[OGR provider] Fix issue when writing a multi-part multipolygon in a …

…shapefile with GDAL >= 3.7 (fixes #54537)
qgis · Sep 29, 2023 · 7246983 · 7246983
1 parent 5786239
commit 7246983
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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()