From 995d3044a466bc9d862700d7949a6dbf93dae42b Mon Sep 17 00:00:00 2001
From: Artem Pavlenko <artem@mapnik.org>
Date: Mon, 26 Feb 2024 14:01:09 +0000
Subject: [PATCH] GeoJSON - allow empty arrays in "coordinates" element for
 Multi* geometries (ref #4431)

---
 include/mapnik/json/create_geometry.hpp       | 36 +++++++++++++++++++
 .../json/geometry_generator_grammar_impl.hpp  |  6 ++--
 test/unit/datasource/geojson.cpp              | 14 +++++---
 3 files changed, 48 insertions(+), 8 deletions(-)

diff --git a/include/mapnik/json/create_geometry.hpp b/include/mapnik/json/create_geometry.hpp
index 9df2d063e..707f5afa6 100644
--- a/include/mapnik/json/create_geometry.hpp
+++ b/include/mapnik/json/create_geometry.hpp
@@ -64,6 +64,10 @@ struct create_linestring
     {
         mapnik::geometry::line_string<double> line;
         std::size_t size = points.size();
+        //if (size < 2)
+        //{
+        //    throw std::runtime_error("RFC 7946: For type \"LineString\", the \"coordinates\" member is an array of two or more positions.");
+        //}
         line.reserve(size);
         for (auto&& pt : points)
         {
@@ -108,6 +112,12 @@ struct create_polygon
         mapnik::geometry::correct(geom_);
     }
 
+    void operator()(ring const& points) const
+    {
+        //POLYGON EMPTY
+        geom_ = std::move(mapnik::geometry::polygon<double>{});
+    }
+
     template<typename T>
     void operator()(T const&) const
     {
@@ -170,6 +180,12 @@ struct create_multilinestring
         geom_ = std::move(multi_line);
     }
 
+    void operator()(ring const& points) const
+    {
+        //MULTILINESTRING EMPTY
+        geom_ = std::move(mapnik::geometry::multi_line_string<double>{});
+    }
+
     template<typename T>
     void operator()(T const&) const
     {
@@ -213,6 +229,26 @@ struct create_multipolygon
         mapnik::geometry::correct(geom_);
     }
 
+    void operator()(rings const& rngs) const
+    {
+        //MULTIPOLYGON
+        mapnik::geometry::multi_polygon<double> multi_poly;
+        mapnik::geometry::polygon<double> poly;
+        std::size_t num_rings = rngs.size();
+        for (std::size_t i = 0; i < num_rings; ++i)
+        {
+            // POLYGON EMPTY
+            multi_poly.emplace_back(mapnik::geometry::polygon<double>{});
+        }
+        geom_ = std::move(multi_poly);
+    }
+
+    void operator()(ring const& points) const
+    {
+        //MULTIPOLYGON EMPTY
+        geom_ = std::move(mapnik::geometry::multi_polygon<double>{});
+    }
+
     template<typename T>
     void operator()(T const&) const
     {
diff --git a/include/mapnik/json/geometry_generator_grammar_impl.hpp b/include/mapnik/json/geometry_generator_grammar_impl.hpp
index 5f003c2f1..2940f6ee9 100644
--- a/include/mapnik/json/geometry_generator_grammar_impl.hpp
+++ b/include/mapnik/json/geometry_generator_grammar_impl.hpp
@@ -83,16 +83,16 @@ geometry_generator_grammar<OutputIterator, Geometry>::geometry_generator_grammar
     linear_ring_coord = lit('[') << -(point_coord % lit(',')) << lit(']')//linestring_coord.alias()
         ;
 
-    polygon_coord = lit('[') << linear_ring_coord % lit(',') << lit(']')
+    polygon_coord = lit('[') << -(linear_ring_coord % lit(',')) << lit(']')
         ;
 
     multi_point_coord = lit('[') << -(point_coord % lit(',')) << lit(']');//linestring_coord.alias()
         ;
 
-    multi_linestring_coord = lit('[') << linestring_coord  % lit(',') << lit(']')
+    multi_linestring_coord = lit('[') << -(linestring_coord  % lit(',')) << lit(']')
         ;
 
-    multi_polygon_coord = lit('[') << polygon_coord  % lit(',') << lit("]")
+    multi_polygon_coord = lit('[') << -(polygon_coord  % lit(',')) << lit("]")
         ;
 
     geometries = geometry % lit(',')
diff --git a/test/unit/datasource/geojson.cpp b/test/unit/datasource/geojson.cpp
index 308e51cff..afd8d84c6 100644
--- a/test/unit/datasource/geojson.cpp
+++ b/test/unit/datasource/geojson.cpp
@@ -125,11 +125,15 @@ TEST_CASE("geojson")
         SECTION("GeoJSON empty Geometries handling")
         {
             auto valid_empty_geometries = {"null", // Point can't be empty
-                                           "{ \"type\": \"LineString\", \"coordinates\": [] }",
-                                           "{ \"type\": \"Polygon\", \"coordinates\": [ [ ] ] } ",
-                                           "{ \"type\": \"MultiPoint\", \"coordinates\": [ ] }",
-                                           "{ \"type\": \"MultiLineString\", \"coordinates\": [ [] ] }",
-                                           "{ \"type\": \"MultiPolygon\", \"coordinates\": [[ []] ] }"};
+                                           "{ \"type\": \"LineString\", \"coordinates\":[]}",
+                                           "{ \"type\": \"Polygon\", \"coordinates\":[]} ",
+                                           "{ \"type\": \"Polygon\", \"coordinates\":[[]]} ",
+                                           "{ \"type\": \"MultiPoint\", \"coordinates\":[]}",
+                                           "{ \"type\": \"MultiLineString\", \"coordinates\":[]}",
+                                           "{ \"type\": \"MultiLineString\", \"coordinates\":[[]]}",
+                                           "{ \"type\": \"MultiPolygon\", \"coordinates\":[]}",
+                                           "{ \"type\": \"MultiPolygon\", \"coordinates\":[[]]}",
+                                           "{ \"type\": \"MultiPolygon\", \"coordinates\": [[[]]] }"};
 
             for (auto const& in : valid_empty_geometries)
             {