Test MML queries are valid in CI

.editorconfig

@@ -18,3 +18,7 @@ indent_size = 4
 [*.svg]
 indent_style = undef
 indent_size = undef
+
+# Lastmod files are used by the scripts and should not contain newlines
+[*.lastmod]
+insert_final_newline = false

.github/workflows/ci.yml

@@ -35,7 +35,7 @@ jobs:
     steps:
     - uses: actions/checkout@v3
     - name: Install osm2pgsql and database
-      run: sudo apt-get install -qq --no-install-recommends osm2pgsql postgresql-14-postgis-3
+      run: sudo apt-get install -qq --no-install-recommends osm2pgsql postgresql-14-postgis-3 gdal-bin
     - name: Wait for database
       run : sudo pg_ctlcluster 14 main start; until pg_isready; do sleep 0.5; done
     - name: Setup database
@@ -45,3 +45,7 @@ jobs:
         osm2pgsql -G --hstore --style openstreetmap-carto.style --tag-transform-script openstreetmap-carto.lua -d gis -r xml <(echo '<osm version="0.6"/>')
     - name: Create indexes
       run: psql -1Xq -v ON_ERROR_STOP=1 -d gis -f indexes.sql
+    - name: Load empty shapefiles
+      run: scripts/get-external-data.py --no-update --cache -D scripts/empty_files
+    - name: Test queries are valid
+      run: scripts/test-queries.py project.mml

scripts/empty_files/antarctica-icesheet-outlines-3857.zip.lastmod

@@ -0,0 +1 @@
+Thu, 01 Jan 1970 00:00:00 GMT

scripts/empty_files/antarctica-icesheet-polygons-3857.zip.lastmod

@@ -0,0 +1 @@
+Thu, 01 Jan 1970 00:00:00 GMT

scripts/empty_files/ne_110m_admin_0_boundary_lines_land.zip.lastmod

@@ -0,0 +1 @@
+Thu, 01 Jan 1970 00:00:00 GMT

scripts/empty_files/simplified-water-polygons-split-3857.zip.lastmod

@@ -0,0 +1 @@
+Thu, 01 Jan 1970 00:00:00 GMT

scripts/empty_files/water-polygons-split-3857.zip.lastmod

@@ -0,0 +1 @@
+Thu, 01 Jan 1970 00:00:00 GMT

scripts/test-queries.py

@@ -0,0 +1,84 @@
+#!/usr/bin/env python3
+""""
+Tests the queries in a CartoCSS MML file against a database.
+
+Ignore database settings in the MML file.
+"""
+import argparse
+import logging
+import psycopg2
+import yaml
+
+EMPTY_POLYGON="""ST_SetSRID('POLYGON EMPTY'::geometry, 3857)"""
+
+class ResultHasRowsError(Exception):
+    """Class for layers that have """
+    pass
+
+def testLayer(layer, curs):
+    datasource = layer["Datasource"]
+    if datasource["type"] != "postgis":
+        logging.warning("Layer type {} not supported".format(layer["type"]))
+        return
+    geometry_field=datasource["geometry_field"]
+
+    full_query = """
+    SELECT "{}" FROM
+    {}
+    """.format(geometry_field, datasource["table"])
+    if "!bbox!" not in full_query:
+        full_query += "\nWHERE {} && !bbox!".format(geometry_field)
+
+    query = full_query.replace("!bbox!", EMPTY_POLYGON).replace("!pixel_width!", "0").replace("!pixel_height!", "0").replace("!scale_denominator!", "0")
+    logging.debug("Running query {}".format(query))
+    curs.execute(query)
+    if curs.rowcount != 0:
+        raise ResultHasRowsError(query)
+
+def main():
+    # parse options
+    parser = argparse.ArgumentParser(
+             description="Test CartoCSS project queries against a database")
+
+
+    parser.add_argument("-d", "--database", action="store", default="gis",
+                        help="Override database name to connect to")
+    parser.add_argument("-H", "--host", action="store",
+                        help="Override database server host or socket directory")
+    parser.add_argument("-p", "--port", action="store",
+                        help="Override database server port")
+    parser.add_argument("-U", "--username", action="store",
+                        help="Override database user name")
+    parser.add_argument("-v", "--verbose", action="store_true",
+                        help="Be more verbose. Overrides -q")
+    parser.add_argument("-q", "--quiet", action="store_true",
+                        help="Only report serious problems")
+    parser.add_argument("-w", "--password", action="store",
+                        help="Override database password")
+
+    parser.add_argument('project', type=argparse.FileType('r'),
+                        help="CartoCSS MML file")
+    opts = parser.parse_args()
+
+    if opts.verbose:
+        logging.basicConfig(level=logging.DEBUG)
+    elif opts.quiet:
+        logging.basicConfig(level=logging.WARNING)
+    else:
+        logging.basicConfig(level=logging.INFO)
+
+    mml=yaml.safe_load(opts.project)
+    logging.debug("Loaded MML")
+
+    with psycopg2.connect(database=opts.database, host=opts.host,
+                          port=opts.port, user=opts.username,
+                          password=opts.password).cursor() as curs:
+        curs.execute("SET default_transaction_read_only = TRUE;")
+        for layer in mml["Layer"]:
+            testLayer(layer, curs)
+
+
+
+
+if __name__ == '__main__':
+    main()