets:precompile)').white}
             #{Rainbow('•').yellow} #{Rainbow('Asset precompilation with NODE_ENV=production (webpack optimizations)').white}
             #{Rainbow('•').yellow} #{Rainbow('RAILS_ENV=development by default for assets:precompile (avoids credentials)').white}
             #{Rainbow('•').yellow} #{Rainbow('Use --rails-env=production for assets:precompile only (not server processes)').white}
@@ -281,16 +281,20 @@ def help_mode_details
         def run_production_like(_verbose: false, route: nil, rails_env: nil)
           procfile = "Procfile.dev-prod-assets"
 
+          features = [
+            "Precompiling assets with production optimizations",
+            "Running Rails server on port 3001",
+            "No HMR (Hot Module Replacement)",
+            "CSS extracted to separate files (no FOUC)"
+          ]
+
+          # NOTE: Pack generation happens automatically during assets:precompile
+          # either via precompile hook or via the configuration.rb adjust_precompile_task
+
           print_procfile_info(procfile, route: route)
           print_server_info(
             "🏭 Starting production-like development server...",
-            [
-              "Generating React on Rails packs",
-              "Precompiling assets with production optimizations",
-              "Running Rails server on port 3001",
-              "No HMR (Hot Module Replacement)",
-              "CSS extracted to separate files (no FOUC)"
-            ],
+            features,
             3001,
             route: route
           )
@@ -409,15 +413,22 @@ def run_production_like(_verbose: false, route: nil, rails_env: nil)
 
         def run_static_development(procfile, verbose: false, route: nil)
           print_procfile_info(procfile, route: route)
+
+          features = [
+            "Using shakapacker --watch (no HMR)",
+            "CSS extracted to separate files (no FOUC)",
+            "Development environment (source maps, faster builds)",
+            "Auto-recompiles on file changes"
+          ]
+
+          # Add pack generation info if not using precompile hook
+          unless ReactOnRails::PackerUtils.shakapacker_precompile_hook_configured?
+            features.unshift("Generating React on Rails packs")
+          end
+
           print_server_info(
             "⚡ Starting development server with static assets...",
-            [
-              "Generating React on Rails packs",
-              "Using shakapacker --watch (no HMR)",
-              "CSS extracted to separate files (no FOUC)",
-              "Development environment (source maps, faster builds)",
-              "Auto-recompiles on file changes"
-            ],
+            features,
             route: route
           )
 

lib/react_on_rails/packer_utils.rb

@@ -197,8 +197,8 @@ def self.extract_precompile_hook
       config_data = ::Shakapacker.config.send(:data)
 
       # Try symbol keys first (Shakapacker's internal format), then fall back to string keys
-      # Note: Currently only one hook value is supported, but this will change to support lists
-      config_data&.dig(:hooks, :precompile) || config_data&.dig("hooks", "precompile")
+      # The key is 'precompile_hook' at the top level of the config
+      config_data&.[](:precompile_hook) || config_data&.[]("precompile_hook")
     end
 
     def self.hook_contains_generate_packs?(hook_value)

spec/dummy/config/shakapacker.yml

@@ -9,10 +9,6 @@ default: &default
   # SWC has issues with PropTypes handling
   javascript_transpiler: babel
 
-  # Hook to run before compilation (e.g., for ReScript builds, pack generation)
-  # See: https://github.com/shakacode/shakapacker/blob/main/docs/precompile_hook.md
-  precompile_hook: bin/shakapacker-precompile-hook
-
   cache_path: tmp/cache/shakapacker
   webpack_compile_output: false
   ensure_consistent_versioning: true
@@ -25,6 +21,11 @@ default: &default
   cache_manifest: false
   nested_entries: true
 
+  # Hook to run before webpack compilation (e.g., for generating dynamic entry points)
+  # SECURITY: Only reference trusted scripts within your project. Ensure the hook path
+  # points to a file within the project root that you control.
+  precompile_hook: 'bin/shakapacker-precompile-hook'
+
 development:
   <<: *default
   # Turn this to true if you want to use the rails/shakapacker check that the test