Support passing parameters as a dictionary (#138)

* Pass shallow dicts of parameters

* Support nested dicts

* Support passing parameter lists

* Support non-substitution types in param lists

* Error on nested lists

* Tests for invalid dicts

* Invalid param dicts show on execution of nodes

Factor out test utility code

* Add test checking resulting parameters file

* Test more complex dictionary

* Depend on pyyaml

* Don't allow random types to be passed in dict

* Docs

* Error if node name isn't specified by params dict is given

* set() -> {}

* Linter fix

* Add todo for deleting generated files

* Linter fix

launch_ros/launch_ros/actions/node.py

@@ -17,13 +17,15 @@
 import logging
 import os
 import pathlib
+from tempfile import NamedTemporaryFile
 from typing import Dict  # noqa: F401
 from typing import Iterable
 from typing import List
 from typing import Optional
 from typing import Text  # noqa: F401
 from typing import Tuple
 
+from launch import Substitution
 from launch.action import Action
 from launch.actions import ExecuteProcess
 from launch.launch_context import LaunchContext
@@ -39,6 +41,8 @@
 from rclpy.validate_namespace import validate_namespace
 from rclpy.validate_node_name import validate_node_name
 
+import yaml
+
 _logger = logging.getLogger(name='launch_ros')
 
 
@@ -87,11 +91,28 @@ def __init__(
         If no node_namespace is given, then the default namespace `/` is
         assumed.
 
+        The parameters are passed as a list, with each element either a yaml
+        file that contains parameter rules (string or pathlib.Path to the full
+        path of the file), or a dictionary that specifies parameter rules.
+        Keys of the dictionary can be strings or an iterable of Substitutions
+        that will be expanded to a string.
+        Values in the dictionary can be strings, integers, floats, or tuples
+        of Substitutions that will be expanded to a string.
+        Additionally, values in the dictionary can be lists of the
+        aforementioned types, or another dictionary with the same properties.
+        A yaml file with the resulting parameters from the dictionary will be
+        written to a temporary file, the path to which will be passed to the
+        node.
+        Multiple dictionaries/files can be passed: each file path will be
+        passed in in order to the node (where the last definition of a
+        parameter takes effect).
+
         :param: package the package in which the node executable can be found
         :param: node_executable the name of the executable to find
         :param: node_name the name of the node
         :param: node_namespace the ros namespace for this Node
-        :param: parameters list of names of yaml files with parameter rules
+        :param: parameters list of names of yaml files with parameter rules,
+            or dictionaries of parameters.
         :param: remappings ordered list of 'to' and 'from' string pairs to be
             passed to the node as ROS remapping rules
         :param: arguments list of extra arguments for the node
@@ -111,13 +132,16 @@ def __init__(
             ros_args_index += 1
         if parameters is not None:
             ensure_argument_type(parameters, (list), 'parameters', 'Node')
-            # All arguments are paths to files with parameters (or substitutions that evaluate
-            # to paths).
-            # TODO(dhood): add support for parameter dicts.
-            parameter_types = list(SomeSubstitutionsType_types_tuple) + [pathlib.Path]
+            # All elements in the list are paths to files with parameters (or substitutions that
+            # evaluate to paths), or dictionaries of parameters (fields can be substitutions).
+            parameter_types = list(SomeSubstitutionsType_types_tuple) + [pathlib.Path, dict]
             i = 0
             for param in parameters:
                 ensure_argument_type(param, parameter_types, 'parameters[{}]'.format(i), 'Node')
+                if isinstance(param, dict) and node_name is None:
+                    raise RuntimeError(
+                        'If a dictionary of parameters is specified, the node name must also be '
+                        'specified. See https://github.com/ros2/launch/issues/139')
                 i += 1
                 cmd += [LocalSubstitution(
                     'ros_specific_arguments[{}]'.format(ros_args_index),
@@ -146,7 +170,7 @@ def __init__(
         self.__expanded_node_name = '<node_name_unspecified>'
         self.__expanded_node_namespace = '/'
         self.__final_node_name = None  # type: Optional[Text]
-        self.__expanded_parameters = None  # type: Optional[List[Text]]
+        self.__expanded_parameter_files = None  # type: Optional[List[Text]]
         self.__expanded_remappings = None  # type: Optional[List[Tuple[Text, Text]]]
 
         self.__substitutions_performed = False
@@ -158,6 +182,70 @@ def node_name(self):
             raise RuntimeError("cannot access 'node_name' before executing action")
         return self.__final_node_name
 
+    def _create_params_file_from_dict(self, context, params):
+        with NamedTemporaryFile(mode='w', prefix='launch_params_', delete=False) as h:
+            param_file_path = h.name
+            # TODO(dhood): clean up generated parameter files.
+
+            def perform_substitution_if_applicable(context, var):
+                if isinstance(var, (int, float, str)):
+                    # No substitution necessary.
+                    return var
+                if isinstance(var, Substitution):
+                    return perform_substitutions(context, normalize_to_list_of_substitutions(var))
+                if isinstance(var, tuple):
+                    try:
+                        return perform_substitutions(
+                            context, normalize_to_list_of_substitutions(var))
+                    except TypeError:
+                        raise TypeError(
+                            'Invalid element received in parameters dictionary '
+                            '(not all tuple elements are Substitutions): {}'.format(var))
+                else:
+                    raise TypeError(
+                        'Unsupported type received in parameters dictionary: {}'
+                        .format(type(var)))
+
+            def expand_dict(input_dict):
+                expanded_dict = {}
+                for k, v in input_dict.items():
+                    # Key (parameter/group name) can only be a string/Substitutions that evaluates
+                    # to a string.
+                    expanded_key = perform_substitutions(
+                        context, normalize_to_list_of_substitutions(k))
+                    if isinstance(v, dict):
+                        # Expand the nested dict.
+                        expanded_value = expand_dict(v)
+                    elif isinstance(v, list):
+                        # Expand each element.
+                        expanded_value = []
+                        for e in v:
+                            if isinstance(e, list):
+                                raise TypeError(
+                                    'Nested lists are not supported for parameters: {} found in {}'
+                                    .format(e, v))
+                            expanded_value.append(perform_substitution_if_applicable(context, e))
+                    # Tuples are treated as Substitution(s) to be concatenated.
+                    elif isinstance(v, tuple):
+                        for e in v:
+                            ensure_argument_type(
+                                e, SomeSubstitutionsType_types_tuple,
+                                'parameter dictionary tuple entry', 'Node')
+                        expanded_value = perform_substitutions(
+                            context, normalize_to_list_of_substitutions(v))
+                    else:
+                        expanded_value = perform_substitution_if_applicable(context, v)
+                    expanded_dict[expanded_key] = expanded_value
+                return expanded_dict
+
+            expanded_dict = expand_dict(params)
+            param_dict = {
+                self.__expanded_node_name: {'ros__parameters': expanded_dict}}
+            if self.__expanded_node_namespace:
+                param_dict = {self.__expanded_node_namespace: param_dict}
+            yaml.dump(param_dict, h, default_flow_style=False)
+            return param_file_path
+
     def _perform_substitutions(self, context: LaunchContext) -> None:
         try:
             if self.__substitutions_performed:
@@ -192,18 +280,22 @@ def _perform_substitutions(self, context: LaunchContext) -> None:
         self.__final_node_name += '/' + self.__expanded_node_name
         # expand parameters too
         if self.__parameters is not None:
-            self.__expanded_parameters = []
-            for param_file_path in self.__parameters:
-                if isinstance(param_file_path, pathlib.Path):
-                    param_file_path = str(param_file_path)
-                expanded_param_file_path = perform_substitutions(
-                    context, normalize_to_list_of_substitutions(param_file_path))
-                if not os.path.isfile(expanded_param_file_path):
+            self.__expanded_parameter_files = []
+            for params in self.__parameters:
+                if isinstance(params, dict):
+                    param_file_path = self._create_params_file_from_dict(context, params)
+                else:
+                    if isinstance(params, pathlib.Path):
+                        param_file_path = str(params)
+                    else:
+                        param_file_path = perform_substitutions(
+                            context, normalize_to_list_of_substitutions(params))
+                if not os.path.isfile(param_file_path):
                     _logger.warn(
-                        'Parameter file path is not a file: {}'.format(expanded_param_file_path))
+                        'Parameter file path is not a file: {}'.format(param_file_path))
                     # Don't skip adding the file to the parameter list since space has been
                     # reserved for it in the ros_specific_arguments.
-                self.__expanded_parameters.append(expanded_param_file_path)
+                self.__expanded_parameter_files.append(param_file_path)
         # expand remappings too
         if self.__remappings is not None:
             self.__expanded_remappings = []
@@ -226,8 +318,8 @@ def execute(self, context: LaunchContext) -> Optional[List[Action]]:
             ros_specific_arguments.append('__node:={}'.format(self.__expanded_node_name))
         if self.__node_namespace is not None:
             ros_specific_arguments.append('__ns:={}'.format(self.__expanded_node_namespace))
-        if self.__expanded_parameters is not None:
-            for param_file_path in self.__expanded_parameters:
+        if self.__expanded_parameter_files is not None:
+            for param_file_path in self.__expanded_parameter_files:
                 ros_specific_arguments.append('__params:={}'.format(param_file_path))
         if self.__expanded_remappings is not None:
             for remapping_from, remapping_to in self.__expanded_remappings:

launch_ros/package.xml

@@ -14,6 +14,7 @@
   <depend>lifecycle_msgs</depend>
   <depend>osrf_pycommon</depend>
   <depend>rclpy</depend>
+  <depend>python3-yaml</depend>
 
   <test_depend>ament_copyright</test_depend>
   <test_depend>ament_flake8</test_depend>

launch_ros/setup.py

@@ -10,6 +10,7 @@
         'ament_index_python',
         'launch',
         'osrf_pycommon',
+        'pyyaml',
     ],
     zip_safe=True,
     author='William Woodall',

test_launch_ros/package.xml

@@ -15,6 +15,7 @@
   <test_depend>demo_nodes_py</test_depend>
   <test_depend>launch_ros</test_depend>
   <test_depend>python3-pytest</test_depend>
+  <test_depend>python3-yaml</test_depend>
 
   <export>
     <build_type>ament_python</build_type>

test_launch_ros/setup.py

@@ -9,6 +9,7 @@
         'setuptools',
         'demo_nodes_py',
         'launch_ros',
+        'pyyaml',
     ],
     zip_safe=True,
     author='William Woodall',

test_launch_ros/test/test_launch_ros/actions/example_parameters.yaml

@@ -1,8 +1,9 @@
-talker:
-    ros__parameters:
-        some_int: 42
-        a_string: "Hello world"
-        some_list:
-            sub_list:
-                some_integers: [1, 2, 3, 4]
-                some_doubles : [3.14, 2.718]
+/my_ns:
+    my_node:
+        ros__parameters:
+            some_int: 42
+            a_string: "Hello world"
+            some_list:
+                sub_list:
+                    some_integers: [1, 2, 3, 4]
+                    some_doubles : [3.14, 2.718]