Integrate missing components from webpack-rails gem

This change incorporates the methods needed to read the webpack
manifest file from the deprecated webpack-rails gem into gitlab
itself. We will now be able to maintain it ourselves and modify
it to do things like listen on unix file sockets for dev-server

config/application.rb

@@ -152,12 +152,18 @@ module Gitlab
     config.active_record.schema_format = :sql
 
     # Configure webpack
+    config.webpack = ActiveSupport::OrderedOptions.new
     config.webpack.config_file = "config/webpack.config.js"
     config.webpack.output_dir  = "public/assets/webpack"
     config.webpack.public_path = "assets/webpack"
+    config.webpack.manifest_filename = "manifest.json"
 
     # Webpack dev server configuration is handled in initializers/static_files.rb
+    config.webpack.dev_server = ActiveSupport::OrderedOptions.new
     config.webpack.dev_server.enabled = false
+    config.webpack.dev_server.host = 'localhost'
+    config.webpack.dev_server.port = 3808
+    config.webpack.dev_server.https = false
 
     config.action_mailer.delivery_job = "ActionMailer::MailDeliveryJob"
 

config/initializers/static_files.rb

@@ -21,9 +21,7 @@ if app.config.public_file_server.enabled
     settings = {
       enabled: true,
       host: dev_server.host,
-      port: dev_server.port,
-      manifest_host: dev_server.host,
-      manifest_port: dev_server.port
+      port: dev_server.port
     }
 
     if Rails.env.development?

lib/gitlab/webpack/manifest.rb

 # frozen_string_literal: true
 
-require 'webpack/rails/manifest'
+require 'net/http'
+require 'uri'
 
 module Gitlab
   module Webpack
-    class Manifest < ::Webpack::Rails::Manifest
-      # Raised if a supplied asset does not exist in the webpack manifest
+    class Manifest
+      # Raised if we can't read our webpack manifest for whatever reason
+      class ManifestLoadError < StandardError
+        def initialize(message, orig)
+          super "#{message} (original error #{orig})"
+        end
+      end
+
+      # Raised if webpack couldn't build one of your entry points
+      class WebpackError < StandardError
+        def initialize(errors)
+          super "Error in webpack compile, details follow below:\n#{errors.join("\n\n")}"
+        end
+      end
+
+      # Raised if a supplied entry point does not exist in the webpack manifest
       AssetMissingError = Class.new(StandardError)
 
       class << self
         def entrypoint_paths(source)
-          raise ::Webpack::Rails::Manifest::WebpackError, manifest["errors"] unless manifest_bundled?
+          raise WebpackError, manifest["errors"] unless manifest_bundled?
 
           dll_assets = manifest.fetch("dllAssets", [])
           entrypoint = manifest["entrypoints"][source]
@@ -20,10 +35,79 @@ module Gitlab
             [dll_assets, entrypoint["assets"]].flatten.reject { |p| p =~ /.*\.map$/ }.map do |p|
               "/#{::Rails.configuration.webpack.public_path}/#{p}"
             end
+          else
+            raise AssetMissingError, "Can't find asset '#{source}' in webpack manifest"
+          end
+        end
+
+        def asset_paths(source)
+          raise WebpackError, manifest["errors"] unless manifest_bundled?
+
+          paths = manifest["assetsByChunkName"][source]
+          if paths
+            # Can be either a string or an array of strings.
+            # Do not include source maps as they are not javascript
+            [paths].flatten.reject { |p| p =~ /.*\.map$/ }.map do |p|
+              "/#{::Rails.configuration.webpack.public_path}/#{p}"
+            end
           else
             raise AssetMissingError, "Can't find entry point '#{source}' in webpack manifest"
           end
         end
+
+        private
+
+        def manifest_bundled?
+          !manifest["errors"].any? { |error| error.include? "Module build failed" }
+        end
+
+        def manifest
+          if ::Rails.configuration.webpack.dev_server.enabled
+            # Don't cache if we're in dev server mode, manifest may change ...
+            load_manifest
+          else
+            # ... otherwise cache at class level, as JSON loading/parsing can be expensive
+            @manifest ||= load_manifest
+          end
+        end
+
+        def load_manifest
+          data = if ::Rails.configuration.webpack.dev_server.enabled
+                   load_dev_server_manifest
+                 else
+                   load_static_manifest
+                 end
+
+          Gitlab::Json.parse(data)
+        end
+
+        def load_dev_server_manifest
+          host = ::Rails.configuration.webpack.dev_server.host
+          port = ::Rails.configuration.webpack.dev_server.port
+          http = Net::HTTP.new(host, port)
+          http.use_ssl = ::Rails.configuration.webpack.dev_server.https
+          http.verify_mode = OpenSSL::SSL::VERIFY_NONE
+          http.get(dev_server_path).body
+        rescue => e
+          raise ManifestLoadError.new("Could not load manifest from webpack-dev-server at http://#{host}:#{port}#{dev_server_path} - is it running, and is stats-webpack-plugin loaded?", e)
+        end
+
+        def load_static_manifest
+          File.read(static_manifest_path)
+        rescue => e
+          raise ManifestLoadError.new("Could not load compiled manifest from #{static_manifest_path} - have you run `rake webpack:compile`?", e)
+        end
+
+        def static_manifest_path
+          ::Rails.root.join(
+            ::Rails.configuration.webpack.output_dir,
+            ::Rails.configuration.webpack.manifest_filename
+          )
+        end
+
+        def dev_server_path
+          "/#{::Rails.configuration.webpack.public_path}/#{::Rails.configuration.webpack.manifest_filename}"
+        end
       end
     end
   end

lib/tasks/gitlab/assets.rake

@@ -81,7 +81,7 @@ namespace :gitlab do
 
       if head_assets_md5 != master_assets_md5 || !public_assets_webpack_dir_exists
         FileUtils.rm_r(Tasks::Gitlab::Assets::PUBLIC_ASSETS_WEBPACK_DIR) if public_assets_webpack_dir_exists
-        Rake::Task['webpack:compile'].invoke
+        system('yarn webpack')
       end
     end