Add has_node_params launch utility

nav2_common/nav2_common/launch/__init__.py

@@ -12,5 +12,6 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
+from .has_node_params import HasNodeParams
 from .rewritten_yaml import RewrittenYaml
 from .replace_string import ReplaceString

nav2_common/nav2_common/launch/has_node_params.py

@@ -0,0 +1,61 @@
+# Copyright (c) 2021 PAL Robotics S.L.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+from typing import List
+from typing import Text
+
+import yaml
+import launch
+
+
+class HasNodeParams(launch.Substitution):
+    """
+    Substitution that checks if a param file contains parameters for a node.
+
+    Used in launch system
+    """
+
+    def __init__(self,
+                 source_file: launch.SomeSubstitutionsType,
+                 node_name: Text) -> None:
+        super().__init__()
+        """
+    Construct the substitution
+
+    :param: source_file the parameter YAML file
+    :param: node_name the name of the node to check
+    """
+
+        # import here to avoid loop
+        from launch.utilities import normalize_to_list_of_substitutions
+        self.__source_file = normalize_to_list_of_substitutions(source_file)
+        self.__node_name = node_name
+
+    @property
+    def name(self) -> List[launch.Substitution]:
+        """Getter for name."""
+        return self.__source_file
+
+    def describe(self) -> Text:
+        """Return a description of this substitution as a string."""
+        return ''
+
+    def perform(self, context: launch.LaunchContext) -> Text:
+        yaml_filename = launch.utilities.perform_substitutions(
+            context, self.name)
+        data = yaml.safe_load(open(yaml_filename, 'r'))
+
+        if self.__node_name in data.keys():
+            return "True"
+        return "False"