Merge pull request #3971 from lightmare/fix-topojson-empty

Accept TopoJSON with no objects

include/mapnik/json/topojson_grammar_x3_def.hpp

@@ -276,7 +276,7 @@ using x3::lit;
 using x3::double_;
 using x3::int_;
 using x3::omit;
-using x3::char_;
+
 namespace
 {
 // import unicode string rule
@@ -360,9 +360,13 @@ auto const  bbox_def = lit("\"bbox\"") > lit(':')
     ;
 
 
+// A topology must have an “objects” member whose value is an object.
+// This object may have any number of members, whose value must be a geometry object.
 auto const objects_def = lit("\"objects\"") > lit(':')
     > lit('{')
-    > ((omit[*~char_(':')] > lit(':') > ((geometry_collection[push_collection] | geometry[push_geometry]))) % lit(','))
+    > -((omit[json_string] > ':' > ( geometry_collection[push_collection]
+                                   | geometry[push_geometry]
+                                   )) % ',')
     > lit('}')
     ;
 
@@ -375,7 +379,7 @@ auto const geometry_tuple_def =
      |
      properties[assign_properties]
      |
-     omit[json_string] > lit(':') > omit[json_value]) % lit(',')
+     (omit[json_string] > lit(':') > omit[json_value])) % lit(',')
     ;
 
 auto const geometry_def = lit("{") > geometry_tuple[create_geometry] > lit("}");

test/unit/datasource/topojson.cpp

@@ -29,8 +29,12 @@
 #include <mapnik/json/topojson_grammar_x3.hpp>
 #include <mapnik/json/topojson_utils.hpp>
 
+#define HEREDOC(...) #__VA_ARGS__
+
 namespace {
 
+bool parse_topology_string(std::string const& buffer, mapnik::topojson::topology & topo);
+
 bool parse_topology(std::string const& filename, mapnik::topojson::topology & topo)
 {
     mapnik::util::file file(filename);
@@ -38,6 +42,17 @@ bool parse_topology(std::string const& filename, mapnik::topojson::topology & to
     buffer.resize(file.size());
     std::fread(&buffer[0], buffer.size(), 1, file.get());
     if (!file) return false;
+    return parse_topology_string(buffer, topo);
+}
+
+bool parse_topology_string(std::string const& buffer)
+{
+    mapnik::topojson::topology topo;
+    return parse_topology_string(buffer, topo);
+}
+
+bool parse_topology_string(std::string const& buffer, mapnik::topojson::topology & topo)
+{
     using space_type = boost::spirit::x3::standard::space_type;
     char const* itr = buffer.c_str();
     char const* end = itr + buffer.length();
@@ -50,7 +65,17 @@ bool parse_topology(std::string const& filename, mapnik::topojson::topology & to
         std::cerr << "failed to parse TopoJSON..." << std::endl;
         std::cerr << ex.what() << std::endl;
         std::cerr << "Expected: " << ex.which();
-        std::cerr << " Got: \"" << std::string(ex.where(), ex.where() + 200) << "...\"" << std::endl;
+        std::cerr << "\nGot: \"";
+        auto ctx = ex.where();
+        std::streamsize len = 0;
+        // stop before NUL terminator or after 200 bytes, whichever comes first
+        for (; ctx[len] && len < 200; ++len)
+            ;
+        // extend to UTF-8 character boundary or 210 bytes, whichever comes first
+        for (; len < 210 && ((unsigned char)ctx[len] & 0xC0) == 0x80; ++len)
+            ;
+        std::cerr.write(ctx, len);
+        std::cerr << (ctx[len] ? "..." : "") << '"' << std::endl;
         return false;
     }
     return (itr == end);
@@ -58,8 +83,44 @@ bool parse_topology(std::string const& filename, mapnik::topojson::topology & to
 
 }
 
-TEST_CASE("topojson")
+TEST_CASE("TopoJSON")
 {
+    SECTION("Minimal Topology")
+    {
+        // + A topology must have a member with the name “objects” whose value is another object.
+        // + A topology must have a member with the name “arcs” whose value is an array of arcs.
+        CHECK(parse_topology_string(HEREDOC(
+              {
+                  "type": "Topology", "objects": {}, "arcs": []
+              }
+              )));
+        CHECK(parse_topology_string(HEREDOC(
+              {
+                  "type": "Topology", "arcs": [], "objects": {}
+              }
+              )));
+        CHECK(parse_topology_string(HEREDOC(
+              {
+                  "objects": {}, "type": "Topology", "arcs": []
+              }
+              )));
+        CHECK(parse_topology_string(HEREDOC(
+              {
+                  "objects": {}, "arcs": [], "type": "Topology"
+              }
+              )));
+        CHECK(parse_topology_string(HEREDOC(
+              {
+                  "arcs": [], "type": "Topology", "objects": {}
+              }
+              )));
+        CHECK(parse_topology_string(HEREDOC(
+              {
+                  "arcs": [], "objects": {}, "type": "Topology"
+              }
+              )));
+    }
+
     SECTION("geometry parsing")
     {
         mapnik::value_integer feature_id = 0;