Add the possibility to remove a blackboard entry.

Add a node to use this functionality.

Signed-off-by: Gaël Écorchard <gael@km-robotics.cz>

Author: Gaël Écorchard

include/behaviortree_cpp/actions/set_blackboard_node.h

@@ -27,10 +27,10 @@ namespace BT
  *
  * Will store the string "42" in the entry with key "the_answer".
  */
-class SetBlackboard : public SyncActionNode
+class SetBlackboardNode : public SyncActionNode
 {
 public:
-  SetBlackboard(const std::string& name, const NodeConfig& config) :
+  SetBlackboardNode(const std::string& name, const NodeConfig& config) :
     SyncActionNode(name, config)
   {
     setRegistrationID("SetBlackboard");

include/behaviortree_cpp/actions/unset_blackboard_node.h

@@ -0,0 +1,48 @@
+/*  Copyright (C) 2018-2022 Davide Faconti, Eurecat -  All Rights Reserved
+*
+*   Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"),
+*   to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense,
+*   and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:
+*   The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.
+*
+*   THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+*   FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY,
+*   WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+*/
+
+#pragma once
+
+#include "behaviortree_cpp/action_node.h"
+
+namespace BT
+{
+/**
+ * Action that removes an entry from the blackboard and return SUCCESS.
+ */
+class UnsetBlackboardNode : public SyncActionNode
+{
+public:
+  UnsetBlackboardNode(const std::string& name, const NodeConfig& config) :
+    SyncActionNode(name, config)
+  {
+    setRegistrationID("UnsetBlackboard");
+  }
+
+  static PortsList providedPorts()
+  {
+    return { InputPort<std::string>("key", "Key of the entry to remove") };
+  }
+
+private:
+  virtual BT::NodeStatus tick() override
+  {
+    std::string key;
+    if (!getInput("key", key))
+    {
+      throw RuntimeError("missing input port [key]");
+    }
+    removeBlackboardEntry(key);
+    return NodeStatus::SUCCESS;
+  }
+};
+}   // namespace BT

include/behaviortree_cpp/behavior_tree.h

@@ -41,6 +41,7 @@
 #include "behaviortree_cpp/actions/set_blackboard_node.h"
 #include "behaviortree_cpp/actions/test_node.h"
 #include "behaviortree_cpp/actions/sleep_node.h"
+#include "behaviortree_cpp/actions/unset_blackboard_node.h"
 
 #include "behaviortree_cpp/decorators/force_success_node.h"
 #include "behaviortree_cpp/decorators/force_failure_node.h"

include/behaviortree_cpp/blackboard.h

@@ -199,7 +199,22 @@ class Blackboard
       new_value.copyInto(previous_any);
     }
   }
-  
+
+  void unset(const std::string& key)
+  {
+    std::unique_lock lock(mutex_);
+
+    // check local storage
+    auto it = storage_.find(key);
+    if (it == storage_.end())
+    {
+      // No entry, nothing to do.
+      return;
+    }
+
+    storage_.erase(it);
+  }
+
   [[nodiscard]] const TypeInfo* entryInfo(const std::string& key);
 
   void addSubtreeRemapping(StringView internal, StringView external);

include/behaviortree_cpp/tree_node.h

@@ -243,11 +243,18 @@ class TreeNode
    * @brief setOutput modifies the content of an Output port
    * @param key    the name of the port.
    * @param value  new value
-   * @return       valid Result, is succesfull.
+   * @return       valid Result, if succesful.
    */
   template <typename T>
   Result setOutput(const std::string& key, const T& value);
 
+  /**
+   * @brief removeBlackboardEntry erases an entry from the blackboard
+   * @param key    the name of the entry.
+   * @return       valid Result, if succesful.
+   */
+  Result removeBlackboardEntry(const std::string& key);
+
   /**
    * @brief getLockedPortContent should be used when:
    *
@@ -501,6 +508,18 @@ inline Result TreeNode::setOutput(const std::string& key, const T& value)
   return {};
 }
 
+inline Result TreeNode::removeBlackboardEntry(const std::string& key)
+{
+  if (!config().blackboard)
+  {
+    return nonstd::make_unexpected("setOutput() failed: trying to access a "
+                                   "Blackboard(BB) entry, but BB is invalid");
+  }
+
+  config().blackboard->unset(key);
+  return {};
+}
+
 // Utility function to fill the list of ports using T::providedPorts();
 template <typename T>
 inline void assignDefaultRemapping(NodeConfig& config)

src/bt_factory.cpp

@@ -78,8 +78,9 @@ BehaviorTreeFactory::BehaviorTreeFactory():
   registerNodeType<AlwaysFailureNode>("AlwaysFailure");
   registerNodeType<ScriptNode>("Script");
   registerNodeType<ScriptCondition>("ScriptCondition");
-  registerNodeType<SetBlackboard>("SetBlackboard");
+  registerNodeType<SetBlackboardNode>("SetBlackboard");
   registerNodeType<SleepNode>("Sleep");
+  registerNodeType<UnsetBlackboardNode>("UnsetBlackboard");
 
   registerNodeType<SubTreeNode>("SubTree");
 

src/xml_parsing.cpp

@@ -437,8 +437,13 @@ void VerifyXML(const std::string& xml_text,
     {
       if (children_count == 0)
       {
-        ThrowError(node->GetLineNum(), "A Control node must have at least 1 "
-                                       "child");
+        std::string name_attr;
+        if (node->Attribute("name"))
+        {
+          name_attr = "(`" + std::string(node->Attribute("name")) + "`)";
+        }
+        ThrowError(node->GetLineNum(), std::string("A Control node must have at least 1 "
+                                       "child, error in XML node `") + node->Name() + name_attr + "`");
       }
     }
     else if (name == "SubTree")