Handle case when postgis returns NaN for a region area; passing warnings from backend to frontend

web/app/borders_api.py

@@ -298,11 +298,14 @@ def split():
             new_ids.append(free_id)
             counter += 1
             free_id -= 1
+        warnings = []
         for border_id in new_ids:
-            update_border_mwm_size_estimation(g.conn, border_id)
+            try:
+                update_border_mwm_size_estimation(g.conn, border_id)
+            except Exception as e:
+                warnings.append(str(e))
         g.conn.commit()
-
-    return jsonify(status='ok')
+    return jsonify(status='ok', warnings=warnings)
 
 @app.route('/join')
 def join_borders():
@@ -442,9 +445,13 @@ def copy_from_osm():
         """, (osm_id,)
     )
     assign_region_to_lowerst_parent(osm_id)
-    update_border_mwm_size_estimation(g.conn, osm_id)
+    warnings = []
+    try:
+        update_border_mwm_size_estimation(g.conn, osm_id)
+    except Exception as e:
+        warnings.append(str(e))
     g.conn.commit()
-    return jsonify(status='ok')
+    return jsonify(status='ok', warnings=warnings)
 
 @app.route('/rename')
 def set_name():
@@ -864,10 +871,14 @@ def chop_largest_or_farthest():
                 GROUP BY name, disabled)
             ) x"""
     )
+    warnings = []
     for border_id in (free_id1, free_id2):
-        update_border_mwm_size_estimation(g.conn, border_id)
+        try:
+            update_border_mwm_size_estimation(g.conn, border_id)
+        except Exception as e:
+            warnings.append(str(e))
     g.conn.commit()
-    return jsonify(status='ok')
+    return jsonify(status='ok', warnings=warnings)
 
 @app.route('/hull')
 def draw_hull():
@@ -1608,7 +1619,7 @@ def border():
 @app.route('/start_over')
 def start_over():
     try:
-        create_countries_initial_structure(g.conn)
+        warnings = create_countries_initial_structure(g.conn)
     except CountryStructureException as e:
         return jsonify(status=str(e))
 
@@ -1616,7 +1627,7 @@ def start_over():
     cursor = g.conn.cursor()
     cursor.execute(f"DELETE FROM {autosplit_table}")
     g.conn.commit()
-    return jsonify(status='ok')
+    return jsonify(status='ok', warnings=warnings[:10])
 
 
 if __name__ == '__main__':

web/app/countries_structure.py

@@ -136,7 +136,7 @@ unilevel_countries = {
             'Panama',
             'Papua New Guinea',
             'Peru', #  need split-merge
-            'Philippines',  # split at level 3 and merge or not merte
+            'Philippines',  # split at level 3 and merge or not merge
             'Qatar',
             'Romania', #  need split-merge
             'Rwanda',
@@ -331,8 +331,13 @@ def _make_country_structure(conn, country_osm_id):
                                              admin_level, regions)
             _create_regions(conn, subregion_ids, regions)
             prev_region_ids = subregion_ids
+    warning = None
     if len(regions) == 1:
-        update_border_mwm_size_estimation(conn, country_osm_id)
+        try:
+            update_border_mwm_size_estimation(conn, country_osm_id)
+        except Exception as e:
+            warning = str(e)
+    return warning
 
 
 def create_countries_initial_structure(conn):
@@ -348,9 +353,13 @@ def create_countries_initial_structure(conn):
         #    ({','.join(f"'{c}'" for c in country_initial_levels.keys())})
         #"""
     )
+    warnings = []
     for rec in cursor:
-        _make_country_structure(conn, rec[0])
+        warning = _make_country_structure(conn, rec[0])
+        if warning:
+            warnings.append(warning)
     conn.commit()
+    return warnings
 
 def get_osm_border_name_by_osm_id(conn, osm_id):
     cursor = conn.cursor()

web/app/static/borders.js

@@ -136,8 +136,11 @@ function makeAnswerHandler(on_ok_func) {
 	return function(answer) {
 		if (answer.status !== 'ok')
 			alert(answer.status);
-		else
+		else {
+		    if (answer.warnings && answer.warnings.length)
+		        alert(answer.warnings.join('\n'));
 			on_ok_func(answer);
+		}
 	};
 }
 

web/app/subregions.py

@@ -1,3 +1,5 @@
+import math
+
 import config
 from mwm_size_predictor import MwmSizePredictor
 
@@ -105,12 +107,14 @@ def update_border_mwm_size_estimation(conn, border_id):
     table = config.TABLE
     cursor = conn.cursor()
     cursor.execute(f"""
-        SELECT ST_Area(geography(geom))/1.0E+6 area
+        SELECT name, ST_Area(geography(geom))/1.0E+6 area
         FROM {table}
         WHERE id = %s""", (border_id, ))
-    rec = cursor.fetchone()
+    name, area = cursor.fetchone()
+    if math.isnan(area):
+        raise Exception(f"Area is NaN for border '{name}' ({border_id})")
     border_data = {
-        'area': rec[0],
+        'area': area,
         'urban_pop': 0,
         'city_cnt': 0,
         'hamlet_cnt': 0