From b4b5e33b05456947ea32aab583c5758fba166337 Mon Sep 17 00:00:00 2001
From: artemp <artem@mapnik.org>
Date: Tue, 21 Mar 2017 12:43:42 +0000
Subject: [PATCH] refactor WKT generator to retain geometry type for `empty`
 geometries (avoid short-cutting to `POINT EMPTY`)

For example:

| in |   | out   |
|`POINT EMPTY` |  <--> | 'POINT EMPTY`|
|`LINESTRING EMPTY` |  --> | 'POINT EMPTY`|

| in |   | out   |
|`POINT EMPTY` |  <--> | 'POINT EMPTY`|
|`LINESTRING EMPTY` |  <--> | 'LINESTRING EMPTY`|
etc.
---
 .../mapnik/wkt/wkt_generator_grammar_impl.hpp | 39 +++++++++++++------
 1 file changed, 27 insertions(+), 12 deletions(-)

diff --git a/include/mapnik/wkt/wkt_generator_grammar_impl.hpp b/include/mapnik/wkt/wkt_generator_grammar_impl.hpp
index d627aa95c..4daa2547a 100644
--- a/include/mapnik/wkt/wkt_generator_grammar_impl.hpp
+++ b/include/mapnik/wkt/wkt_generator_grammar_impl.hpp
@@ -49,36 +49,51 @@ wkt_generator_grammar<OutputIterator, Geometry>::wkt_generator_grammar()
         lit("POINT EMPTY") // special case for geometry_empty
         ;
 
-    point = lit("POINT(") << coordinate << lit(' ') << coordinate << lit(")")
+    point = lit("POINT(") << point_coord << lit(")")
         ;
-    linestring = lit("LINESTRING(") << linestring_coord << lit(")")
+
+    linestring = lit("LINESTRING") << (linestring_coord | lit(" EMPTY"))
         ;
-    polygon = lit("POLYGON(") << polygon_coord << lit(")")
+
+    polygon = lit("POLYGON") << (polygon_coord | lit(" EMPTY"))
         ;
-    multi_point = lit("MULTIPOINT(") << multi_point_coord << lit(")")
+
+    multi_point = lit("MULTIPOINT") << (multi_point_coord | lit(" EMPTY"))
         ;
-    multi_linestring = lit("MULTILINESTRING(") << multi_linestring_coord << lit(")")
+
+    multi_linestring = lit("MULTILINESTRING") << (multi_linestring_coord | lit(" EMPTY"))
         ;
-    multi_polygon = lit("MULTIPOLYGON(") << multi_polygon_coord << lit(")")
+
+    multi_polygon = lit("MULTIPOLYGON") << (multi_polygon_coord | lit(" EMPTY"))
         ;
-    geometry_collection = lit("GEOMETRYCOLLECTION(") << geometries  << lit(")")
+
+    geometry_collection = lit("GEOMETRYCOLLECTION") << (lit("(") << geometries  << lit(")") | lit(" EMPTY"))
         ;
+
     point_coord = coordinate << lit(' ') << coordinate
         ;
-    linestring_coord = point_coord % lit(',')
+
+    linestring_coord = lit("(") << point_coord % lit(',') << lit(")")
         ;
-    polygon_coord = lit('(') << exterior_ring_coord << lit(')') << interior_ring_coord
+
+    polygon_coord = lit("(") << exterior_ring_coord << interior_ring_coord << lit(")")
         ;
+
     exterior_ring_coord = linestring_coord.alias()
         ;
-    interior_ring_coord =  *(lit(",(") << exterior_ring_coord << lit(')'))
+
+    interior_ring_coord =  *(lit(",") << exterior_ring_coord)
         ;
+
     multi_point_coord = 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(',')
         ;