3 files changed, 58 insertions, 0 deletions
diff --git a/actionpack/CHANGELOG.md b/actionpack/CHANGELOG.md
index 2c1d544e4d..6bb1c63610 100644
--- a/actionpack/CHANGELOG.md
+++ b/actionpack/CHANGELOG.md
@@ -1,3 +1,10 @@
+*   Commit flash changes when using a redirect route.
+
+    Fixes #27992.
+
+    *Andrew White*
+
+
 ## Rails 5.1.0.beta1 (February 23, 2017) ##
 
 *   Prefer `remove_method` over `undef_method` when reloading routes
diff --git a/actionpack/lib/action_dispatch/routing/redirection.rb b/actionpack/lib/action_dispatch/routing/redirection.rb
index dabc045007..e8f47b8640 100644
--- a/actionpack/lib/action_dispatch/routing/redirection.rb
+++ b/actionpack/lib/action_dispatch/routing/redirection.rb
@@ -36,6 +36,8 @@ module ActionDispatch
         uri.host   ||= req.host
         uri.port   ||= req.port unless req.standard_port?
 
+        req.commit_flash
+
         body = %(<html><body>You are being <a href="#{ERB::Util.unwrapped_html_escape(uri.to_s)}">redirected</a>.</body></html>)
 
         headers = {
diff --git a/actionpack/test/dispatch/routing_test.rb b/actionpack/test/dispatch/routing_test.rb
index 53758a4fbc..d563df91df 100644
--- a/actionpack/test/dispatch/routing_test.rb
+++ b/actionpack/test/dispatch/routing_test.rb
@@ -4913,3 +4913,52 @@ class TestInternalRoutingParams < ActionDispatch::IntegrationTest
     )
   end
 end
+
+class FlashRedirectTest < ActionDispatch::IntegrationTest
+  SessionKey = "_myapp_session"
+  Generator  = ActiveSupport::LegacyKeyGenerator.new("b3c631c314c0bbca50c1b2843150fe33")
+
+  class KeyGeneratorMiddleware
+    def initialize(app)
+      @app = app
+    end
+
+    def call(env)
+      env["action_dispatch.key_generator"] ||= Generator
+      @app.call(env)
+    end
+  end
+
+  class FooController < ActionController::Base
+    def bar
+      render plain: (flash[:foo] || "foo")
+    end
+  end
+
+  Routes = ActionDispatch::Routing::RouteSet.new
+  Routes.draw do
+    get "/foo", to: redirect { |params, req| req.flash[:foo] = "bar"; "/bar" }
+    get "/bar", to: "flash_redirect_test/foo#bar"
+  end
+
+  APP = build_app Routes do |middleware|
+    middleware.use KeyGeneratorMiddleware
+    middleware.use ActionDispatch::Session::CookieStore, key: SessionKey
+    middleware.use ActionDispatch::Flash
+    middleware.delete ActionDispatch::ShowExceptions
+  end
+
+  def app
+    APP
+  end
+
+  include Routes.url_helpers
+
+  def test_block_redirect_commits_flash
+    get "/foo", env: { "action_dispatch.key_generator" => Generator }
+    assert_response :redirect
+
+    follow_redirect!
+    assert_equal "bar", response.body
+  end
+end