Fail PersistentSequence if input port is not set (#5589)

* Fail if getInput fails

Signed-off-by: redvinaa <redvinaa@gmail.com>

* Add test with no input

Signed-off-by: redvinaa <redvinaa@gmail.com>

* Update error string

Co-authored-by: Steve Macenski <stevenmacenski@gmail.com>
Signed-off-by: Vince Reda <60265874+redvinaa@users.noreply.github.com>

* Fix quotation marks

Signed-off-by: redvinaa <redvinaa@gmail.com>

---------

Signed-off-by: redvinaa <redvinaa@gmail.com>
Signed-off-by: Vince Reda <60265874+redvinaa@users.noreply.github.com>
Co-authored-by: Steve Macenski <stevenmacenski@gmail.com>

Author: redvinaa

nav2_behavior_tree/plugins/control/persistent_sequence.cpp

@@ -29,7 +29,11 @@ BT::NodeStatus PersistentSequenceNode::tick()
   const int children_count = children_nodes_.size();
 
   int current_child_idx;
-  getInput("current_child_idx", current_child_idx);
+  if (!getInput("current_child_idx", current_child_idx)) {
+    throw BT::RuntimeError(
+      "Missing required input [current_child_idx] in PersistentSequenceNode. "
+      "Set via <Script code=\"current_child_idx := 0\" />");
+  }
 
   setStatus(BT::NodeStatus::RUNNING);
 

nav2_behavior_tree/test/plugins/control/test_persistent_sequence.cpp

@@ -62,6 +62,23 @@ std::shared_ptr<BT::BehaviorTreeFactory>
 PersistentSequenceTestFixture::factory_ = nullptr;
 std::shared_ptr<BT::Tree> PersistentSequenceTestFixture::tree_ = nullptr;
 
+TEST_F(PersistentSequenceTestFixture, test_empty_fails)
+{
+  // create tree
+  std::string xml_txt =
+    R"(
+      <root BTCPP_format="4">
+        <BehaviorTree ID="MainTree">
+          <PersistentSequence>
+            <AlwaysSuccess/>
+          </PersistentSequence>
+        </BehaviorTree>
+      </root>)";
+  tree_ = std::make_shared<BT::Tree>(factory_->createTreeFromText(xml_txt, config_->blackboard));
+
+  EXPECT_THROW(tree_->rootNode()->executeTick(), BT::RuntimeError);
+}
+
 TEST_F(PersistentSequenceTestFixture, test_tick)
 {
   // create tree