fix(duckpipe): keep web choropleths polygonal after GDAL rounding - #10
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GDAL's COORDINATE_PRECISION collapses islands smaller than the grid into degenerate points/linestrings and wraps the feature in a GeometryCollection (nested for Nouvelle-Aquitaine), which the webapp cannot render: the region showed as 'no data' despite having aggregated scores. Repair written GeoJSON by rebuilding Polygon/MultiPolygon from the polygonal parts and dropping collapse artifacts, and guard all published choropleth layers in the e2e test.
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Problème
Sur la carte « Qualité de vie », la Nouvelle-Aquitaine s'affichait « Pas de donnée » alors que ses agrégats régionaux sont corrects (
stats/regions.json: score_median 0.437, 2457 communes scorées).Cause racine
L'option
COORDINATE_PRECISIONpassée au driver GeoJSON de GDAL dans_copy_geojsonarrondit les coordonnées à l'écriture : les îles plus petites que la grille s'effondrent en Point/LineString dégénérés et GDAL emballe la feature dans uneGeometryCollection. Sur le run publié 2026-07-08 : 3 régions (52, 75, 76), 26 départements en low, 21 en mid. Seule la Nouvelle-Aquitaine avait une collection doublement imbriquée que le front ne rend pas du tout.Correctif
Réparation post-écriture dans
_copy_geojson(entonnoir unique de tous les GeoJSON web) : reconstruction de Polygon/MultiPolygon à partir des parties polygonales, artefacts d'effondrement écartés.L'alternative « pré-arrondi SQL » (
ST_ReducePrecision+ST_CollectionExtract) a été testée et rejetée : elle vide la géométrie de 7 communes réelles à la précision mid (dont Saint-Jean-Cap-Ferrat).Tests
tests/test_publish_web.py: repro déterministe du collapse GDAL (carré + île sous la grille), cas réel de collection imbriquée, contrats de réparation.Validé en rejouant l'export sur le
regions-1000m.geojsonEtalab réel : plus aucune GeometryCollection, la région 75 redevient un MultiPolygon de 755 points.