Add load_param_file()

README.md

@@ -449,3 +449,43 @@ arg2 = gen.add_arg(name, default_value, description, choices)
 gen.add_node('executable_name', 'package_name',
              condition=launch_generator.condition([arg, '< 10 or ', arg2])) # the node is launched only if arg is less than 10 or greater than 20
 ```
+
+### load_param_file()
+
+`load_param_file()` is a function to load a yaml file to parameter dictionary.
+The function can replace the value of parameters written in the form of `$(arg arg_name)` like `subst_value` of ROS1 with `LaunchConfiguration(arg_name)`.
+
+Example of yaml file:
+
+```yaml
+node_name:
+    ros__parameters:
+        param1: $(arg arg_name)
+        param2:
+            sub1: prefix_$(arg arg_name)
+            sub2: $(arg arg_name)_suffix
+            sub3: $(arg arg_name)_$(arg_name2)
+```
+
+```python
+arg = gen.add_arg('arg_name', 'default_value')
+arg2 = gen.add_arg('arg_name2', 'default_value')
+param_dict = launch_generator.load_param_file('package_name', 'config/file_name.yaml')
+
+# param_dict = {
+#     'node_name': {
+#         'ros__parameters': {
+#             'param1': launch.substitutions.LaunchConfiguration('arg_name'),
+#             'param2': {
+#                 'sub1': ['prefix_', launch.substitutions.LaunchConfiguration('arg_name')],
+#                 'sub2': [launch.substitutions.LaunchConfiguration('arg_name'), '_suffix'],
+#                 'sub3': [launch.substitutions.LaunchConfiguration('arg_name'), '_', launch.substitutions.LaunchConfiguration('arg_name2')],
+#             }
+#         }
+#     }
+# }
+
+gen.add_node('executable_name', 'package_name', parameters=[param_dict['node_name']['ros__parameters']])
+
+return LaunchDescription(gen.generate_launch_description())
+```

pyproject.toml

@@ -5,7 +5,7 @@ description = "Simple launch file generator for ROS2."
 authors = [
     { name = "Tatsuro Sakaguchi", email = "tatsuro.sakaguchi@g.softbank.co.jp" },
 ]
-dependencies = ["launch", "launch_ros"]
+dependencies = ["launch", "launch_ros", "pyyaml"]
 readme = "README.md"
 requires-python = ">= 3.10"
 

setup.py

@@ -25,4 +25,5 @@
     url='https://github.com/Tacha-S/launch_generator',
     package_dir={'': 'src'},
     packages=setuptools.find_packages('src', include=['launch_generator']),
+    install_requires=['pyyaml'],
 )

src/launch_generator/__init__.py

@@ -17,11 +17,13 @@
 from launch_generator.event_handler_generator import EventTriggerType
 from launch_generator.generator import Generator
 from launch_generator.utils import condition
+from launch_generator.utils import load_param_file
 from launch_generator.utils import package_path
 
 __all__ = [
     'EventTriggerType',
     'Generator',
     'condition',
+    'load_param_file',
     'package_path',
 ]

src/launch_generator/utils.py

@@ -15,10 +15,12 @@
 #
 
 import pathlib
+import re
 import typing
 
 import launch
 import launch_ros
+import yaml
 
 
 def condition(
@@ -71,3 +73,66 @@ def package_path(package_name: str) -> pathlib.Path:
         Package path.
     """
     return pathlib.Path(launch_ros.substitutions.FindPackageShare(package_name).find(package_name))
+
+
+def load_param_file(package: launch.some_substitutions_type.SomeSubstitutionsType,
+                    relative_file_path: typing.Text) -> dict:
+    """Load param file to dict. Replace $(arg xxx) with LaunchConfiguration(xxx).
+
+    Args:
+        package: Package name.
+        relative_file_path: Relative file path.
+
+    Returns:
+        Parameters.
+    """
+    path = package_path(package) / relative_file_path
+    with open(path, 'r') as f:
+        parameters = yaml.safe_load(f.read())
+
+    def __replace_arg(params: dict[str, typing.Any]) -> None:
+        """Replace $(arg xxx) with LaunchConfiguration(xxx).
+
+        Args:
+            params: Parameters.
+        """
+        regex = re.compile(r'\$\(arg \w+?\)')
+        replaced_keys = {}
+        for key, value in params.items():
+            if isinstance(value, dict):
+                __replace_arg(value)
+            elif isinstance(value, str):
+                match = regex.findall(value)
+                if match:
+                    replaced = []
+                    start = 0
+                    for m in match:
+                        i = value.find(m)
+                        if i > start:
+                            replaced.append(value[start:i])
+                        replaced.append(launch.substitutions.LaunchConfiguration(m[6:-1]))
+                        start = i + len(m)
+                    if start < len(value):
+                        replaced.append(value[start:])
+                    params[key] = replaced
+                    value = replaced
+
+            match = regex.findall(key)
+            if match:
+                replaced = []
+                start = 0
+                for m in match:
+                    i = key.find(m)
+                    if i > start:
+                        replaced.append(key[start:i])
+                    replaced.append(launch.substitutions.LaunchConfiguration(m[6:-1]))
+                    start = i + len(m)
+                if start < len(key):
+                    replaced.append(key[start:])
+                replaced = tuple(replaced)
+                replaced_keys[replaced] = value
+        params.update(replaced_keys)
+
+    __replace_arg(parameters)
+
+    return parameters