Expose AnyParameter map to C++ API and extend in SWIG

src/interfaces/python/swig_typemaps.i

@@ -1417,7 +1417,7 @@ def _internal_get_param(self, name):
         except Exception:
             raise
     if name in self.parameter_names():
-        raise ValueError("The current Python API does not have a getter for '{}'".format(name))
+        raise ValueError("The current Python API does not have a getter for '{}' of type '{}'".format(name, self.parameter_type(name)))
     else:
         raise KeyError("There is no parameter called '{}' in {}".format(name, self.get_name()))
 

src/interfaces/swig/SGBase.i

@@ -1,3 +1,9 @@
+/*
+ * This software is distributed under BSD 3-clause license (see LICENSE file).
+ *
+ * Authors: Gil Hoben, Heiko Strathmann, Sergey Lisitsyn
+ */
+
 /* base includes required by any module */
 %include "stdint.i"
 %include "std_string.i"
@@ -373,12 +379,39 @@ namespace std {
 %include <shogun/base/Parallel.h>
 %include <shogun/lib/StoppableSGObject.h>
 
-#ifdef SWIGPYTHON
 namespace shogun
 {
-
     %extend CSGObject
     {
+        std::vector<std::string> parameter_names() const {
+            std::vector<std::string> result;
+            for (auto const& each: $self->get_params()) {
+                result.push_back(each.first);
+            }
+            return result;
+        }
+
+        std::string parameter_type(const std::string& name) const {
+            auto params = $self->get_params();
+            if (params.find(name) != params.end()) {
+                return params[name].get()->get_value().type();
+            }
+            else {
+                SG_SERROR("There is no parameter called '%s' in %s", name.c_str(), $self->get_name());
+            }
+        }
+
+        std::string parameter_description(const std::string& name) const {
+            auto params = $self->get_params();
+            if (params.find(name) != params.end()) {
+                return params[name].get()->get_properties().get_description();
+            }
+            else {
+                SG_SERROR("There is no parameter called '%s' in %s", name.c_str(), $self->get_name());
+            }
+        }
+
+#ifdef SWIGPYTHON
         std::string __str__() const
         {
             return $self->to_string();
@@ -485,9 +518,11 @@ namespace shogun
         }
 
         /*int getbuffer(PyObject *obj, Py_buffer *view, int flags) { return 0; }*/
+#endif //SWIGPYTHON
     }
 }
 
+#ifdef SWIGPYTHON
 %pythoncode %{
 try:
     import copy_reg

src/shogun/base/SGObject.cpp

@@ -975,14 +975,16 @@ std::string CSGObject::to_string() const
 	return ss.str();
 }
 
-std::vector<std::string> CSGObject::parameter_names() const
+#ifndef SWIG // SWIG should skip this part
+std::map<std::string, std::shared_ptr<const AnyParameter>> CSGObject::get_params() const
 {
-	std::vector<std::string> result;
-	std::transform(self->map.cbegin(), self->map.cend(), std::back_inserter(result),
-		// FIXME: const auto& each fails on gcc 4.8.4
-		[](const std::pair<BaseTag, AnyParameter>& each) -> std::string { return each.first.name(); });
+	std::map<std::string, std::shared_ptr<const AnyParameter>> result;
+	for (auto const& each: self->map) {
+		result.emplace(each.first.name(), std::make_shared<const AnyParameter>(each.second));
+	}
 	return result;
 }
+#endif
 
 bool CSGObject::equals(const CSGObject* other) const
 {
@@ -1068,11 +1070,19 @@ CSGObject* CSGObject::get(const std::string& name)
 	if (auto* result = get_sgobject_type_dispatcher<CLabels>(name))
 		return result;
 
-
-	SG_ERROR(
-	    "Cannot get parameter %s::%s of type %s as object, not object type.\n",
-	    get_name(), name.c_str(),
-	    self->map[BaseTag(name)].get_value().type().c_str());
+	if (self->map.find(BaseTag(name)) != self->map.end())
+	{
+		SG_ERROR(
+		    "Cannot get parameter %s::%s of type %s as object, not a shogun "
+		    "object base type.\n",
+		    get_name(), name.c_str(),
+		    self->map[BaseTag(name)].get_value().type().c_str());
+	}
+	else
+	{
+		SG_ERROR(
+		    "There is no parameter '%s' in %s.\n", name.c_str(), get_name());
+	}
 	return nullptr;
 }
 

src/shogun/base/SGObject.h

@@ -28,6 +28,7 @@
 
 #include <utility>
 #include <vector>
+#include <map>
 
 /** \namespace shogun
  * @brief all of classes and functions are contained in the shogun namespace
@@ -79,14 +80,13 @@ template <class T> class SGStringList;
 #define VARARG_IMPL(base, count, ...) VARARG_IMPL2(base, count, __VA_ARGS__)
 #define VARARG(base, ...) VARARG_IMPL(base, VA_NARGS(__VA_ARGS__), __VA_ARGS__)
 
-#define SG_ADD3(param, name, description)    \
+#define SG_ADD3(param, name, description)                                      \
 	{                                                                          \
 		this->m_parameters->add(param, name, description);                     \
-		this->watch_param(                                                     \
-		    name, param, AnyParameterProperties()); 						   \
+		this->watch_param(name, param, AnyParameterProperties(description));   \
 	}
 
-#define SG_ADD4(param, name, description, param_properties)                     \
+#define SG_ADD4(param, name, description, param_properties)                    \
 	{                                                                          \
 		AnyParameterProperties pprop =                                         \
 		    AnyParameterProperties(description, param_properties);             \
@@ -533,11 +533,13 @@ class CSGObject
 	 */
 	virtual std::string to_string() const;
 
-	/** Returns set of all parameter names of the object.
+	/** Returns map of parameter names and AnyParameter pairs
+	 * of the object.
 	 *
 	 */
-	std::vector<std::string> parameter_names() const;
-
+#ifndef SWIG // SWIG should skip this part
+	std::map<std::string, std::shared_ptr<const AnyParameter>> get_params() const;
+#endif
 	/** Specializes a provided object to the specified type.
 	 * Throws exception if the object cannot be specialized.
 	 *

tests/unit/base/SGObjectAll_unittest.cc

@@ -293,7 +293,12 @@ TEST(SGObjectAll, DISABLED_tag_coverage)
 		std::vector<std::string> old_names;
 		for (auto i : range(obj->m_parameters->get_num_parameters()))
 			old_names.push_back(obj->m_parameters->get_parameter(i)->m_name);
-		auto tag_names = obj->parameter_names();
+
+		std::vector<std::string> tag_names;
+		std::transform(obj->get_params().cbegin(), obj->get_params().cend(), std::back_inserter(tag_names),
+			[](const std::pair<std::string, std::shared_ptr<const AnyParameter>>& each) -> std::string {
+			return each.first;
+		});
 
 		// hack to increase readability of error messages
 		old_names.push_back("_Shogun class: " + class_name);