Add Bun support (#167)

* Add Bun support

* Tweak README

* Tweak README for clarity

Author: terracatta

README.md

@@ -1,36 +1,41 @@
 # JavaScript Bundling for Rails
 
-Use [esbuild](https://esbuild.github.io), [rollup.js](https://rollupjs.org), or [Webpack](https://webpack.js.org) to bundle your JavaScript, then deliver it via the asset pipeline in Rails. This gem provides installers to get you going with the bundler of your choice in a new Rails application, and a convention to use `app/assets/builds` to hold your bundled output as artifacts that are not checked into source control (the installer adds this directory to `.gitignore` by default).
+Use [Bun](https://bun.sh), [esbuild](https://esbuild.github.io), [rollup.js](https://rollupjs.org), or [Webpack](https://webpack.js.org) to bundle your JavaScript, then deliver it via the asset pipeline in Rails. This gem provides installers to get you going with the bundler of your choice in a new Rails application, and a convention to use `app/assets/builds` to hold your bundled output as artifacts that are not checked into source control (the installer adds this directory to `.gitignore` by default).
 
 You develop using this approach by running the bundler in watch mode in a terminal with `yarn build --watch` (and your Rails server in another, if you're not using something like [puma-dev](https://github.com/puma/puma-dev)). You can also use `./bin/dev`, which will start both the Rails server and the JS build watcher (along with a CSS build watcher, if you're also using `cssbundling-rails`).
 
 Whenever the bundler detects changes to any of the JavaScript files in your project, it'll bundle `app/javascript/application.js` into `app/assets/builds/application.js` (and all other entry points configured). You can refer to the build output in your layout using the standard asset pipeline approach with `<%= javascript_include_tag "application", defer: true %>`.
 
-When you deploy your application to production, the `javascript:build` task attaches to the `assets:precompile` task to ensure that all your package dependencies from `package.json` have been installed via yarn, and then runs `yarn build` to process all the entry points, as it would in development. The latter files are then picked up by the asset pipeline, digested, and copied into public/assets, as any other asset pipeline file.
+When you deploy your application to production, the `javascript:build` task attaches to the `assets:precompile` task to ensure that all your package dependencies from `package.json` have been installed via your javascript package manager (bun or yarn), and then runs the build script defined in `package.json` to process all the entry points, as it would in development. The latter files are then picked up by the asset pipeline, digested, and copied into public/assets, as any other asset pipeline file.
 
 This also happens in testing where the bundler attaches to the `test:prepare` task to ensure the JavaScript has been bundled before testing commences. If your testing library of choice does not call the `test:prepare` Rake task, ensure that your test suite runs `javascript:build` to bundle JavaScript before testing commences.
 
 That's it!
 
-You can configure your bundler options in the `build` script in `package.json` or via the installer-generated `rollup.config.js` for rollup.js or `webpack.config.json` for Webpack (esbuild does not have a default configuration format, and we don't intend to use esbuild as an API in order to hack around it).
+You can configure your bundler options in the `build` script in `package.json` or via the installer-generated `bun.config.js` for Bun, `rollup.config.js` for rollup.js or `webpack.config.json` for Webpack (esbuild does not have a default configuration format, and we don't intend to use esbuild as an API in order to hack around it).
 
 If you're already using [`webpacker`](https://github.com/rails/webpacker) and you're wondering if you should migrate to `jsbundling-rails`, have a look at [the high-level comparison](./docs/comparison_with_webpacker.md). If you're looking to migrate from webpacker, see the [migration guide](https://github.com/rails/jsbundling-rails/blob/main/docs/switch_from_webpacker.md).
 
 If you want to use webpack features like [code splitting](https://webpack.js.org/guides/code-splitting/) and [hot module reloading](https://webpack.js.org/concepts/hot-module-replacement/), consider using the official fork of `webpacker`, [`shakapacker`](https://github.com/shakacode/shakapacker).
 
 ## Installation
+If you are installing esbuild, rollup, or webpack, you must already have node
+and yarn installed on your system. You will also need npx version 7.1.0 or later.
 
-You must already have node and yarn installed on your system. You will also need npx version 7.1.0 or later. Then run:
+If you are using Bun, then you must have the Bun runtime already installed on
+your system.
+
+To get started run:
 
 ```
 ./bin/bundle add jsbundling-rails
 ```
 
 ```
-./bin/rails javascript:install:[esbuild|rollup|webpack]
+./bin/rails javascript:install:[bun|esbuild|rollup|webpack]
 ```
 
-Or, in Rails 7+, you can preconfigure your new application to use a specific bundler with `rails new myapp -j [esbuild|rollup|webpack]`.
+Or, in Rails 7+, you can preconfigure your new application to use a specific bundler with `rails new myapp -j [bun|esbuild|rollup|webpack]`.
 
 
 ## FAQ
@@ -39,9 +44,9 @@ Or, in Rails 7+, you can preconfigure your new application to use a specific bun
 
 The default build script for esbuild relies on the `app/javascript/*.*` glob pattern to compile multiple entrypoints automatically. This glob pattern is not available by default on Windows, so you need to change the build script in `package.json` to manually list the entrypoints you wish to compile.
 
-### Why does esbuild overwrite my application.css?
+### Why does bun/esbuild overwrite my application.css?
 
-If you [import CSS](https://esbuild.github.io/content-types/#css-from-js) in your application.js while using esbuild, you'll be creating both an `app/assets/builds/application.js` _and_ `app/assets/builds/application.css` file when bundling. The latter can conflict with the `app/assets/builds/application.css` produced by [cssbundling-rails](https://github.com/rails/cssbundling-rails). The solution is to either change the output file for esbuild (and the references for that) or for cssbundling. Both are specified in `package.json`. 
+If you [import CSS](https://esbuild.github.io/content-types/#css-from-js) in your application.js while using esbuild or Bun, you'll be creating both an `app/assets/builds/application.js` _and_ `app/assets/builds/application.css` file when bundling. The latter can conflict with the `app/assets/builds/application.css` produced by [cssbundling-rails](https://github.com/rails/cssbundling-rails). The solution is to either change the output file for bun/esbuild (and the references for that) or for cssbundling. Both are specified in `package.json`.
 
 ### How can I reference static assets in JavaScript code?
 

lib/install/bun/Procfile.dev

@@ -0,0 +1,2 @@
+web: env RUBY_DEBUG_OPEN=true bin/rails server
+js: bun run build --watch

lib/install/bun/bun.config.js

@@ -0,0 +1,37 @@
+import path from 'path';
+import fs from 'fs';
+
+const config = {
+  sourcemap: "external",
+  entrypoints: ["app/javascript/application.js"],
+  outdir: path.join(process.cwd(), "app/assets/builds"),
+};
+
+const build = async (config) => {
+  const result = await Bun.build(config);
+
+  if (!result.success) {
+    if (process.argv.includes('--watch')) {
+      console.error("Build failed");
+      for (const message of result.logs) {
+        console.error(message);
+      }
+      return;
+    } else {
+      throw new AggregateError(result.logs, "Build failed");
+    }
+  }
+};
+
+(async () => {
+  await build(config);
+
+  if (process.argv.includes('--watch')) {
+    fs.watch(path.join(process.cwd(), "app/javascript"), { recursive: true }, (eventType, filename) => {
+      console.log(`File changed: ${filename}. Rebuilding...`);
+      build(config);
+    });
+  } else {
+    process.exit(0);
+  }
+})();

lib/install/bun/install.rb

@@ -0,0 +1,20 @@
+require 'json'
+
+if Rails.root.join("Procfile.dev").exist?
+  append_to_file "Procfile.dev", "js: bun build --watch\n"
+else
+  say "Add default Procfile.dev"
+  copy_file "#{__dir__}/Procfile.dev", "Procfile.dev"
+
+  say "Ensure foreman is installed"
+  run "gem install foreman"
+end
+
+say "Add default bun.config.js"
+copy_file "#{__dir__}/bun.config.js", "bun.config.js"
+
+say "Add build script to package.json"
+package_json = JSON.parse(File.read("package.json"))
+package_json["scripts"] ||= {}
+package_json["scripts"]["build"] = "bun bun.config.js"
+File.write("package.json", JSON.pretty_generate(package_json))

lib/install/install.rb

@@ -31,16 +31,6 @@
   copy_file "#{__dir__}/package.json", "package.json"
 end
 
-if Rails.root.join("Procfile.dev").exist?
-  append_to_file "Procfile.dev", "js: yarn build --watch\n"
-else
-  say "Add default Procfile.dev"
-  copy_file "#{__dir__}/Procfile.dev", "Procfile.dev"
-
-  say "Ensure foreman is installed"
-  run "gem install foreman"
-end
-
 say "Add bin/dev to start foreman"
 copy_file "#{__dir__}/dev", "bin/dev"
 chmod "bin/dev", 0755, verbose: false

lib/install/install_node.rb

@@ -0,0 +1,9 @@
+if Rails.root.join("Procfile.dev").exist?
+  append_to_file "Procfile.dev", "js: yarn build --watch\n"
+else
+  say "Add default Procfile.dev"
+  copy_file "#{__dir__}/Procfile.dev", "Procfile.dev"
+
+  say "Ensure foreman is installed"
+  run "gem install foreman"
+end

lib/tasks/jsbundling/build.rake

@@ -1,18 +1,37 @@
 namespace :javascript do
   desc "Install JavaScript dependencies"
   task :install do
-    unless system "yarn install"
-      raise "jsbundling-rails: Command install failed, ensure yarn is installed"
+    command = install_command
+    unless system(command)
+      raise "jsbundling-rails: Command install failed, ensure #{command.split.first} is installed"
     end
   end
 
   desc "Build your JavaScript bundle"
   build_task = task :build do
-    unless system "yarn build"
-      raise "jsbundling-rails: Command build failed, ensure `yarn build` runs without errors"
+    command = build_command
+    unless system(command)
+      raise "jsbundling-rails: Command build failed, ensure `#{command}` runs without errors"
     end
   end
-  build_task.prereqs << :install unless ENV["SKIP_YARN_INSTALL"]
+
+  build_task.prereqs << :install unless ENV["SKIP_YARN_INSTALL"] || ENV["SKIP_BUN_INSTALL"]
+end
+
+def install_command
+  return "bun install" if File.exist?('bun.lockb') || (tool_exists?('bun') && !File.exist?('yarn.lock'))
+  return "yarn install" if File.exist?('yarn.lock') || tool_exists?('yarn')
+  raise "jsbundling-rails: No suitable tool found for installing JavaScript dependencies"
+end
+
+def build_command
+  return "bun run build" if File.exist?('bun.lockb') || (tool_exists?('bun') && !File.exist?('yarn.lock'))
+  return "yarn build" if File.exist?('yarn.lock') || tool_exists?('yarn')
+  raise "jsbundling-rails: No suitable tool found for building JavaScript"
+end
+
+def tool_exists?(tool)
+  system "command -v #{tool} > /dev/null"
 end
 
 unless ENV["SKIP_JS_BUILD"]

lib/tasks/jsbundling/install.rake

@@ -5,18 +5,28 @@ namespace :javascript do
       system "#{RbConfig.ruby} ./bin/rails app:template LOCATION=#{File.expand_path("../../install/install.rb",  __dir__)}"
     end
 
+    desc "Install node-specific elements for bundlers that use node/yarn."
+    task :node_shared do
+      system "#{RbConfig.ruby} ./bin/rails app:template LOCATION=#{File.expand_path("../../install/install_node.rb",  __dir__)}"
+    end
+
+    desc "Install Bun"
+    task bun: "javascript:install:shared" do
+      system "#{RbConfig.ruby} ./bin/rails app:template LOCATION=#{File.expand_path("../../install/bun/install.rb",  __dir__)}"
+    end
+
     desc "Install esbuild"
-    task esbuild: "javascript:install:shared" do
+    task esbuild: ["javascript:install:shared", "javascript:install:node_shared"] do
       system "#{RbConfig.ruby} ./bin/rails app:template LOCATION=#{File.expand_path("../../install/esbuild/install.rb",  __dir__)}"
     end
 
     desc "Install rollup.js"
-    task rollup: "javascript:install:shared" do
+    task rollup: ["javascript:install:shared", "javascript:install:node_shared"] do
       system "#{RbConfig.ruby} ./bin/rails app:template LOCATION=#{File.expand_path("../../install/rollup/install.rb",  __dir__)}"
     end
 
     desc "Install Webpack"
-    task webpack: "javascript:install:shared" do
+    task webpack: ["javascript:install:shared", "javascript:install:node_shared"] do
       system "#{RbConfig.ruby} ./bin/rails app:template LOCATION=#{File.expand_path("../../install/webpack/install.rb",  __dir__)}"
     end
   end