Workarounds for Yarn not playing nicely on Windows

CHANGELOG.md

@@ -11,6 +11,8 @@
     host: localhost
 ```
 
+- On Windows, `ruby bin/webpacker` and `ruby bin/webpacker-dev-server` will now bypass yarn, and execute via `node_modules/.bin` directly - [#584](https://github.com/rails/webpacker/pull/584)
+
 ### Breaking changes
 
 - Add `compile` option to `config/webpacker.yml` for configuring lazy compilation of packs when a file under tracked paths is changed [#503](https://github.com/rails/webpacker/pull/503). To enable expected behavior, update `config/webpacker.yml`:

README.md

@@ -72,6 +72,7 @@ in which case you may not even need the asset pipeline. This is mostly relevant
     - [Error: listen EADDRINUSE 0.0.0.0:8080](#error-listen-eaddrinuse-00008080)
     - [throw er; // Unhandled 'error' event](#throw-er--unhandled-error-event)
     - [webpack or webpack-dev-server not found](#webpack-or-webpack-dev-server-not-found)
+    - [Running Webpack on Windows](#running-webpack-on-windows)
 - [Wishlist](#wishlist)
 - [License](#license)
 
@@ -1185,6 +1186,17 @@ bundle config --delete bin
 ./bin/rails app:update:bin # or rails app:update:bin
 ```
 
+##### Running Webpack on Windows
+
+If you are running Webpack on Windows, your command shell may not be able to interpret the preferred interpreter
+for the scripts generated in `bin/webpack` and `bin/webpack-dev-server`. Instead you'll want to run the scripts
+manually with Ruby:
+
+```
+C:\path>ruby bin\webpack
+C:\path>ruby bin\webpack-dev-server
+```
+
 ## Wishlist
 
 - HMR - [#188](https://github.com/rails/webpacker/issues/188)

lib/install/bin/webpack-dev-server.tt

@@ -57,8 +57,14 @@ newenv = {
   "ASSET_HOST" => DEV_SERVER_ADDR.shellescape
 }.freeze
 
-cmdline = ["yarn", "run", "webpack-dev-server", "--", "--progress", "--color", "--config",
+if Gem.win_platform?
+  # Workaround for yarn not playing nicely with path separators
+  cmdline = ["#{NODE_MODULES_PATH}/.bin/webpack-dev-server", "--progress", "--color", "--config",
 WEBPACK_CONFIG, "--host", LISTEN_IP_ADDR, "--port", PORT.to_s] + ARGV
+else
+  cmdline = ["yarn", "run", "webpack-dev-server", "--", "--progress", "--color", "--config",
+WEBPACK_CONFIG, "--host", LISTEN_IP_ADDR, "--port", PORT.to_s] + ARGV
+end
 
 Dir.chdir(APP_PATH) do
   exec newenv, *cmdline

lib/install/bin/webpack.tt

@@ -20,7 +20,12 @@ unless File.exist?(WEBPACK_CONFIG)
 end
 
 newenv  = { "NODE_PATH" => NODE_MODULES_PATH.shellescape }
-cmdline = ["yarn", "run", "webpack", "--", "--config", WEBPACK_CONFIG] + ARGV
+if Gem.win_platform?
+  # Workaround for yarn not playing nicely with path separators
+  cmdline = ["#{NODE_MODULES_PATH}/.bin/webpack", "--config", WEBPACK_CONFIG] + ARGV
+else
+  cmdline = ["yarn", "run", "webpack", "--", "--config", WEBPACK_CONFIG] + ARGV
+end
 
 Dir.chdir(APP_PATH) do
   exec newenv, *cmdline