Add memory_datasource test + fix returning of invalid_featureset for emptyset

src/memory_datasource.cpp

@@ -117,12 +117,20 @@ datasource::datasource_t memory_datasource::type() const
 
 featureset_ptr memory_datasource::features(const query& q) const
 {
+    if (features_.empty())
+    {
+        return mapnik::make_invalid_featureset();
+    }
     return std::make_shared<memory_featureset>(q.get_bbox(),*this,bbox_check_);
 }
 
 
 featureset_ptr memory_datasource::features_at_point(coord2d const& pt, double tol) const
 {
+    if (features_.empty())
+    {
+        return mapnik::make_invalid_featureset();
+    }
     box2d<double> box = box2d<double>(pt.x, pt.y, pt.x, pt.y);
     box.pad(tol);
     MAPNIK_LOG_DEBUG(memory_datasource) << "memory_datasource: Box=" << box << ", Point x=" << pt.x << ",y=" << pt.y;

test/unit/datasource/memory.cpp

@@ -0,0 +1,46 @@
+/*****************************************************************************
+ *
+ * This file is part of Mapnik (c++ mapping toolkit)
+ *
+ * Copyright (C) 2015 Artem Pavlenko
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
+ *
+ *****************************************************************************/
+
+#include "catch.hpp"
+#include "ds_test_util.hpp"
+
+#include <mapnik/unicode.hpp>
+#include <mapnik/datasource.hpp>
+#include <mapnik/memory_datasource.hpp>
+#include <mapnik/datasource_cache.hpp>
+
+
+TEST_CASE("memory datasource") {
+
+    SECTION("empty featureset")
+    {
+        mapnik::parameters params;
+        mapnik::datasource_ptr ds = std::make_shared<mapnik::memory_datasource>(params);
+        CHECK(ds != nullptr);
+        auto fs = all_features(ds);
+        REQUIRE(!mapnik::is_valid(fs));
+        while (auto f = fs->next())
+        {
+            CHECK(false); // shouldn't get here
+        }
+    }
+}