feat: support Shakapacker v9 (#627)

Shakapacker v9 brings support for Rspack as an alternative to webpack,
and changes the default transpiler from Babel to SWC.

While it would be interesting to explore these new options, for now I've
had us stick with webpack and babel.

See [here for the upgrade
notes](https://github.com/shakacode/shakapacker/blob/main/docs/v9_upgrade.md)

Author: G-Rath

variants/frontend-base-typescript/types.d.ts

@@ -12,3 +12,14 @@ declare module '*.jpg' {
   const content: string;
   export default content;
 }
+
+// todo: even though shakapacker ships with its own types, it currently types
+//  itself as "any" which will hopefully change in a future version
+declare module 'shakapacker' {
+  import { Configuration } from 'webpack';
+
+  export function generateWebpackConfig(
+    extraConfig?: Configuration
+  ): Configuration;
+  export * from 'webpack-merge';
+}

variants/frontend-base/template.rb

@@ -18,17 +18,24 @@
 
 run "rails shakapacker:install"
 
-# ensure the latest major versions of Shakapacker's peer dependencies are installed
-#
-# TODO: remove this once https://github.com/shakacode/shakapacker/pull/576 is landed
+# install dependencies for babel and webpack
 add_js_dependencies [
-  "babel-loader@10",
-  "compression-webpack-plugin@11",
-  "webpack-assets-manifest@6",
-  "webpack-cli@6",
-  "webpack-merge@6"
+  "@babel/core",
+  "@babel/plugin-transform-runtime",
+  "@babel/preset-env",
+  "@babel/runtime",
+  "babel-loader",
+  "compression-webpack-plugin",
+  "css-loader",
+  "mini-css-extract-plugin",
+  "sass-loader",
+  "style-loader",
+  "terser-webpack-plugin",
+  "webpack-assets-manifest",
+  "webpack-cli",
+  "webpack-merge"
 ]
-add_js_dependencies ["webpack-dev-server@5"], type: :dev
+add_js_dependencies ["webpack-dev-server"], type: :dev
 
 # this is added by shakapacker:install, but we've already got one (with some extra tags)
 # in our template, so remove theirs otherwise the app will error when rendering this
@@ -48,6 +55,7 @@
 copy_file "config/webpack/webpack.config.js", force: true
 
 gsub_file! "config/shakapacker.yml", "cache_path: tmp/shakapacker", "cache_path: tmp/cache/shakapacker"
+gsub_file! "config/shakapacker.yml", "javascript_transpiler: 'swc'", "javascript_transpiler: 'babel'"
 gsub_file! "config/shakapacker.yml", "source_path: app/javascript", "source_path: app/frontend"
 
 old_shakapacker_test_compile_snippet = <<~EO_OLD