Use latest EmberCLI-generated asset files

Closes [#298]

Use Sprockets-generated manifest to detect which files are the most up
to date versions of EmberCLI-generated assets.

No longer support Sprockets-based helpers for Rails 3.2, given the
difference in how the Asset Pipeline works post-4.0.

[#298]: #298

CHANGELOG.md

@@ -1,9 +1,11 @@
 master
 ------
 
+* Use latest EmberCLI-generated asset files. [#316]
 * Delete previous build output on application boot instead of on process exit.
   [#308]
 
+[#316]: https://github.com/thoughtbot/ember-cli-rails/pull/316
 [#308]: https://github.com/thoughtbot/ember-cli-rails/pull/308
 
 0.5.6

README.md

@@ -198,6 +198,10 @@ In addition to rendering the EmberCLI generated `index.html`, you can inject the
 <%= include_ember_stylesheet_tags :frontend %>
 ```
 
+**NOTE**
+
+These helpers are only available for Rails versions `>= 4.0`.
+
 ### Multiple Ember CLI apps
 
 In the initializer you may specify multiple Ember CLI apps, each of which can be
@@ -519,10 +523,14 @@ jQuery and Handlebars are the main use cases for this flag.
 This project supports:
 
 * Ruby versions `>= 2.1.0`
-* Rails `3.2.x` and `>=4.1.x`.
+* Rails versions `3.2.x` and `>=4.1.x`.
+
+[Rendering EmberCLI-generated assets through Sprockets](asset-helpers) is
+**NOT** supported for Rails `3.2.x`.
 
 To learn more about supported versions and upgrades, read the [upgrading guide].
 
+[asset-helpers]: #rendering-the-embercli-generated-js-and-css
 [upgrading guide]: /UPGRADING.md
 
 ## Contributing

app/helpers/ember_rails_helper.rb

@@ -2,11 +2,7 @@
 
 module EmberRailsHelper
   def include_ember_index_html(name, &block)
-    warn <<-MSG.strip_heredoc
-      The `include_ember_index_html` helper has been deprecated.
-
-      Rename all invocations to `render_ember_app`
-    MSG
+    Warnings.warn_include_index_html
 
     render_ember_app(name, &block)
   end
@@ -20,10 +16,44 @@ def render_ember_app(name, &block)
   end
 
   def include_ember_script_tags(name, **options)
-    javascript_include_tag(*EmberCli[name].sprockets.assets, options)
+    Warnings.warn_asset_helper
+
+    javascript_include_tag(*EmberCli[name].sprockets.javascript_assets, options)
   end
 
   def include_ember_stylesheet_tags(name, **options)
-    stylesheet_link_tag(*EmberCli[name].sprockets.assets, options)
+    Warnings.warn_asset_helper
+
+    stylesheet_link_tag(*EmberCli[name].sprockets.stylesheet_assets, options)
+  end
+
+  module Warnings
+    def self.warn_include_index_html
+      warn <<-MSG.strip_heredoc
+        The `include_ember_index_html` helper has been deprecated.
+
+        Rename all invocations to `render_ember_app`
+      MSG
+    end
+
+    def self.warn_asset_helper
+      if Rails::VERSION::MAJOR < 4
+        warn <<-MSG.strip_heredoc
+          `ember-cli-rails` no longer supports Sprockets-based helpers for Rails
+          versions below 4.0.
+
+          Replace usage of
+            * `include_ember_script_tags`
+            * `include_ember_stylesheet_tags`
+
+          with `render_ember_app` invocations.
+
+          To learn more, please read:
+
+          * https://github.com/thoughtbot/ember-cli-rails#configuring-the-ember-controller
+          * https://github.com/thoughtbot/ember-cli-rails/pull/316
+        MSG
+      end
+    end
   end
 end

lib/ember_cli/assets.rb

@@ -0,0 +1,57 @@
+module EmberCli
+  class Assets
+    def initialize(app_name:, ember_app_name:, manifest:, prefix:)
+      @app_name = app_name
+      @ember_app_name = ember_app_name
+      @prefix = prefix
+      @manifest = manifest
+    end
+
+    def javascripts
+      if empty_manifest?
+        fallback_assets
+      else
+        [
+          latest_matching(%r{#{app_name}/assets/vendor(.*)\.js\z}),
+          latest_matching(%r{#{app_name}/assets/#{ember_app_name}(.*)\.js\z}),
+        ]
+      end
+    end
+
+    def stylesheets
+      if empty_manifest?
+        fallback_assets
+      else
+        [
+          latest_matching(%r{#{app_name}/assets/vendor(.*)\.css\z}),
+          latest_matching(%r{#{app_name}/assets/#{ember_app_name}(.*)\.css\z}),
+        ]
+      end
+    end
+
+    private
+
+    attr_reader :app_name, :ember_app_name, :manifest, :prefix
+
+    def fallback_assets
+      ["#{app_name}/assets/vendor", "#{app_name}/assets/#{ember_app_name}"]
+    end
+
+    def empty_manifest?
+      files.empty?
+    end
+
+    def latest_matching(regex)
+      file, = files.
+        select { |key, _| key =~ regex }.
+        sort_by { |_, data| data["mtime"] }.
+        last
+
+      [prefix, file].join("/")
+    end
+
+    def files
+      manifest.files
+    end
+  end
+end

lib/ember_cli/missing_manifest.rb

@@ -0,0 +1,11 @@
+module EmberCli
+  class MissingManifest
+    def files
+      {}
+    end
+
+    def assets
+      {}
+    end
+  end
+end

lib/ember_cli/sprockets.rb

@@ -1,16 +1,20 @@
+require "sprockets"
 require "ember_cli/errors"
 require "non-stupid-digest-assets"
 require "ember_cli/html_page"
+require "ember_cli/missing_manifest"
+require "ember_cli/assets"
 
 module EmberCli
   class Sprockets
     class AssetPipelineError < BuildError; end
+
     def initialize(app)
       @app = app
     end
 
     def register!
-      register_or_raise!(Rails.configuration.assets.precompile)
+      register_or_raise!(asset_config.precompile)
       register_or_raise!(NonStupidDigestAssets.whitelist)
     end
 
@@ -24,14 +28,27 @@ def index_html(head:, body:)
       html_page.render
     end
 
-    def assets
-      ["#{app.name}/assets/vendor", "#{app.name}/assets/#{ember_app_name}"]
+    def javascript_assets
+      assets.javascripts
+    end
+
+    def stylesheet_assets
+      assets.stylesheets
     end
 
     private
 
     attr_reader :app
 
+    def assets
+      Assets.new(
+        app_name: app.name,
+        ember_app_name: ember_app_name,
+        manifest: rails_manifest,
+        prefix: asset_config.prefix,
+      )
+    end
+
     def ember_app_name
       @ember_app_name ||= app.options.fetch(:name) { package_json.fetch(:name) }
     end
@@ -41,6 +58,18 @@ def package_json
         JSON.parse(app.paths.package_json_file.read).with_indifferent_access
     end
 
+    def rails_manifest
+      if Rails.application.respond_to?(:assets_manifest)
+        Rails.application.assets_manifest
+      else
+        MissingManifest.new
+      end
+    end
+
+    def asset_config
+      Rails.configuration.assets
+    end
+
     def asset_matcher
       %r{\A#{app.name}/}
     end

spec/lib/ember_cli/app_spec.rb

@@ -1,9 +1,17 @@
 require "ember-cli-rails"
 
 describe EmberCli::App do
+  describe "#compile" do
+    it "exits with exit status of 0" do
+      passed = EmberCli["my-app"].compile
+
+      expect(passed).to be true
+    end
+  end
+
   describe "#test" do
     it "exits with exit status of 0" do
-      passed = silence_stream(STDOUT) { EmberCli["my-app"].test }
+      passed = EmberCli["my-app"].test
 
       expect(passed).to be true
     end

spec/lib/ember_cli/assets_spec.rb

@@ -0,0 +1,103 @@
+require "ember_cli/assets"
+
+describe EmberCli::Assets do
+  describe "#javascripts" do
+    it "includes the most recent javascript build artifacts" do
+      manifest = build_manifest(
+        files: {
+          "not-a-match" => {},
+          "foo/assets/bar-abc123.js" => { "mtime" => 1.day.ago.iso8601 },
+          "foo/assets/bar-def456.js" => { "mtime" => 2.days.ago.iso8601 },
+          "foo/assets/vendor-def456.js" => { "mtime" => 2.days.ago.iso8601 },
+          "foo/assets/vendor-abc123.js" => { "mtime" => 1.day.ago.iso8601 },
+        },
+      )
+      assets = build_assets(
+        app_name: "foo",
+        ember_app_name: "bar",
+        manifest: manifest,
+        prefix: "assets",
+      )
+
+      javascripts = assets.javascripts
+
+      expect(javascripts).to match_array([
+        "assets/foo/assets/bar-abc123.js",
+        "assets/foo/assets/vendor-abc123.js",
+      ])
+    end
+
+    context "when the manifest is empty" do
+      it "falls back to the default assets" do
+        assets = build_assets(
+          manifest: build_empty_manifest,
+          app_name: "foo",
+          ember_app_name: "bar",
+        )
+
+        javascripts = assets.javascripts
+
+        expect(javascripts).to match_array([
+          "foo/assets/vendor",
+          "foo/assets/bar",
+        ])
+      end
+    end
+  end
+
+  describe "#stylesheets" do
+    it "includes the most recent stylesheet build artifacts" do
+      manifest = build_manifest(
+        files: {
+          "not-a-match" => {},
+          "foo/assets/bar-def456.css" => { "mtime" => 2.days.ago.iso8601 },
+          "foo/assets/bar-abc123.css" => { "mtime" => 1.day.ago.iso8601 },
+          "foo/assets/vendor-abc123.css" => { "mtime" => 1.day.ago.iso8601 },
+          "foo/assets/vendor-def456.css" => { "mtime" => 2.days.ago.iso8601 },
+        },
+      )
+      assets = build_assets(
+        app_name: "foo",
+        ember_app_name: "bar",
+        manifest: manifest,
+        prefix: "assets",
+      )
+
+      stylesheets = assets.stylesheets
+
+      expect(stylesheets).to match_array([
+        "assets/foo/assets/bar-abc123.css",
+        "assets/foo/assets/vendor-abc123.css",
+      ])
+    end
+
+    context "when the manifest is empty" do
+      it "falls back to the default assets" do
+        assets = build_assets(
+          manifest: build_empty_manifest,
+          app_name: "foo",
+          ember_app_name: "bar",
+        )
+
+        stylesheets = assets.stylesheets
+
+        expect(stylesheets).to match_array([
+          "foo/assets/vendor",
+          "foo/assets/bar",
+        ])
+      end
+    end
+  end
+end
+
+def build_assets(manifest: build_manifest, prefix: "assets", **options)
+  EmberCli::Assets.new(options.merge(manifest: manifest, prefix: prefix))
+end
+
+def build_manifest(files: {})
+  double(files: files)
+end
+
+def build_empty_manifest
+  build_manifest
+end