This blog post explains how I handle a typical bug report for the new OSMF Shortbread tiles. Here, I focus on the “island” seems to be missing from “place_labels” report from SomeoneElse

After verifying that the report is correct, I set up my editor environment. It’s useful to have an environment that syntax highlights Jinja SQL files, as well as other files. I use a Visual Studio Code-based editor with the Better Jinja plugin.

The issue is in the place_labels layer. After checking Shortbread, I see that place=island should show at zoom 10 or higher, so there is a bug. Tilekiln creates tiles by reading definitions from shortbread.yaml, so I check there for the place_labels definition.

place_labels:
    description: Holds label points for populated places.
    fields:
        kind: Value of OSM place tag
        name: *name
        name_en: *name_en
        name_de: *name_de
        population: Value of OSM population tag
    sql:
    - minzoom: 4
        maxzoom: 14
        file: shortbread_original/place_labels.04-14.sql.jinja2

This file shows that for zooms 4 to 14, the SQL for the layer is in shortbread_original/place_labels.04-14.sql.jinja2. Since this file is in shortbread_original, osm2pgsql-themepark created it, and it remains unchanged.

SELECT
        ST_AsMVTGeom(geom, {{unbuffered_bbox}}, {{extent}}, {{buffer}}) AS way,
        name,
        name_de,
        name_en,
        kind,
        population
    FROM place_labels
    WHERE geom && {{bbox}}
        AND {{zoom}} >= minzoom
    ORDER BY population desc

There aren’t any obvious bugs in the SQL. There’s no filtering out of islands, so either the data isn’t making it into the place_labels table or it has the wrong zoom. The data is loaded by osm2pgsql, and shortbread.lua tells osm2pgsql how to do that.

themepark:add_topic('shortbread/places')

With this line shortbread.lua loads the shortbread/places topic. This topic is in the themes/shortbread/topics/places.lua file, and in this case the file comes from osm2pgsql-themepark. When reading the file, I see that place=island is being handled, so I go to the database to find an example.

I keep Luxembourg loaded in my database, and Overpass Turbo lets me find way 1010337745 as an example. By running a query, I can find if the object is in the table. Normally I’d do this with a query like SELECT * FROM place_labels WHERE area_id = 1010337745, but as I type it out, I find there’s no area_id column, but there is node_id.

Looking back at the lua, I see the table is defined as a ‘node’ table, so it doesn’t have data from ways loaded. Most place=island are areas, so this is the problem. I need to define the table similar to the address table, where an object could be a node, way, or relation.

The pull request has all the details on how I solved this. I changed the table to accept any object type and functions to process both nodes and areas. In both cases, the code adds a label point to the table. Because this changes the tables, I’m not merging it right away as I want to make other changes before merging and reloading the database on the OSMF servers.