Strip unicode byte order mark from UTF8 config.ru

3 files changed, 10 insertions, 1 deletions

diff --git a/lib/rack/builder.rb b/lib/rack/builder.rb
index fc36b371..d1d07ff5 100644
--- a/lib/rack/builder.rb
+++ b/lib/rack/builder.rb
@@ -31,10 +31,13 @@ module Rack
   # You can use +map+ to construct a Rack::URLMap in a convenient way.
 
   class Builder
+    UTF_8_BOM = '\xef\xbb\xbf'
+
     def self.parse_file(config, opts = Server::Options.new)
       options = {}
       if config =~ /\.ru$/
         cfgfile = ::File.read(config)
+        cfgfile.slice!(/\A#{UTF_8_BOM}/) if cfgfile.encoding == Encoding::UTF_8
         if cfgfile[/^#\\(.*)/] && opts
           options = opts.parse! $1.split(/\s+/)
         end
diff --git a/test/builder/bom.ru b/test/builder/bom.ru
new file mode 100644
index 00000000..3f023393
--- /dev/null
+++ b/test/builder/bom.ru
@@ -0,0 +1 @@
+run -> (env) { [200, {'Content-Type' => 'text/plain'}, ['OK']] }
diff --git a/test/spec_builder.rb b/test/spec_builder.rb
index 40e602e8..66c7bf7f 100644
--- a/test/spec_builder.rb
+++ b/test/spec_builder.rb
@@ -199,7 +199,7 @@ describe Rack::Builder do
       end)
       o = Object.new
       def o.call(env)
-        @a = 1 if env['PATH_INFO'] == '/b'; 
+        @a = 1 if env['PATH_INFO'] == '/b';
         [200, {}, []]
       end
       run o
@@ -258,6 +258,11 @@ describe Rack::Builder do
       app, _ = Rack::Builder.parse_file config_file('line.ru')
       Rack::MockRequest.new(app).get("/").body.to_s.must_equal '1'
     end
+
+    it "strips leading unicode byte order mark when present" do
+      app, _ = Rack::Builder.parse_file config_file('bom.ru')
+      Rack::MockRequest.new(app).get("/").body.to_s.must_equal 'OK'
+    end
   end
 
   describe 'new_from_string' do