Set application/css-sourcemap+json charset to unicode

CHANGELOG.md

@@ -3,6 +3,7 @@
 Get upgrade notes from Sprockets 3.x to 4.x at https://github.com/rails/sprockets/blob/master/UPGRADING.md
 
 - Fix for precompile issues when multiple extensions map to the same MIME type (eg. `.jpeg` / `.jpg`). [#781](https://github.com/rails/sprockets/pull/781)
+- Fix `application/css-sourcemap+json` charset [#764](https://github.com/rails/sprockets/pull/764)
 
 ## 4.2.0
 

lib/sprockets.rb

@@ -91,7 +91,7 @@ module Sprockets
 
   require 'sprockets/source_map_processor'
   register_mime_type 'application/js-sourcemap+json', extensions: ['.js.map'], charset: :unicode
-  register_mime_type 'application/css-sourcemap+json', extensions: ['.css.map']
+  register_mime_type 'application/css-sourcemap+json', extensions: ['.css.map'], charset: :unicode
   register_transformer 'application/javascript', 'application/js-sourcemap+json', SourceMapProcessor
   register_transformer 'text/css', 'application/css-sourcemap+json', SourceMapProcessor
 

test/test_source_maps.rb

@@ -60,7 +60,7 @@ def get_sources(map)
     ], get_sources(map)
   end
 
-  test "reads the data transcoded to UTF-8" do
+  test "reads js data transcoded to UTF-8" do
     processor = Proc.new do |input|
       assert_equal Encoding::UTF_8, input[:data].encoding
       { data: input[:data] }
@@ -71,6 +71,17 @@ def get_sources(map)
     @env.unregister_preprocessor('application/javascript', processor)
   end
 
+  test "reads css data transcoded to UTF-8" do
+    processor = Proc.new do |input|
+      assert_equal Encoding::UTF_8, input[:data].encoding
+      { data: input[:data] }
+    end
+    @env.register_processor('text/css', processor)
+    assert asset = @env.find_asset('sass/precompiled/main.css', pipeline: :debug)
+  ensure
+    @env.unregister_preprocessor('text/css', processor)
+  end
+
   test "builds a minified source map" do
     @env.js_compressor = Sprockets::UglifierCompressor.new