Flex: Allow creating point geometry from way

src/geom-from-osm.cpp

@@ -19,11 +19,18 @@
 
 namespace geom {
 
+void create_point(geometry_t *geom, osmium::Location const &location)
+{
+    if (location.valid()) {
+        auto &point = geom->set<point_t>();
+        point.set_x(location.lon());
+        point.set_y(location.lat());
+    }
+}
+
 void create_point(geometry_t *geom, osmium::Node const &node)
 {
-    auto &point = geom->set<point_t>();
-    point.set_x(node.location().lon());
-    point.set_y(node.location().lat());
+    create_point(geom, node.location());
 }
 
 geometry_t create_point(osmium::Node const &node)

src/geom-from-osm.hpp

@@ -27,6 +27,15 @@
 
 namespace geom {
 
+/**
+ * Create a point geometry from a location. If the location is not valid,
+ * the output will not be changed.
+ *
+ * \param geom Pointer to an existing geometry which will be used as output.
+ * \param location The input location.
+ */
+void create_point(geometry_t *geom, osmium::Location const &location);
+
 /**
  * Create a point geometry from a node.
  *

src/output-flex.cpp

@@ -454,11 +454,46 @@ int output_flex_t::app_get_bbox()
 
 int output_flex_t::app_as_point()
 {
-    check_context_and_state("as_point", "node",
-                            m_calling_context != calling_context::process_node);
+    check_for_object(lua_state(), "as_point");
+
+    if (m_calling_context == calling_context::process_node) {
+        if (lua_gettop(lua_state()) > 1) {
+            throw fmt_error("No parameter(s) needed for as_point().");
+        }
+        auto *geom = create_lua_geometry_object(lua_state());
+        geom::create_point(geom, *m_context_node);
+        return 1;
+    }
+
+    if (m_calling_context != calling_context::process_way) {
+        throw fmt_error(
+            "The function as_point() can only be called (directly "
+            "or indirectly) from the process_[untagged]_node/way() functions.");
+    }
+
+    if (lua_gettop(lua_state()) > 2) {
+        throw fmt_error("Too many arguments for function as_point()");
+    }
+
+    m_way_cache.add_nodes(middle());
+    auto const &nodes = m_way_cache.get().nodes();
+
+    int64_t n = 1; // get first node by default
+    if (lua_gettop(lua_state()) > 1) {
+        if (lua_type(lua_state(), 2) != LUA_TNUMBER) {
+            throw std::runtime_error{
+                "Argument #1 to 'as_point()' must be an integer."};
+        }
+        n = lua_tointeger(lua_state(), 2);
+        if (n < 0) { // negative index values count from the back
+            n += static_cast<int64_t>(nodes.size()) + 1;
+        }
+    }
 
     auto *geom = create_lua_geometry_object(lua_state());
-    geom::create_point(geom, *m_context_node);
+    if (n > 0 && static_cast<std::size_t>(n) <= nodes.size()) {
+        geom::create_point(geom, nodes[n - 1].location());
+    } // fall through returning null geometry if 0 or too large or small
 
     return 1;
 }

tests/bdd/flex/geometry-point.feature

@@ -0,0 +1,95 @@
+Feature: Creating point features from way
+
+    Scenario:
+        Given the grid
+            | 1 | 2 |   |
+            | 4 |   | 3 |
+            |   | 5 |   |
+        And the OSM data
+            """
+            w20 Thighway=motorway Nn1,n2,n3
+            w21 Thighway=motorway Nn4,n5
+            """
+        And the lua style
+            """
+            local points = osm2pgsql.define_way_table('osm2pgsql_test_points', {
+                { column = 'n', type = 'int' },
+                { column = 'geom', type = 'point', projection = 4326, not_null = false },
+            })
+
+            function osm2pgsql.process_way(object)
+                if object.tags.highway == 'motorway' then
+                    points:insert({ n = nil, geom = object:as_point() })
+                    points:insert({ n =   0, geom = object:as_point(0) })
+                    points:insert({ n =   1, geom = object:as_point(1) })
+                    points:insert({ n =   2, geom = object:as_point(2) })
+                    points:insert({ n =   3, geom = object:as_point(3) })
+                    points:insert({ n =   4, geom = object:as_point(4) })
+                    points:insert({ n =  -1, geom = object:as_point(-1) })
+                    points:insert({ n =  -2, geom = object:as_point(-2) })
+                    points:insert({ n =  -3, geom = object:as_point(-3) })
+                end
+            end
+            """
+        When running osm2pgsql flex
+
+        Then table osm2pgsql_test_points contains exactly
+            | way_id | n    | ST_AsText(geom) |
+            | 20     | NULL | 1               |
+            | 20     | 0    | NULL            |
+            | 20     | 1    | 1               |
+            | 20     | 2    | 2               |
+            | 20     | 3    | 3               |
+            | 20     | 4    | NULL            |
+            | 20     | -1   | 3               |
+            | 20     | -2   | 2               |
+            | 20     | -3   | 1               |
+            | 21     | NULL | 4               |
+            | 21     | 0    | NULL            |
+            | 21     | 1    | 4               |
+            | 21     | 2    | 5               |
+            | 21     | 3    | NULL            |
+            | 21     | 4    | NULL            |
+            | 21     | -1   | 5               |
+            | 21     | -2   | 4               |
+            | 21     | -3   | NULL            |
+
+    Scenario:
+        Given the grid
+            | 1 | 2 |
+        And the OSM data
+            """
+            w20 Thighway=motorway Nn1,n2
+            """
+        And the lua style
+            """
+            function osm2pgsql.process_way(object)
+                local geom = object:as_point('foo')
+            end
+            """
+        Then running osm2pgsql flex fails
+
+        And the error output contains
+            """
+            Argument #1 to 'as_point()' must be an integer.
+            """
+
+    Scenario:
+        Given the grid
+            | 1 | 2 |
+        And the OSM data
+            """
+            w20 Thighway=motorway Nn1,n2
+            """
+        And the lua style
+            """
+            function osm2pgsql.process_way(object)
+                local geom = object:as_point(1, 'foo')
+            end
+            """
+        Then running osm2pgsql flex fails
+
+        And the error output contains
+            """
+            Too many arguments for function as_point()
+            """

tests/test-geom-linestrings.cpp

@@ -115,6 +115,50 @@ TEST_CASE("create_linestring from invalid OSM data", "[NoDB]")
     REQUIRE(geom.is_null());
 }
 
+TEST_CASE("create_point from OSM way data", "[NoDB]")
+{
+    test_buffer_t buffer;
+    buffer.add_way("w20 Nn1x1y1,n2x2y2");
+
+    auto const &nodes = buffer.buffer().get<osmium::Way>(0).nodes();
+    geom::geometry_t geom;
+    geom::create_point(&geom, nodes[0].location());
+
+    REQUIRE(geom.is_point());
+    REQUIRE(geometry_type(geom) == "POINT");
+    REQUIRE(dimension(geom) == 0);
+    REQUIRE(num_geometries(geom) == 1);
+    REQUIRE(geom.get<geom::point_t>() == geom::point_t{1, 1});
+}
+
+TEST_CASE("create_point from OSM data without locations", "[NoDB]")
+{
+    test_buffer_t buffer;
+    buffer.add_way("w20 Nn1,n2");
+
+    auto const &nodes = buffer.buffer().get<osmium::Way>(0).nodes();
+    geom::geometry_t geom;
+    geom::create_point(&geom, nodes[0].location());
+
+    REQUIRE(geom.is_null());
+}
+
+TEST_CASE("create_point from way with single node", "[NoDB]")
+{
+    test_buffer_t buffer;
+    buffer.add_way("w20 Nn1x1y1");
+
+    auto const &nodes = buffer.buffer().get<osmium::Way>(0).nodes();
+    geom::geometry_t geom;
+    geom::create_point(&geom, nodes[0].location());
+
+    REQUIRE(geom.is_point());
+    REQUIRE(geometry_type(geom) == "POINT");
+    REQUIRE(dimension(geom) == 0);
+    REQUIRE(num_geometries(geom) == 1);
+    REQUIRE(geom.get<geom::point_t>() == geom::point_t{1, 1});
+}
+
 TEST_CASE("geom::segmentize w/o split", "[NoDB]")
 {
     geom::linestring_t const expected{{0, 0}, {1, 2}, {2, 2}};

tests/test-geom-points.cpp

@@ -42,6 +42,20 @@ TEST_CASE("geom::point_t from location", "[NoDB]")
     REQUIRE(p == geom::point_t{3.141, 2.718});
 }
 
+TEST_CASE("geom::point_t from location with create_point", "[NoDB]")
+{
+    osmium::Location const location{1.1, 2.2};
+
+    geom::geometry_t geom;
+    geom::create_point(&geom, location);
+    REQUIRE(geom.is_point());
+
+    auto const &p = geom.get<geom::point_t>();
+    REQUIRE(p.x() == Approx(1.1));
+    REQUIRE(p.y() == Approx(2.2));
+    REQUIRE(p == geom::point_t{1.1, 2.2});
+}
+
 TEST_CASE("create_point from OSM data", "[NoDB]")
 {
     test_buffer_t buffer;