Own the interpretation of an application's build output

README.md

@@ -568,8 +568,14 @@ end
 Rendering EmberCLI applications with `render_ember_app` is the recommended,
 actively supported method of serving EmberCLI applications.
 
-However, for the sake of backwards compatibility, `ember-cli-rails` supports
-injecting the EmberCLI-generated assets into an existing Rails layout.
+However, for the sake of backwards compatibility, the EmberCLI-generated assets
+can be injected into an existing Rails layout.
+The helpers that do that ship in [ember-cli-rails-assets], so add it to the
+`Gemfile` alongside this gem:
+
+```ruby
+gem "ember-cli-rails-assets"
+```
 
 **Note:** for Vite-based applications (generated with `ember-cli >= 6.8`),
 use `include_ember_script_tags` on its own. It emits everything the

UPGRADING.md

@@ -1,48 +1,58 @@
+# Asset helpers
+
+From `ember-cli-rails@1.0.0` and on, the asset helpers are no longer installed alongside this gem.
+
+`ember-cli-rails` interprets a built Ember application and serves it; `ember-cli-rails-assets` renders what it reports into an existing Rails layout.
+Those are separate jobs, and this gem no longer depends on the other to do them, so an application that renders `include_ember_script_tags` or `include_ember_stylesheet_tags` has to ask for the helpers itself:
+
+```ruby
+# Gemfile
+
+gem "ember-cli-rails"
+gem "ember-cli-rails-assets"
+```
+
+Without that line the helpers are undefined, and rendering a layout that calls one fails with the `ActionView::Template::Error` raised from its `NoMethodError`.
+Everything else keeps working, so only the layouts that call the helpers break.
+
+An application that serves its Ember applications with `render_ember_app`, or mounts them with `mount_ember_app`, needs no change.
+That is the recommended way to serve an EmberCLI application, and it has never involved the helpers.
+
+The helpers used to work out for themselves what a built application boots from.
+`ember-cli-rails` reports that now, through `EmberCli::Embedding`, which wraps an application (`EmberCli::Embedding.new(EmberCli["frontend"])`) to embed it into a page of your own.
+Code that called into the helpers' internals calls this gem instead:
+
+* `EmberCli::Assets::Paths#vite?` is `EmberCli::App#vite?`
+* `EmberCli::Assets::Lookup#javascript_assets` and `#stylesheet_assets` are `EmberCli::Embedding#javascript_assets` and `#stylesheet_assets`, which take the `prepend:` the helpers used to join on themselves, and join it only onto the assets that point into the build
+* `EmberCli::Assets::AssetMap`, `EmberCli::Assets::DirectoryAssetMap` and `EmberCli::Assets::Url` have no replacement: `EmberCli::Embedding` reads the build with classes it keeps to itself
+* `EmberCli::Assets::BuildError` is `EmberCli::BuildError`, so rescue that instead
+
 # EmberCLI support
 
-`ember-cli >= 6.8` generates applications that are built with [Vite] instead
-of the classic Broccoli-based pipeline. `ember-cli-rails` supports both build
-systems, and detects the Vite-based build by the presence of a `vite.config.*`
-file in the Ember application's root.
-
-When upgrading an Ember application to the Vite-based blueprint, note the
-following differences in how `ember-cli-rails` treats it:
-
-* Remove `ember-cli-rails-addon` from the application's `package.json`. The
-  addon is incompatible with the Vite-based build (it forces
-  `storeConfigInMeta` off and ships an initializer that imports the removed
-  `ember` module), and `ember-cli-rails` no longer needs it there.
-* Use `include_ember_script_tags` on its own instead of pairing it with
-  `include_ember_stylesheet_tags`: for Vite-based applications it emits the
-  configuration meta tag, the stylesheet links, and the module script tags
-  all together, while `include_ember_stylesheet_tags` supports only classic
-  applications. This requires `ember-cli-rails-assets >= 0.9.0`.
-* In development, the application is served by Vite's development server —
-  the same one the application's `npm start` script runs. `ember-cli-rails`
-  starts it on the first request and shuts it down when Rails exits, and
-  rewrites the URLs in the `index.html` it serves so that the browser loads
-  the application's modules, and Vite's HMR client, from it directly. Changes
-  are hot-reloaded without restarting Rails.
-
-  The development server is the default — and the recommended — way to
-  develop a Vite-based application, and needs no configuration. When
-  configuring it anyway, a fixed `port` lets several Rails workers (or a
-  hand-started `npm start`) share a single server, and a longer `timeout`
-  accommodates a slow first boot:
+`ember-cli >= 6.8` generates applications that are built with [Vite] instead of the classic Broccoli-based pipeline.
+`ember-cli-rails` supports both build systems, and detects the Vite-based build by the presence of a `vite.config.*` file in the Ember application's root.
+
+When upgrading an Ember application to the Vite-based blueprint, note the following differences in how `ember-cli-rails` treats it:
+
+* Remove `ember-cli-rails-addon` from the application's `package.json`.
+  The addon is incompatible with the Vite-based build (it forces `storeConfigInMeta` off and ships an initializer that imports the removed `ember` module), and `ember-cli-rails` no longer needs it there.
+* Use `include_ember_script_tags` on its own instead of pairing it with `include_ember_stylesheet_tags`: for Vite-based applications it emits the configuration meta tag, the stylesheet links, and the module script tags all together, while `include_ember_stylesheet_tags` supports only classic applications.
+  This requires `ember-cli-rails-assets >= 0.9.0`.
+* In development, the application is served by Vite's development server — the same one the application's `npm start` script runs.
+  `ember-cli-rails` starts it on the first request and shuts it down when Rails exits, and rewrites the URLs in the `index.html` it serves so that the browser loads the application's modules, and Vite's HMR client, from it directly.
+  Changes are hot-reloaded without restarting Rails.
+
+  The development server is the default — and the recommended — way to develop a Vite-based application, and needs no configuration.
+  When configuring it anyway, a fixed `port` lets several Rails workers (or a hand-started `npm start`) share a single server, and a longer `timeout` accommodates a slow first boot:
 
   ```rb
   EmberCli.configure do |c|
     c.app :frontend, dev_server: { port: 4200, timeout: 120 }
   end
   ```
 
-  When Rails runs in a container and the browser outside of it, bind the
-  development server to every interface and name the browser-facing origin
-  separately: `dev_server: { host: "0.0.0.0", port: 4200, origin:
-  "http://localhost:4200" }`.
-  Opening the page on a LAN IP or a custom domain also needs `server.cors`
-  configured in `vite.config.*` — Vite's default allows localhost origins
-  only.
+  When Rails runs in a container and the browser outside of it, bind the development server to every interface and name the browser-facing origin separately: `dev_server: { host: "0.0.0.0", port: 4200, origin: "http://localhost:4200" }`.
+  Opening the page on a LAN IP or a custom domain also needs `server.cors` configured in `vite.config.*` — Vite's default allows localhost origins only.
 
   To opt out of the development server, disable it:
 
@@ -53,32 +63,24 @@ following differences in how `ember-cli-rails` treats it:
   end
   ```
 
-* `include_ember_script_tags` serves its startup tags from the development
-  server, with absolute URLs pointing at it — nothing is built, and changes
-  are picked up by reloading the page. With `dev_server: false` it reads the
-  output of `ember build` instead, built once, synchronously, on the first
-  request; restart the Rails server to pick up changes.
+* `include_ember_script_tags` serves its startup tags from the development server, with absolute URLs pointing at it — nothing is built, and changes are picked up by reloading the page.
+  With `dev_server: false` it reads the output of `ember build` instead, built once, synchronously, on the first request; restart the Rails server to pick up changes.
 
 [Vite]: https://vitejs.dev
 
 # Ruby support
 
-According to [these release notes][latest-eol], Ruby versions prior to `2.5.x`
-has been end-of-lifed.
+According to [these release notes][latest-eol], Ruby versions prior to `2.5.x` has been end-of-lifed.
 
 Additionally, this codebase makes use of [(required) keyword arguments][kwargs].
 
-From `ember-cli-rails@0.4.0` and on, we will no longer support versions of Ruby
-prior to `2.1.0`.
+From `ember-cli-rails@0.4.0` and on, we will no longer support versions of Ruby prior to `2.1.0`.
 
-`ember-cli-rails@0.8.0` adds support for Rails 5, which depends on `rack@2.0.x`,
-which **requires** Ruby `2.2.2` or greater.
+`ember-cli-rails@0.8.0` adds support for Rails 5, which depends on `rack@2.0.x`, which **requires** Ruby `2.2.2` or greater.
 
-From `ember-cli-rails@0.8.0` and on, we will no longer support versions of Ruby
-prior to `2.2.2`.
+From `ember-cli-rails@0.8.0` and on, we will no longer support versions of Ruby prior to `2.2.2`.
 
-From `ember-cli-rails@0.12.0` and on, we will no longer support versions of Ruby
-prior to `2.5.x`.
+From `ember-cli-rails@0.12.0` and on, we will no longer support versions of Ruby prior to `2.5.x`.
 
 To use `ember-cli-rails` with older versions of Ruby, try the `0.3.x` series.
 
@@ -87,15 +89,12 @@ To use `ember-cli-rails` with older versions of Ruby, try the `0.3.x` series.
 
 # Rails support
 
-According to the [Rails Maintenance Policy][version-policy], Rails versions
-prior to `5.2.x` have been end-of-lifed. Additionally, the `4.0.x` series no
-longer receives bug fixes of any sort.
+According to the [Rails Maintenance Policy][version-policy], Rails versions prior to `5.2.x` have been end-of-lifed.
+Additionally, the `4.0.x` series no longer receives bug fixes of any sort.
 
-From `ember-cli-rails@0.4.0` and on, we will no longer support versions of Rails
-prior to `3.2.0`, nor will we support the `4.0.x` series of releases.
+From `ember-cli-rails@0.4.0` and on, we will no longer support versions of Rails prior to `3.2.0`, nor will we support the `4.0.x` series of releases.
 
-From `ember-cli-rails@0.12.0` and on, we will no longer support versions of
-Rails prior to `5.2.0`.
+From `ember-cli-rails@0.12.0` and on, we will no longer support versions of Rails prior to `5.2.0`.
 
 To use `ember-cli-rails` with older versions of Rails, try the `0.3.x` series.
 

ember-cli-rails.gemspec

@@ -15,7 +15,7 @@ Gem::Specification.new do |spec|
 
   spec.required_ruby_version = ">= 2.5.0"
 
-  spec.add_dependency "ember-cli-rails-assets", ">= 0.9.0", "< 1.0"
+  spec.add_dependency "nokogiri", ">= 1.13"
   spec.add_dependency "railties", ">= 4.2"
   spec.add_dependency "rack", ">= 2.1", "< 4.0"
   spec.add_dependency "terrapin", ">= 0.6.0", "< 2.0"

lib/ember_cli.rb

@@ -1,9 +1,9 @@
 require "fileutils"
 require "active_support/deprecation"
-require "ember-cli-rails-assets"
 require "ember_cli/engine"
 require "ember_cli/configuration"
 require "ember_cli/helpers"
+require "ember_cli/embedding"
 require "ember_cli/errors"
 
 module EmberCli

lib/ember_cli/app.rb

@@ -75,6 +75,10 @@ def index_html(head:, body:, mount_point: nil)
       html.render
     end
 
+    def vite?
+      paths.vite?
+    end
+
     def install_dependencies
       @shell.install
     end

lib/ember_cli/embedding.rb

@@ -0,0 +1,49 @@
+require "ember_cli/embedding/asset_map"
+require "ember_cli/embedding/startup_tags"
+require "ember_cli/embedding/url"
+
+module EmberCli
+  class Embedding
+    private_constant :AssetMap, :StartupTags, :Url
+
+    def initialize(app)
+      @app = app
+    end
+
+    def startup_tags?
+      app.dev_server? || app.vite?
+    end
+
+    def startup_tags(prepend: "")
+      if app.dev_server?
+        StartupTags.new(app.dev_server.index_html, prefix: app.dev_server.origin).to_a
+      else
+        StartupTags.new(index_html.read, prefix: prepend).to_a
+      end
+    end
+
+    def javascript_assets(prepend: "")
+      asset_map.javascripts(prepend: prepend)
+    end
+
+    def stylesheet_assets(prepend: "")
+      asset_map.stylesheets(prepend: prepend)
+    end
+
+    private
+
+    attr_reader :app
+
+    def asset_map
+      AssetMap.new(
+        name: app.name,
+        index_html: index_html,
+        assets_path: app.dist_path.join("assets"),
+      )
+    end
+
+    def index_html
+      app.dist_path.join("index.html")
+    end
+  end
+end

lib/ember_cli/embedding/asset_map.rb

@@ -0,0 +1,92 @@
+require "nokogiri"
+
+require "ember_cli/errors"
+require "ember_cli/embedding/url"
+
+module EmberCli
+  class Embedding
+    class AssetMap
+      PREPEND = "assets/".freeze
+
+      def initialize(name:, index_html:, assets_path:)
+        @name = name
+        @index_html = index_html
+        @assets_path = assets_path
+      end
+
+      def javascripts(prepend: "")
+        assets_referenced_by("script", "src", prepend)
+      end
+
+      def stylesheets(prepend: "")
+        assets_referenced_by(%{link[rel="stylesheet"]}, "href", prepend)
+      end
+
+      private
+
+      attr_reader :name, :index_html, :assets_path
+
+      def assets_referenced_by(selector, attribute, prepend)
+        assert_built!
+
+        document.css(selector).filter_map do |tag|
+          asset_for(tag[attribute], prepend)
+        end
+      end
+
+      def document
+        @document ||= Nokogiri::HTML(index_html.read)
+      end
+
+      def asset_for(url, prepend)
+        if url.to_s.empty?
+          nil
+        elsif Url.remote?(url)
+          url
+        else
+          [prepend, asset_matching(url)].join
+        end
+      end
+
+      # A reference carries directories the build output does not, such as the
+      # `assets` directory itself or the application's `rootURL`, so match on the
+      # longest trailing path the two agree on rather than on the file name, which
+      # an addon's nested asset can share with another file.
+      def asset_matching(url)
+        asset = path_suffixes(url).find { |suffix| file_paths.include?(suffix) }
+
+        unless asset
+          fail BuildError, "Failed to find a built asset matching `#{url}`"
+        end
+
+        PREPEND + asset
+      end
+
+      def path_suffixes(url)
+        segments = url.split("/").reject(&:empty?)
+
+        segments.each_index.map { |index| segments[index..].join("/") }
+      end
+
+      def file_paths
+        @file_paths ||= if assets_path.directory?
+                          assets_path.glob("**/*", File::FNM_DOTMATCH).
+                            select(&:file?).
+                            map { |path| path.relative_path_from(assets_path).to_s }
+                        else
+                          []
+                        end
+      end
+
+      def assert_built!
+        if file_paths.empty?
+          fail BuildError, <<~MSG
+            Missing built assets for #{name.inspect} in `#{assets_path}`.
+
+            Build the application before rendering its assets.
+          MSG
+        end
+      end
+    end
+  end
+end

lib/ember_cli/embedding/startup_tags.rb

@@ -0,0 +1,45 @@
+require "nokogiri"
+
+require "ember_cli/embedding/url"
+
+module EmberCli
+  class Embedding
+    class StartupTags
+      SELECTOR = [
+        %{meta[name$="/config/environment"]},
+        %{link[rel="stylesheet"]},
+        %{link[rel="modulepreload"]},
+        "script",
+      ].join(", ").freeze
+
+      URL_ATTRIBUTES = %w(href src).freeze
+
+      def initialize(html, prefix: "")
+        @html = html
+        @prefix = prefix.to_s.chomp("/")
+      end
+
+      def to_a
+        Nokogiri::HTML5(html).css(SELECTOR).map { |tag| prefix_urls(tag).to_html }
+      end
+
+      private
+
+      attr_reader :html, :prefix
+
+      # Only a root-relative URL points into what this application serves, so a
+      # URL that resolves elsewhere is left alone.
+      def prefix_urls(tag)
+        URL_ATTRIBUTES.each do |attribute|
+          value = tag[attribute]
+
+          if value&.start_with?("/") && !Url.remote?(value)
+            tag[attribute] = "#{prefix}#{value}"
+          end
+        end
+
+        tag
+      end
+    end
+  end
+end