Define custom cache resolvers for AC config

Author: josh

lib/sprockets/rails/context.rb

@@ -14,6 +14,8 @@ def self.included(klass)
       end
 
       def compute_asset_path(path, options = {})
+        @dependencies << 'actioncontroller-asset-url-config'
+
         begin
           asset_uri = resolve(path, compat: false)
         rescue FileNotFound
@@ -32,4 +34,10 @@ def compute_asset_path(path, options = {})
       end
     end
   end
+
+  register_dependency_resolver 'actioncontroller-asset-url-config' do |env|
+    config = env.context_class.config
+    [config.relative_url_root,
+    (config.asset_host unless config.asset_host.respond_to?(:call))]
+  end
 end

lib/sprockets/railtie.rb

@@ -88,16 +88,15 @@ def configure(&block)
       )
     end
 
+    Sprockets.register_dependency_resolver 'rails-env' do
+      ::Rails.env
+    end
+    config.assets.configure do |env|
+      env.depend_on 'environment-version'
+    end
+
     config.assets.configure do |env|
-      # Configuration options that should invalidate
-      # the Sprockets cache when changed.
-      env.version = [
-        ::Rails.env,
-        config.assets.version,
-        config.action_controller.relative_url_root,
-        (config.action_controller.asset_host unless config.action_controller.asset_host.respond_to?(:call)),
-        Sprockets::Rails::VERSION
-      ].compact.join('-')
+      env.version = config.assets.version
     end
 
     rake_tasks do |app|

test/test_railtie.rb

@@ -59,7 +59,7 @@ def test_defaults
     assert_kind_of Sprockets::Environment, env
 
     assert_equal ROOT, env.root
-    assert_equal "test--#{Sprockets::Rails::VERSION}", env.version
+    assert_equal "", env.version
     assert env.cache
     assert_equal [], env.paths
     assert_nil env.js_compressor
@@ -145,33 +145,7 @@ def test_version
     app.initialize!
 
     assert env = app.assets
-    assert_equal "test-v2-#{Sprockets::Rails::VERSION}", env.version
-  end
-
-  def test_version_fragments_with_string_asset_host
-    app.configure do
-      config.assets.version = 'v2'
-      config.action_controller.asset_host = 'http://some-cdn.com'
-      config.action_controller.relative_url_root = 'some-path'
-    end
-    app.initialize!
-
-    assert env = app.assets
-    assert_equal "test-v2-some-path-http://some-cdn.com-#{Sprockets::Rails::VERSION}", env.version
-  end
-
-  def test_version_fragments_with_proc_asset_host
-    app.configure do
-      config.assets.version = 'v2'
-      config.action_controller.asset_host = ->(path, request) {
-        'http://some-cdn.com'
-      }
-      config.action_controller.relative_url_root = 'some-path'
-    end
-    app.initialize!
-
-    assert env = app.assets
-    assert_equal "test-v2-some-path-#{Sprockets::Rails::VERSION}", env.version
+    assert_equal "v2", env.version
   end
 
   def test_configure