3 files changed, 29 insertions, 0 deletions
diff --git a/actionpack/CHANGELOG.md b/actionpack/CHANGELOG.md
index fd3f9eb72d..d4201e35b1 100644
--- a/actionpack/CHANGELOG.md
+++ b/actionpack/CHANGELOG.md
@@ -1,3 +1,10 @@
+*   Added verification of route constraints given as a Proc or an object responding
+    to `:matches?`.  Previously, when given an non-complying object, it would just
+    silently fail to enforce the constraint.  It will now raise an ArgumentError
+    when setting up the routes.
+
+    *Xavier Defrang*
+
 *   Properly treat the entire IPv6 User Local Address space as private for
     purposes of remote IP detection. Also handle uppercase private IPv6
     addresses.
diff --git a/actionpack/lib/action_dispatch/routing/mapper.rb b/actionpack/lib/action_dispatch/routing/mapper.rb
index 400956adee..6c4c7c8d80 100644
--- a/actionpack/lib/action_dispatch/routing/mapper.rb
+++ b/actionpack/lib/action_dispatch/routing/mapper.rb
@@ -159,6 +159,8 @@ module ActionDispatch
                   @defaults[key] ||= default
                 end
               end
+            elsif options[:constraints]
+              verify_callable_constraint(options[:constraints])
             end
 
             if Regexp === options[:format]
@@ -168,6 +170,11 @@ module ActionDispatch
             end
           end
 
+          def verify_callable_constraint(callable_constraint)
+            return if callable_constraint.respond_to?(:call) || callable_constraint.respond_to?(:matches?)
+            raise ArgumentError, "Invalid constraint: #{callable_constraint.inspect} must respond to :call or :matches?"
+          end
+
           def normalize_conditions!
             @conditions[:path_info] = path
 
diff --git a/actionpack/test/dispatch/routing_test.rb b/actionpack/test/dispatch/routing_test.rb
index b22a56bb27..52fc7b3243 100644
--- a/actionpack/test/dispatch/routing_test.rb
+++ b/actionpack/test/dispatch/routing_test.rb
@@ -4111,6 +4111,21 @@ class TestFormatConstraints < ActionDispatch::IntegrationTest
   end
 end
 
+class TestCallableConstraintValidation < ActionDispatch::IntegrationTest
+
+  def test_constraint_with_object_not_callable
+    assert_raise(ArgumentError) do
+      ActionDispatch::Routing::RouteSet.new.tap do |app|
+        app.draw do
+          ok = lambda { |env| [200, { 'Content-Type' => 'text/plain' }, []] }
+          get '/test', to: ok, constraints: Object.new
+        end
+      end
+    end
+  end
+
+end
+
 class TestRouteDefaults < ActionDispatch::IntegrationTest
   stub_controllers do |routes|
     Routes = routes