feat(WebpackerManifestContainer) use webpack-dev-server if detected

Author: rmosolgo

lib/react/server_rendering/sprockets_renderer.rb

@@ -94,10 +94,10 @@ def assets_precompiled?
       def asset_container_class
         if self.class.asset_container_class.present?
           self.class.asset_container_class
+        elsif WebpackerManifestContainer.compatible?
+          WebpackerManifestContainer
         elsif assets_precompiled?
-          if WebpackerManifestContainer.compatible?
-            WebpackerManifestContainer
-          elsif ManifestContainer.compatible?
+          if ManifestContainer.compatible?
             ManifestContainer
           elsif YamlManifestContainer.compatible?
             YamlManifestContainer

lib/react/server_rendering/webpacker_manifest_container.rb

@@ -1,20 +1,26 @@
+require "open-uri"
+
 module React
   module ServerRendering
     # Get a compiled file from Webpacker
     class WebpackerManifestContainer
       def find_asset(logical_path)
         asset_path = Webpacker::Manifest.lookup(logical_path) # raises if not found
-        full_path = File.join(
-          # TODO: using `.parent` here won't work for nonstandard configurations
-          Webpacker::Configuration.output_path.parent,
-          asset_path
-        )
-        # TODO: webpacker-dev-server points these at localhost:8080
-        File.read(full_path)
+        if asset_path.start_with?("http")
+          # TODO: this includes webpack-dev-server code which causes ExecJS to 💥
+          dev_server_asset = open(asset_path).read
+        else
+          full_path = File.join(
+            # TODO: using `.parent` here won't work for nonstandard configurations
+            Webpacker::Configuration.output_path.parent,
+            asset_path
+          )
+          File.read(full_path)
+        end
       end
 
       def self.compatible?
-        defined?(Webpacker)
+        !!defined?(Webpacker)
       end
     end
   end

test/react/rails/webpacker_test.rb

@@ -6,6 +6,7 @@ class ReactRailsWebpackerTest < ActionDispatch::IntegrationTest
 
     setup do
       Capybara.current_driver = Capybara.javascript_driver
+      WebpackerHelpers.compile
     end
 
     teardown do

test/react/server_rendering/webpacker_manifest_container_test.rb

@@ -1,14 +1,59 @@
 require "test_helper"
+require "open-uri"
 
 WebpackerHelpers.when_webpacker_available do
   class WebpackerManifestContainerTest < ActiveSupport::TestCase
+    setup do
+      WebpackerHelpers.clear_webpacker_packs
+    end
+
     test "it loads JS from the webpacker container" do
+      WebpackerHelpers.compile
+      container = React::ServerRendering::WebpackerManifestContainer.new
+      js_file = container.find_asset("application.js")
+      # Main file:
+      assert_includes js_file, "ReactRailsUJS.loadContext(ctx)"
+      # Bundled dependencies:
+      assert_includes js_file, "ExportDefaultComponent"
+    end
+
+    def test_it_loads_from_webpack_dev_server
+      webpack_dev_server = fork do
+        Dir.chdir("test/dummy") do
+          exec "./bin/webpack-dev-server RAILS_ENV=development"
+        end
+      end
+
+      detected_dev_server = false
+      20.times do |i|
+        begin
+          # Make sure that the manifest has been updated:
+          Webpacker::Manifest.load("./test/dummy/public/packs/manifest.json")
+          webpack_manifest = Webpacker::Manifest.instance.data
+          example_asset_path = webpack_manifest.values.first
+          assert_includes example_asset_path, "http://localhost:8080"
+          # Make sure the dev server is up:
+          open("http://localhost:8080/application.js")
+          detected_dev_server = true
+          break
+        rescue StandardError => err
+          sleep 0.5
+        end
+      end
+
+      # If we didn't hook up with a dev server after 10s,
+      # fail loudly.
+      assert detected_dev_server
+
       container = React::ServerRendering::WebpackerManifestContainer.new
       js_file = container.find_asset("application.js")
       # Main file:
       assert_includes js_file, "ReactRailsUJS.loadContext(ctx)"
       # Bundled dependencies:
       assert_includes js_file, "ExportDefaultComponent"
+    ensure
+      Process.kill(9, webpack_dev_server)
+      Process.wait
     end
   end
 end

test/support/webpacker_helpers.rb

@@ -3,16 +3,19 @@ module WebpackerHelpers
 
   def when_webpacker_available
     if defined?(Webpacker)
-      clear_webpacker_packs
-      Dir.chdir("./test/dummy") do
-        Rake::Task['webpacker:compile'].invoke
-      end
-      # Reload cached JSON manifest:
-      Webpacker::Manifest.load
       yield
     end
   end
 
+  def compile
+    clear_webpacker_packs
+    Dir.chdir("./test/dummy") do
+      Rake::Task['webpacker:compile'].invoke
+    end
+    # Reload cached JSON manifest:
+    Webpacker::Manifest.load
+  end
+
   def clear_webpacker_packs
     packs_directory = File.expand_path("../dummy/public/packs", __FILE__)
     FileUtils.rm_rf(packs_directory)