feat(routing): Expose native search limit check

README.md

@@ -1485,6 +1485,9 @@ assignment = routing.read_assignment_from_routes(routes, true)
 The limit is checked cooperatively, so the call can exceed it. Restoration can
 return a valid assignment found before the limit. A `nil` result does not
 distinguish an invalid route from a limit reached before finding a solution.
+Call `routing.check_limit` immediately after restoration to check whether the
+native search limit was reached. It returns a boolean, like Python's
+`routing.CheckLimit()`.
 A subsequent solve uses the time limit in its own search parameters.
 
 Native improvement-rate stopping is available through search parameters:

ext/or-tools/routing.cpp

@@ -865,6 +865,7 @@ void init_routing(Rice::Module& m) {
           self.CloseModel();
         }
       })
+    .define_method("check_limit", [](RoutingModel& self) { return self.CheckLimit(); })
     .define_method(
       "update_time_limit",
       [](RoutingModel& self, double seconds) {

test/routing_time_limit_test.rb

@@ -8,13 +8,26 @@ def test_restoration_limit_can_be_reset_after_timeout
 
     assert_nil routing.read_assignment_from_routes([[1, 2]], true)
     assert_equal :fail, routing.status
+    assert_equal true, routing.check_limit
 
     routing.update_time_limit(0.5)
     assignment = routing.read_assignment_from_routes([[1, 2]], true)
 
     refute_nil assignment
     assert_equal 4, assignment.objective_value
     assert_equal :success, routing.status
+    assert_equal false, routing.check_limit
+  end
+
+  def test_infeasible_restoration_does_not_cross_limit
+    routing = build_routing
+    transit = routing.register_transit_matrix([[0, 1, 2], [1, 0, 1], [2, 1, 0]])
+    routing.add_dimension(transit, 0, 3, true, "Distance")
+    routing.close_model
+    routing.update_time_limit(1)
+
+    assert_nil routing.read_assignment_from_routes([[1, 2]], true)
+    assert_equal false, routing.check_limit
   end
 
   def test_solve_replaces_restoration_time_limit