Fix: Handle special single-geom case for multipoint/linestring

src/geom-from-osm.cpp

@@ -112,16 +112,24 @@ void create_multipoint(geometry_t *geom, osmium::memory::Buffer const &buffer)
             geom->reset();
         }
     } else {
-        auto &multiline = geom->set<multipoint_t>();
+        auto &multipoint = geom->set<multipoint_t>();
         for (auto const &node : nodes) {
             auto const location = node.location();
             if (location.valid()) {
-                multiline.add_geometry(point_t{location});
+                multipoint.add_geometry(point_t{location});
             }
         }
-        if (multiline.num_geometries() == 0) {
+        if (multipoint.num_geometries() == 0) {
             geom->reset();
         }
+
+        // In the (unlikely) event that this multipoint geometry only contains
+        // a single point because locations for all others were not available
+        // turn it into a point geometry retroactively.
+        if (multipoint.num_geometries() == 1) {
+            auto const p = multipoint[0];
+            geom->set<point_t>() = p;
+        }
     }
 }
 
@@ -154,6 +162,15 @@ void create_multilinestring(geometry_t *geom,
         if (multiline.num_geometries() == 0) {
             geom->reset();
         }
+
+        // In the (unlikely) event that this multilinestring geometry only
+        // contains a single linestring because ways or locations for all
+        // others were not available turn it into a linestring geometry
+        // retroactively.
+        if (multiline.num_geometries() == 1 && !force_multi) {
+            auto p = std::move(multiline[0]);
+            geom->set<linestring_t>() = std::move(p);
+        }
     }
 }
 

tests/test-geom-multilinestrings.cpp

@@ -65,6 +65,39 @@ TEST_CASE("create_multilinestring with single line and no force_multi",
     REQUIRE(l == expected);
 }
 
+TEST_CASE(
+    "create_multilinestring with multiple incomplete lines and no force_multi",
+    "[NoDB]")
+{
+    geom::linestring_t const expected{{1, 1}, {2, 1}};
+
+    test_buffer_t buffer;
+
+    SECTION("with second invalid line")
+    {
+        buffer.add_way("w20 Nn10x1y1,n11x2y1");
+        buffer.add_way("w21 Nn12x2y2");
+    }
+
+    SECTION("with second line with missing location")
+    {
+        buffer.add_way("w20 Nn10x1y1,n11x2y1");
+        buffer.add_way("w21 Nn12x2y2,n13");
+    }
+
+    auto const geom =
+        geom::line_merge(geom::create_multilinestring(buffer.buffer(), false));
+
+    REQUIRE(geom.is_linestring());
+    REQUIRE(geometry_type(geom) == "LINESTRING");
+    REQUIRE(num_geometries(geom) == 1);
+    REQUIRE(area(geom) == Approx(0.0));
+    REQUIRE(length(geom) == Approx(1.0));
+    auto const &l = geom.get<geom::linestring_t>();
+    REQUIRE(l.num_geometries() == 1);
+    REQUIRE(l == expected);
+}
+
 TEST_CASE("create_multilinestring with single line forming a ring", "[NoDB]")
 {
     geom::linestring_t const expected{{1, 1}, {2, 1}, {2, 2}, {1, 1}};

tests/test-geom-multipoints.cpp

@@ -95,3 +95,29 @@ TEST_CASE("create_multipoint from OSM data", "[NoDB]")
     REQUIRE(length(geom) == Approx(0.0));
     REQUIRE(centroid(geom) == geom::geometry_t{geom::point_t{2, 1}});
 }
+
+TEST_CASE("create_multipoint from OSM data with only a single point", "[NoDB]")
+{
+    test_buffer_t buffer;
+
+    SECTION("only single node in relation")
+    {
+        buffer.add_node("n10 x1 y0");
+    }
+
+    SECTION("two nodes in relation, but one with missing location")
+    {
+        buffer.add_node("n10 x1 y0");
+        buffer.add_node("n11");
+    }
+
+    auto const geom = geom::create_multipoint(buffer.buffer());
+
+    REQUIRE(geometry_type(geom) == "POINT");
+    REQUIRE(dimension(geom) == 0);
+    REQUIRE(num_geometries(geom) == 1);
+    REQUIRE(geom.get<geom::point_t>() == geom::point_t{1, 0});
+    REQUIRE(area(geom) == Approx(0.0));
+    REQUIRE(length(geom) == Approx(0.0));
+    REQUIRE(centroid(geom) == geom::geometry_t{geom::point_t{1, 0}});
+}