Add rack.response_finished to Rack::Lint

SPEC.rdoc

@@ -137,6 +137,14 @@ There are the following restrictions:
   set. <tt>PATH_INFO</tt> should be <tt>/</tt> if
   <tt>SCRIPT_NAME</tt> is empty.
   <tt>SCRIPT_NAME</tt> never should be <tt>/</tt>, but instead be empty.
+<tt>rack.response.finished</tt>:: An array of objects responding to #call with one argument, the env hash for the request, that will be called after the HTTP response has been sent to the client.
+The callables are called directly after the HTTP response has been sent to the
+client. The callables should be called sequentially and synchronously in the
+same execution context as the the response. If an exception is raised, it will
+be ignored and will not impact the execution of the other callables. The
+callbacks will be called event if the request is cancelled (e.g. a user closing
+the browser tab before the request completes). Servers supporting this
+functionality will prepopulate env with an empty array.
 
 === The Input Stream
 

lib/rack/constants.rb

@@ -52,6 +52,7 @@ module Rack
   RACK_RECURSIVE_INCLUDE              = 'rack.recursive.include'
   RACK_MULTIPART_BUFFER_SIZE          = 'rack.multipart.buffer_size'
   RACK_MULTIPART_TEMPFILE_FACTORY     = 'rack.multipart.tempfile_factory'
+  RACK_RESPONSE_FINISHED              = 'rack.response.finished'
   RACK_REQUEST_FORM_INPUT             = 'rack.request.form_input'
   RACK_REQUEST_FORM_HASH              = 'rack.request.form_hash'
   RACK_REQUEST_FORM_VARS              = 'rack.request.form_vars'

lib/rack/lint.rb

@@ -359,6 +359,23 @@ def check_environment(env)
         unless env[SCRIPT_NAME] != "/"
           raise LintError, "SCRIPT_NAME cannot be '/', make it '' and PATH_INFO '/'"
         end
+
+        ## <tt>rack.response.finished</tt>:: An array of callables run after the HTTP response has been sent.
+        if callables = env[RACK_RESPONSE_FINISHED]
+          raise LintError, "rack.response.finished must be an array of callable objects" unless callables.is_a?(Array)
+
+          callables.each do |callable|
+            raise LintError, "rack.response.finished values must respond to call" unless callable.respond_to?(:call)
+
+            arity = if callable.respond_to?(:arity)
+              callable.arity
+            else
+              callable.method(:call).arity
+            end
+
+            raise LintError, "rack.response.finished values must accept an env argument" unless arity == 1
+          end
+        end
       end
 
       ##

test/spec_lint.rb

@@ -209,6 +209,31 @@ def obj.error(*) end
       Rack::Lint.new(nil).call(env("SCRIPT_NAME" => "/"))
     }.must_raise(Rack::Lint::LintError).
       message.must_match(/cannot be .* make it ''/)
+
+    lambda {
+      Rack::Lint.new(nil).call(env("rack.response.finished" => "not a callable"))
+    }.must_raise(Rack::Lint::LintError).
+    message.must_match(/rack.response.finished must be an array of callable objects/)
+
+    lambda {
+      Rack::Lint.new(nil).call(env("rack.response.finished" => [-> (env) {}, "not a callable"]))
+    }.must_raise(Rack::Lint::LintError).
+    message.must_match(/rack.response.finished values must respond to call/)
+
+    lambda {
+      Rack::Lint.new(nil).call(env("rack.response.finished" => [-> () {}]))
+    }.must_raise(Rack::Lint::LintError).
+    message.must_match(/rack.response.finished values must accept an env argument/)
+
+    callable_object = Class.new do
+      def call
+      end
+    end.new
+
+    lambda {
+      Rack::Lint.new(nil).call(env("rack.response.finished" => [callable_object]))
+    }.must_raise(Rack::Lint::LintError).
+    message.must_match(/rack.response.finished values must accept an env argument/)
   end
 
   it "notice input errors" do
@@ -708,4 +733,15 @@ def assert_lint(*args)
                      }).call(env({}))[1]['rack.hijack'].call(StringIO.new).read.must_equal ''
   end
 
+  it "pass valid rack.response.finished" do
+    callable_object = Class.new do
+      def call(env)
+      end
+    end.new
+
+    Rack::Lint.new(lambda { |env|
+                     [200, {}, ["foo"]]
+                   }).call(env({ "rack.response.finished" => [-> (env) {}, lambda { |env| }, callable_object], "content-length" => "3" })).first.must_equal 200
+  end
+
 end