Add method in Node to resolve a topic or service name

rclpy/rclpy/node.py

@@ -1091,6 +1091,32 @@ def remove_waitable(self, waitable: Waitable) -> None:
         self.__waitables.remove(waitable)
         self._wake_executor()
 
+    def resolve_topic_name(self, topic: str, *, only_expand: bool = False) -> str:
+        """
+        Return a topic name expanded and remapped.
+
+        :param topic: topic name to be expanded and remapped.
+        :param only_expand: if `True`, remapping rules won't be applied.
+        :return: a fully qualified topic name,
+            result of applying expansion and remapping to the given `topic`.
+        """
+        with self.handle as capsule:
+            return _rclpy.rclpy_resolve_name(capsule, topic, only_expand, False)
+
+    def resolve_service_name(
+        self, service: str, *, only_expand: bool = False
+    ) -> str:
+        """
+        Return a service name expanded and remapped.
+
+        :param service: service name to be expanded and remapped.
+        :param only_expand: if `True`, remapping rules won't be applied.
+        :return: a fully qualified service name,
+            result of applying expansion and remapping to the given `service`.
+        """
+        with self.handle as capsule:
+            return _rclpy.rclpy_resolve_name(capsule, service, only_expand, True)
+
     def create_publisher(
         self,
         msg_type,

rclpy/src/rclpy/_rclpy.c

@@ -1693,6 +1693,61 @@ rclpy_remap_topic_name(PyObject * Py_UNUSED(self), PyObject * args)
   return result;
 }
 
+
+/// Expand and remap a topic name
+/**
+ * Raises ValueError if the capsule is not the correct type
+ *
+ * \param[in] pynode Capsule pointing to the node
+ * \param[in] topic_name topic string to be remapped
+ * \param[in] only_expand when `false`, remapping rules are ignored
+ * \param[in] is_service `true` for service names, `false` for topic names
+ * \return expanded and remapped topic name
+ */
+static PyObject *
+rclpy_resolve_name(PyObject * Py_UNUSED(self), PyObject * args)
+{
+  PyObject * pynode = NULL;
+  const char * name = NULL;
+  int only_expand = false;
+  int is_service = false;
+
+
+  if (!PyArg_ParseTuple(args, "Ospp", &pynode, &name, &only_expand, &is_service)) {
+    return NULL;
+  }
+
+  const rcl_node_t * node = rclpy_handle_get_pointer_from_capsule(pynode, "rcl_node_t");
+  if (node == NULL) {
+    return NULL;
+  }
+  const rcl_node_options_t * node_options = rcl_node_get_options(node);
+  if (node_options == NULL) {
+    return NULL;
+  }
+
+  char * output_cstr = NULL;
+  rcl_ret_t ret = rcl_node_resolve_name(
+    node,
+    name,
+    node_options->allocator,
+    is_service,
+    only_expand,
+    &output_cstr);
+  if (ret != RCL_RET_OK) {
+    PyErr_Format(
+      PyExc_RuntimeError, "Failed to resolve name %s: %s", name, rcl_get_error_string().str);
+    rcl_reset_error();
+    return NULL;
+  }
+
+  PyObject * result = PyUnicode_FromString(output_cstr);
+  node_options->allocator.deallocate(output_cstr, node_options->allocator.state);
+
+  return result;
+}
+
+
 /// Handle destructor for publisher
 static void
 _rclpy_destroy_publisher(void * p)
@@ -5697,6 +5752,10 @@ static PyMethodDef rclpy_methods[] = {
     rclpy_get_validation_error_for_node_name, METH_VARARGS,
     "Get the error message and invalid index of a node name or None if valid."
   },
+  {
+    "rclpy_resolve_name", rclpy_resolve_name, METH_VARARGS,
+    "Expand and remap a topic or service name."
+  },
   {
     "rclpy_create_publisher", rclpy_create_publisher, METH_VARARGS,
     "Create a Publisher."

rclpy/test/test_node.py

@@ -1920,5 +1920,21 @@ def test_node_get_fully_qualified_name(self):
         rclpy.shutdown(context=g_context)
 
 
+def test_node_resolve_name():
+    context = rclpy.Context()
+    rclpy.init(
+        args=['--ros-args', '-r', 'foo:=bar'],
+        context=context,
+    )
+    node = rclpy.create_node('test_rclpy_node_resolve_name', namespace='/my_ns', context=context)
+    assert node.resolve_topic_name('foo') == '/my_ns/bar'
+    assert node.resolve_topic_name('/abs') == '/abs'
+    assert node.resolve_topic_name('foo', only_expand=True) == '/my_ns/foo'
+    assert node.resolve_service_name('foo') == '/my_ns/bar'
+    assert node.resolve_service_name('/abs') == '/abs'
+    assert node.resolve_service_name('foo', only_expand=True) == '/my_ns/foo'
+    rclpy.shutdown(context=context)
+
+
 if __name__ == '__main__':
     unittest.main()