1 files changed, 47 insertions, 0 deletions
diff --git a/actionpack/lib/action_dispatch/middleware/api_public_exceptions.rb b/actionpack/lib/action_dispatch/middleware/api_public_exceptions.rb
new file mode 100644
index 0000000000..126842672d
--- /dev/null
+++ b/actionpack/lib/action_dispatch/middleware/api_public_exceptions.rb
@@ -0,0 +1,47 @@
+module ActionDispatch
+  class ApiPublicExceptions
+    attr_accessor :public_path
+
+    def initialize(public_path)
+      @public_path = public_path
+    end
+
+    def call(env)
+      exception    = env["action_dispatch.exception"]
+      status       = env["PATH_INFO"][1..-1]
+      request      = ActionDispatch::Request.new(env)
+      content_type = request.formats.first
+      body         = { :status => status, :error => exception.message }
+
+      render(status, content_type, body)
+    end
+
+    private
+
+    def render(status, content_type, body)
+      format = content_type && "to_#{content_type.to_sym}"
+      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)
+      found = false
+      path = "#{public_path}/#{status}.#{I18n.locale}.html" if I18n.locale
+      path = "#{public_path}/#{status}.html" unless path && (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