6 files changed, 44 insertions, 10 deletions
diff --git a/actionpack/README.rdoc b/actionpack/README.rdoc
index f56230ffa0..fe85bc5b7a 100644
--- a/actionpack/README.rdoc
+++ b/actionpack/README.rdoc
@@ -23,6 +23,7 @@ by default and Action View rendering is implicitly triggered by Action
 Controller. However, these modules are designed to function on their own and
 can be used outside of Rails.
 
+You can read more about Action Pack in the {Action Controller Overview}[https://guides.rubyonrails.org/action_controller_overview.html] guide.
 
 == Download and installation
 
@@ -46,7 +47,7 @@ Action Pack is released under the MIT license:
 
 API documentation is at:
 
-* http://api.rubyonrails.org
+* https://api.rubyonrails.org
 
 Bug reports for the Ruby on Rails project can be filed here:
 
diff --git a/actionpack/actionpack.gemspec b/actionpack/actionpack.gemspec
index c4c755b7ac..735eb734d0 100644
--- a/actionpack/actionpack.gemspec
+++ b/actionpack/actionpack.gemspec
@@ -15,7 +15,7 @@ Gem::Specification.new do |s|
 
   s.author   = "David Heinemeier Hansson"
   s.email    = "david@loudthinking.com"
-  s.homepage = "http://rubyonrails.org"
+  s.homepage = "https://rubyonrails.org"
 
   s.files        = Dir["CHANGELOG.md", "README.rdoc", "MIT-LICENSE", "lib/**/*"]
   s.require_path = "lib"
diff --git a/actionpack/lib/action_controller/metal.rb b/actionpack/lib/action_controller/metal.rb
index f875aa5e6b..b9088e6d86 100644
--- a/actionpack/lib/action_controller/metal.rb
+++ b/actionpack/lib/action_controller/metal.rb
@@ -26,10 +26,10 @@ module ActionController
       end
     end
 
-    def build(action, app = Proc.new)
+    def build(action, app = nil, &block)
       action = action.to_s
 
-      middlewares.reverse.inject(app) do |a, middleware|
+      middlewares.reverse.inject(app || block) do |a, middleware|
         middleware.valid?(action) ? middleware.build(a) : a
       end
     end
diff --git a/actionpack/lib/action_dispatch/http/response.rb b/actionpack/lib/action_dispatch/http/response.rb
index 1d38942a31..69798f99e0 100644
--- a/actionpack/lib/action_dispatch/http/response.rb
+++ b/actionpack/lib/action_dispatch/http/response.rb
@@ -82,6 +82,7 @@ module ActionDispatch # :nodoc:
     SET_COOKIE   = "Set-Cookie"
     LOCATION     = "Location"
     NO_CONTENT_CODES = [100, 101, 102, 204, 205, 304]
+    CONTENT_TYPE_PARSER = /\A(?<type>[^;\s]+)?(?:.*;\s*charset=(?<quote>"?)(?<charset>[^;\s]+)\k<quote>)?/ # :nodoc:
 
     cattr_accessor :default_charset, default: "utf-8"
     cattr_accessor :default_headers
@@ -409,10 +410,8 @@ module ActionDispatch # :nodoc:
     NullContentTypeHeader = ContentTypeHeader.new nil, nil
 
     def parse_content_type(content_type)
-      if content_type
-        type, charset = content_type.split(/;\s*charset=/)
-        type = nil if type && type.empty?
-        ContentTypeHeader.new(type, charset)
+      if content_type && match = CONTENT_TYPE_PARSER.match(content_type)
+        ContentTypeHeader.new(match[:type], match[:charset])
       else
         NullContentTypeHeader
       end
diff --git a/actionpack/lib/action_dispatch/middleware/stack.rb b/actionpack/lib/action_dispatch/middleware/stack.rb
index b82f8aa3a3..7a2fcd6db7 100644
--- a/actionpack/lib/action_dispatch/middleware/stack.rb
+++ b/actionpack/lib/action_dispatch/middleware/stack.rb
@@ -97,8 +97,8 @@ module ActionDispatch
       middlewares.push(build_middleware(klass, args, block))
     end
 
-    def build(app = Proc.new)
-      middlewares.freeze.reverse.inject(app) { |a, e| e.build(a) }
+    def build(app = nil, &block)
+      middlewares.freeze.reverse.inject(app || block) { |a, e| e.build(a) }
     end
 
     private
diff --git a/actionpack/test/dispatch/response_test.rb b/actionpack/test/dispatch/response_test.rb
index 60817c1c4d..7758b0406a 100644
--- a/actionpack/test/dispatch/response_test.rb
+++ b/actionpack/test/dispatch/response_test.rb
@@ -539,4 +539,38 @@ class ResponseIntegrationTest < ActionDispatch::IntegrationTest
     assert_equal('"202cb962ac59075b964b07152d234b70"', @response.headers["ETag"])
     assert_equal('"202cb962ac59075b964b07152d234b70"', @response.etag)
   end
+
+  test "response Content-Type with optional parameters" do
+    @app = lambda { |env|
+      [
+        200,
+        { "Content-Type" => "text/csv; charset=utf-16; header=present" },
+        ["Hello"]
+      ]
+    }
+
+    get "/"
+    assert_response :success
+
+    assert_equal("text/csv; charset=utf-16; header=present", @response.headers["Content-Type"])
+    assert_equal("text/csv", @response.content_type)
+    assert_equal("utf-16", @response.charset)
+  end
+
+  test "response Content-Type with quoted-string" do
+    @app = lambda { |env|
+      [
+        200,
+        { "Content-Type" => 'text/csv; header=present; charset="utf-16"' },
+        ["Hello"]
+      ]
+    }
+
+    get "/"
+    assert_response :success
+
+    assert_equal('text/csv; header=present; charset="utf-16"', @response.headers["Content-Type"])
+    assert_equal("text/csv", @response.content_type)
+    assert_equal("utf-16", @response.charset)
+  end
 end