1 files changed, 57 insertions, 0 deletions
diff --git a/actionpack/lib/action_dispatch/middleware/public_exceptions.rb b/actionpack/lib/action_dispatch/middleware/public_exceptions.rb
new file mode 100644
index 0000000000..3feb3a19f3
--- /dev/null
+++ b/actionpack/lib/action_dispatch/middleware/public_exceptions.rb
@@ -0,0 +1,57 @@
+# frozen_string_literal: true
+
+module ActionDispatch
+  # When called, this middleware renders an error page. By default if an HTML
+  # response is expected it will render static error pages from the <tt>/public</tt>
+  # directory. For example when this middleware receives a 500 response it will
+  # render the template found in <tt>/public/500.html</tt>.
+  # If an internationalized locale is set, this middleware will attempt to render
+  # the template in <tt>/public/500.<locale>.html</tt>. If an internationalized template
+  # is not found it will fall back on <tt>/public/500.html</tt>.
+  #
+  # When a request with a content type other than HTML is made, this middleware
+  # will attempt to convert error information into the appropriate response type.
+  class PublicExceptions
+    attr_accessor :public_path
+
+    def initialize(public_path)
+      @public_path = public_path
+    end
+
+    def call(env)
+      request      = ActionDispatch::Request.new(env)
+      status       = request.path_info[1..-1].to_i
+      content_type = request.formats.first
+      body         = { status: status, error: Rack::Utils::HTTP_STATUS_CODES.fetch(status, Rack::Utils::HTTP_STATUS_CODES[500]) }
+
+      render(status, content_type, body)
+    end
+
+    private
+
+      def render(status, content_type, body)
+        format = "to_#{content_type.to_sym}" if content_type
+        if format && body.respond_to?(format)
+          render_format(status, content_type, body.public_send(format))
+        else
+          render_html(status)
+        end
+      end
+
+      def render_format(status, content_type, body)
+        [status, { "Content-Type" => "#{content_type}; charset=#{ActionDispatch::Response.default_charset}",
+                  "Content-Length" => body.bytesize.to_s }, [body]]
+      end
+
+      def render_html(status)
+        path = "#{public_path}/#{status}.#{I18n.locale}.html"
+        path = "#{public_path}/#{status}.html" unless (found = File.exist?(path))
+
+        if found || File.exist?(path)
+          render_format(status, "text/html", File.read(path))
+        else
+          [404, { "X-Cascade" => "pass" }, []]
+        end
+      end
+  end
+end