[OGR provider] Fix issue when writing a multi-part multipolygon in a shapefile with GDAL >= 3.7 (fixes #54537)

rouault · nyalldawson · commit 493219c7cbd8 · 2023-09-29T18:10:33.000+10:00
diff --git a/src/core/providers/ogr/qgsogrprovider.cpp b/src/core/providers/ogr/qgsogrprovider.cpp
@@ -1364,6 +1364,15 @@ OGRGeometryH QgsOgrProvider::ConvertGeometryIfNecessary( OGRGeometryH hGeom )
     return OGR_G_ForceToMultiLineString( hGeom );
   }
 
+  if ( flattenLayerGeomType == wkbPolygon && flattenGeomType == wkbMultiPolygon &&
+       mGDALDriverName == QLatin1String( "ESRI Shapefile" ) )
+  {
+    // Do not force multipolygon to polygon for shapefiles, otherwise it will
+    // cause issues with GDAL 3.7 that does honour the topological intent of
+    // multipolygon
+    return hGeom;
+  }
+
   return OGR_G_ForceTo( hGeom, layerGeomType, nullptr );
 }
 
diff --git a/tests/src/python/test_provider_shapefile.py b/tests/src/python/test_provider_shapefile.py
@@ -1111,6 +1111,24 @@ def testLayersOnSameOGRLayerWithAndWithoutFilter(self):
         assert QgsGeometry.compare(vl3_extent.asPolygon()[0], reference.asPolygon()[0],
                                    0.00001), f'Expected {reference.asWkt()}, got {vl3_extent.asWkt()}'
 
+    def testWritingMultiPolygon(self):
+        """Test that a MultiPolygon written to a Shape Polygon layer doesn't get converted to Polygon"""
+
+        tmpfile = os.path.join(self.basetestpath, 'testWritingMultiPolygon.shp')
+        ds = osgeo.ogr.GetDriverByName('ESRI Shapefile').CreateDataSource(tmpfile)
+        ds.CreateLayer('testWritingMultiPolygon', geom_type=osgeo.ogr.wkbPolygon)
+        ds = None
+
+        vl = QgsVectorLayer(tmpfile, 'test')
+        f = QgsFeature()
+        f.setAttributes([200])
+        wkt = "MultiPolygon (((0 0, 0 1, 1 1, 0 0)),((10 0, 10 1, 11 1, 10 0)))"
+        f.setGeometry(QgsGeometry.fromWkt(wkt))
+        vl.dataProvider().addFeatures([f])
+
+        f = next(vl.getFeatures())
+        self.assertEqual(f.geometry().constGet().asWkt(), wkt)
+
 
 if __name__ == '__main__':
     unittest.main()

Original file line number	Diff line number	Diff line change
`@@ -1364,6 +1364,15 @@ OGRGeometryH QgsOgrProvider::ConvertGeometryIfNecessary( OGRGeometryH hGeom )`
`1364`	`1364`	`return OGR_G_ForceToMultiLineString( hGeom );`
`1365`	`1365`	`}`
`1366`	`1366`
	`1367`	`+ if ( flattenLayerGeomType == wkbPolygon && flattenGeomType == wkbMultiPolygon &&`
	`1368`	`+ mGDALDriverName == QLatin1String( "ESRI Shapefile" ) )`
	`1369`	`+ {`
	`1370`	`+ // Do not force multipolygon to polygon for shapefiles, otherwise it will`
	`1371`	`+ // cause issues with GDAL 3.7 that does honour the topological intent of`
	`1372`	`+ // multipolygon`
	`1373`	`+ return hGeom;`
	`1374`	`+ }`
	`1375`	`+`
`1367`	`1376`	`return OGR_G_ForceTo( hGeom, layerGeomType, nullptr );`
`1368`	`1377`	`}`
`1369`	`1378`