GeJSON - allow empty FeatureCollections (#4035)

plugins/input/geojson/geojson_datasource.cpp

@@ -274,7 +274,7 @@ void geojson_datasource::initialise_index(Iterator start, Iterator end)
     try
     {
         mapnik::json::extract_bounding_boxes(itr, end, boxes);
-        if (itr != end || boxes.empty()) throw std::exception();
+        if (itr != end) throw std::exception();
         // bulk insert initialise r-tree
         tree_ = std::make_unique<spatial_index_type>(boxes);
         // calculate total extent
@@ -366,7 +366,7 @@ void geojson_datasource::parse_geojson(Iterator start, Iterator end)
     {
         boxes_type boxes;
         mapnik::json::extract_bounding_boxes(itr, end, boxes);
-        if (itr != end || boxes.empty()) throw std::exception(); //ensure we've consumed all input and we extracted at least one bbox;
+        if (itr != end) throw std::exception(); //ensure we've consumed all input
         for (auto const& item : boxes)
         {
             auto const& geometry_index = std::get<1>(item);

test/unit/datasource/geojson.cpp

@@ -108,7 +108,7 @@ TEST_CASE("geojson") {
                 params["type"] = "geojson";
                 params["file"] = "./test/data/json/empty_featurecollection.json";
                 params["cache_features"] = cache_features;
-                REQUIRE_THROWS(mapnik::datasource_cache::instance().create(params));
+                REQUIRE(mapnik::datasource_cache::instance().create(params));
             }
         }