add ros2 param describe (#367)

* add ros2 param describe

Signed-off-by: Dirk Thomas <dirk-thomas@users.noreply.github.com>

* fix linter

Signed-off-by: Dirk Thomas <dirk-thomas@users.noreply.github.com>

ros2param/ros2param/api/__init__.py

@@ -14,6 +14,7 @@
 
 from rcl_interfaces.msg import ParameterType
 from rcl_interfaces.msg import ParameterValue
+from rcl_interfaces.srv import DescribeParameters
 from rcl_interfaces.srv import GetParameters
 from rcl_interfaces.srv import ListParameters
 from rcl_interfaces.srv import SetParameters
@@ -91,6 +92,33 @@ def get_parameter_value(*, string_value):
     return value
 
 
+def call_describe_parameters(*, node, node_name, parameter_names=None):
+    # create client
+    client = node.create_client(
+        DescribeParameters,
+        '{node_name}/describe_parameters'.format_map(locals()))
+
+    # call as soon as ready
+    ready = client.wait_for_service(timeout_sec=5.0)
+    if not ready:
+        raise RuntimeError('Wait for service timed out')
+
+    request = DescribeParameters.Request()
+    if parameter_names:
+        request.names = parameter_names
+    future = client.call_async(request)
+    rclpy.spin_until_future_complete(node, future)
+
+    # handle response
+    response = future.result()
+    if response is None:
+        e = future.exception()
+        raise RuntimeError(
+            "Exception while calling service of node '{node_name}': {e}"
+            .format_map(locals()))
+    return response
+
+
 def call_get_parameters(*, node, node_name, parameter_names):
     # create client
     client = node.create_client(

ros2param/ros2param/verb/describe.py

@@ -0,0 +1,95 @@
+# Copyright 2019 Open Source Robotics Foundation, Inc.
+#
+# 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 rcl_interfaces.msg import ParameterType
+from ros2cli.node.direct import DirectNode
+from ros2cli.node.strategy import add_arguments
+from ros2cli.node.strategy import NodeStrategy
+from ros2node.api import get_absolute_node_name
+from ros2node.api import get_node_names
+from ros2node.api import NodeNameCompleter
+from ros2param.api import call_describe_parameters
+from ros2param.api import ParameterNameCompleter
+from ros2param.verb import VerbExtension
+
+
+class DescribeVerb(VerbExtension):
+    """Show descriptive information about declared parameters."""
+
+    def add_arguments(self, parser, cli_name):  # noqa: D102
+        add_arguments(parser)
+        arg = parser.add_argument(
+            'node_name', help='Name of the ROS node')
+        arg.completer = NodeNameCompleter(
+            include_hidden_nodes_key='include_hidden_nodes')
+        parser.add_argument(
+            '--include-hidden-nodes', action='store_true',
+            help='Consider hidden nodes as well')
+        arg = parser.add_argument(
+            'parameter_names', nargs='+', help='Names of the parameters')
+        arg.completer = ParameterNameCompleter()
+
+    def main(self, *, args):  # noqa: D102
+        with NodeStrategy(args) as node:
+            node_names = get_node_names(
+                node=node, include_hidden_nodes=args.include_hidden_nodes)
+
+        node_name = get_absolute_node_name(args.node_name)
+        if node_name not in {n.full_name for n in node_names}:
+            return 'Node not found'
+
+        with DirectNode(args) as node:
+            response = call_describe_parameters(
+                node=node, node_name=args.node_name,
+                parameter_names=args.parameter_names or None)
+
+            # output response
+            for descriptor in response.descriptors:
+                self._print_descriptor(descriptor)
+
+    def _print_descriptor(self, descriptor):
+        print('Parameter name:', descriptor.name)
+        print('  Type:', get_parameter_type_string(descriptor.type))
+        if descriptor.description:
+            print('  Description:', descriptor.description)
+        if True:
+            print('  Constraints:')
+            if descriptor.read_only:
+                print('    Read only: true')
+            ranges = descriptor.floating_point_range + descriptor.integer_range
+            if ranges:
+                range_ = ranges[0]
+                print('    Min value:', range_.from_value)
+                print('    Max value:', range_.to_value)
+                if range_.step:
+                    print('    Step:', range_.step)
+            if descriptor.additional_constraints:
+                print('    Additional constraints:',
+                      descriptor.additional_constraints)
+
+
+def get_parameter_type_string(parameter_type):
+    mapping = {
+        ParameterType.PARAMETER_BOOL: 'boolean',
+        ParameterType.PARAMETER_INTEGER: 'integer',
+        ParameterType.PARAMETER_DOUBLE: 'double',
+        ParameterType.PARAMETER_STRING: 'string',
+        ParameterType.PARAMETER_BYTE_ARRAY: 'byte array',
+        ParameterType.PARAMETER_BOOL_ARRAY: 'boolean array',
+        ParameterType.PARAMETER_INTEGER_ARRAY: 'integer array',
+        ParameterType.PARAMETER_DOUBLE_ARRAY: 'double array',
+        ParameterType.PARAMETER_STRING_ARRAY: 'string array',
+        ParameterType.PARAMETER_NOT_SET: 'not set',
+    }
+    return mapping[parameter_type]

ros2param/setup.py

@@ -41,6 +41,7 @@
         ],
         'ros2param.verb': [
             'delete = ros2param.verb.delete:DeleteVerb',
+            'describe = ros2param.verb.describe:DescribeVerb',
             'dump = ros2param.verb.dump:DumpVerb',
             'get = ros2param.verb.get:GetVerb',
             'list = ros2param.verb.list:ListVerb',