Add conditional

CHANGELOG.rst

@@ -1,6 +1,11 @@
 Changelog for package py_trees_parser
 
 .. This is only a rough description of the main changes of the repository
+0.6.1 (2025-03-21)
+------------------
+* Add inline argument substitution
+* Add conditionals
+
 0.6.0 (2025-01-24)
 ------------------
 * Split py_trees_parser out into its own repo

README.md

@@ -216,6 +216,21 @@ and finally in subtree2
 </py_trees.composites.Sequence>
 ```
 
+### Conditionals
+
+A conditionals allows one to choose which xml nodes should be included in the
+final tree. If a condition evaluates to true then the element is included in the
+final tree otherwise it is not. Conditionals can be used with any element of a
+behavior tree and is represented by the `if` keyword and are written
+like
+
+```xml
+  <py_trees.behaviours.Success name="Feature 1" if="True"/>
+  <py_trees.behaviours.Success name="Feature 2" if="False"/>
+  <py_trees.behaviours.Success name="Feature 3" if="${my_arg1} < 5"/>
+  <py_trees.behaviours.Success name="Feature 4" if="'${my_arg2}' == 'simulation'"/>
+```
+
 ### Logging
 
 By default the parser uses `rclpy.logging` module to log messages. However, if this is not available

package.xml

@@ -2,7 +2,7 @@
 <?xml-model href="http://download.ros.org/schema/package_format3.xsd" schematypens="http://www.w3.org/2001/XMLSchema"?>
 <package format="3">
   <name>py_trees_parser</name>
-  <version>0.6.0</version>
+  <version>0.6.1</version>
   <description>A py_trees xml parser</description>
   <maintainer email="e.l.f.foster@tudelft.nl">Erich L Foster</maintainer>
   <license>Apache-2.0</license>

py_trees_parser/parser.py

@@ -378,6 +378,10 @@ def _create_node(
         name = node_attribs["name"]
         del node_attribs["name"]
 
+        # creating node, so we've handle the condition already
+        if "if" in node_attribs:
+            del node_attribs["if"]
+
         self.logger.debug(f"Found {node_type}")
 
         # name is a special attribute that is handled separately
@@ -453,6 +457,20 @@ def _sub_args(self, args, var):
 
         return None
 
+    def _condition(self, condition):
+        if condition is None:
+            return True
+
+        try:
+            # Safely evaluate the condition
+            self.logger.debug(f"Found conditional: {condition}")
+            result = eval(condition, {"__builtins__": {}}, {})
+            self.logger.debug(f"Condition result: {result}")
+            return bool(result)
+        except Exception as ex:
+            self.logger.error(f"Error evaluating condition '{condition}': {ex}")
+            raise ValueError(f"Error evaluating condition '{condition}'") from ex
+
     def _build_tree(
         self,
         xml_node: Element,
@@ -503,6 +521,9 @@ def _build_tree(
         children = list()
         for child_xml in xml_node:
             self._process_args(child_xml, args)
+            if_cond = child_xml.attrib.get("if")
+            if not self._condition(if_cond):
+                continue
             child = self._build_tree(child_xml, args)
             children.append(child)
 

setup.py

@@ -20,7 +20,7 @@
 
 setup(
     name=package_name,
-    version="0.6.0",
+    version="0.6.1",
     packages=find_packages(exclude=["test"]),
     data_files=[
         ("share/ament_index/resource_index/packages", [os.path.join("resource", package_name)]),

test/data/test_conditional.xml

@@ -0,0 +1,44 @@
+<py_trees.composites.Selector name="Conditional Test" memory="False">
+  <!-- Basic condition: equal comparison -->
+  <py_trees.behaviours.Success name="Advanced Mode Feature" if="'${mode}' == 'advanced'" />
+
+  <!-- Basic condition: not equal comparison -->
+  <py_trees.behaviours.Running name="Non-Basic Mode Feature" if="'${mode}' != 'basic'" />
+
+  <!-- Numeric comparison -->
+  <py_trees.behaviours.Periodic name="High Level Feature" n="3" if="${level} > 5" />
+
+  <!-- Boolean condition -->
+  <py_trees.behaviours.Success name="Debug Feature" if="${enable_debug}"/>
+  <py_trees.behaviours.Success name="Not Debug Feature" if="not ${enable_debug}"/>
+
+  <!-- Multiple children in a conditional -->
+  <py_trees.composites.Sequence name="Conditional Selector" if="${include_all}" memory="True">
+    <py_trees.behaviours.Success name="Feature 1" />
+    <py_trees.behaviours.Success name="Feature 2" />
+    <py_trees.behaviours.Success name="Feature 3" />
+  </py_trees.composites.Sequence>
+
+  <py_trees.composites.Sequence name="Not Conditional Selector" if="not ${include_all}" memory="True">
+    <py_trees.behaviours.Success name="Feature 4" />
+    <py_trees.behaviours.Success name="Feature 5" />
+    <py_trees.behaviours.Success name="Feature 6" />
+  </py_trees.composites.Sequence>
+
+  <subtree name="Included Subtree" if="${include_all}" include="$(ament_index_python.get_package_share_directory('py_trees_parser') + '/test/data/test_conditional_subtree.xml')" >
+    <arg name="name" value="Included Subtree" />
+    <arg name="feature_1" value="Subtree Feature 1"/>
+    <arg name="feature_2" value="Subtree Feature 2"/>
+    <arg name="feature_3" value="Subtree Feature 3"/>
+  </subtree>
+
+  <subtree name="Not Included Subtree" if="not ${include_all}" include="$(ament_index_python.get_package_share_directory('py_trees_parser') + '/test/data/test_conditional_subtree.xml')" >
+    <arg name="name" value="Included Subtree" />
+    <arg name="feature_1" value="Subtree Feature 4"/>
+    <arg name="feature_2" value="Subtree Feature 5"/>
+    <arg name="feature_3" value="Subtree Feature 6"/>
+  </subtree>
+
+  <!-- Always included node -->
+  <py_trees.behaviours.Success name="Always Included" />
+</py_trees.composites.Selector>

test/data/test_conditional_main.xml

@@ -0,0 +1,6 @@
+<subtree name="test_conditional" include="$(os.path.join(ament_index_python.get_package_share_directory('py_trees_parser'), 'test', 'data', 'test_conditional.xml'))" >
+  <arg name="mode" value="advanced" />
+  <arg name="level" value="10" />
+  <arg name="enable_debug" value="True" />
+  <arg name="include_all" value="True" />
+</subtree>

test/data/test_conditional_subtree.xml

@@ -0,0 +1,7 @@
+  <!-- Multiple children in a conditional -->
+<py_trees.composites.Sequence name="${name}" memory="True">
+  <py_trees.behaviours.Success name="${feature_1}" />
+  <py_trees.behaviours.Success name="${feature_2}" />
+  <py_trees.behaviours.Success name="${feature_3}" />
+</py_trees.composites.Sequence>
+

test/test_parser.py

@@ -47,13 +47,13 @@ def setup_parser(ros_init):
     """Setup the parser and test file processing."""
 
     def _setup(tree_file):
-        xml = os.path.join(SHARE_DIR, tree_file)
+        xml = os.path.join(SHARE_DIR, "test", "data", tree_file)
         parser = BTParser(xml, log_level=rclpy.logging.LoggingSeverity.DEBUG)
         try:
             root = parser.parse()
             py_trees_ros.trees.BehaviourTree(root=root, unicode_tree_debug=True)
         except Exception as ex:
-            assert False, f"parse raised an exception {ex}"
+            assert False, f"parse raised an exception {ex}"  # noqa
 
         return root
 
@@ -63,12 +63,12 @@ def _setup(tree_file):
 @pytest.mark.parametrize(
     "tree_file",
     [
-        "test/data/test1.xml",
-        "test/data/test6.xml",
-        "test/data/test_idioms.xml",
-        "test/data/test_function_parse.xml",
-        "test/data/test_subtree_main.xml",
-        "test/data/test_arg_substitution_main.xml",
+        "test1.xml",
+        "test6.xml",
+        "test_idioms.xml",
+        "test_function_parse.xml",
+        "test_subtree_main.xml",
+        "test_arg_substitution_main.xml",
     ],
 )
 def test_tree_parser(setup_parser, tree_file):
@@ -78,7 +78,7 @@ def test_tree_parser(setup_parser, tree_file):
 
 def test_subtree_and_args(setup_parser):
     """Test that subtree arguments are working as expected."""
-    tree_file = "test/data/test_args.xml"
+    tree_file = "test_args.xml"
     root = setup_parser(tree_file)
 
     assert root.name == "Subtree Selector"
@@ -95,7 +95,7 @@ def test_subtree_and_args(setup_parser):
 
 def test_subtree_cascaded_args(setup_parser):
     """Test that cascaded args through subtrees and nested subtrees is working as expected."""
-    tree_file = "test/data/test_cascade_args.xml"
+    tree_file = "test_cascade_args.xml"
     root = setup_parser(tree_file).children[0]
 
     assert root.name == "Subtree Selector"
@@ -112,7 +112,7 @@ def test_subtree_cascaded_args(setup_parser):
 
 def test_arg_substitution_within_strings(setup_parser):
     """Test that argument substitution within strings works as expected."""
-    tree_file = "test/data/test_arg_substitution_main.xml"
+    tree_file = "test_arg_substitution_main.xml"
     root = setup_parser(tree_file)
 
     assert root.name == "Argument Substitution Test"
@@ -134,10 +134,37 @@ def test_arg_substitution_within_strings(setup_parser):
 
 def test_bool(setup_parser):
     """Test that True, true, False, or false are evaluated as booleans."""
-    tree_file = "test/data/test_bool.xml"
+    tree_file = "test_bool.xml"
     root = setup_parser(tree_file)
 
     assert root.name == "No Memory"
     assert root.memory is False
     assert root.children[0].name == "Memory"
     assert root.children[0].memory
+
+
+def test_conditionals(setup_parser):
+    """Test that conditionals include nodes as expected."""
+    tree_file = "test_conditional_main.xml"
+    root = setup_parser(tree_file)
+
+    assert root.name == "Conditional Test"
+
+    children = root.children
+    assert children[0].name == "Advanced Mode Feature"
+    assert children[1].name == "Non-Basic Mode Feature"
+    assert children[2].name == "High Level Feature"
+    assert children[3].name == "Debug Feature"
+    assert children[4].name == "Conditional Selector"
+    assert children[5].name == "Included Subtree"
+    assert children[6].name == "Always Included"
+
+    grand_children = children[4].children
+    assert grand_children[0].name == "Feature 1"
+    assert grand_children[1].name == "Feature 2"
+    assert grand_children[2].name == "Feature 3"
+
+    grand_children = children[5].children
+    assert grand_children[0].name == "Subtree Feature 1"
+    assert grand_children[1].name == "Subtree Feature 2"
+    assert grand_children[2].name == "Subtree Feature 3"