do not convert multiline to multipolygon if one of the part failed, also consider case of 3 vertices line with first and last vertex identical

Author: 3nids

src/core/qgsgeometry.cpp

@@ -6227,9 +6227,10 @@ QgsGeometry* QgsGeometry::convertToPolygon( bool destMultipart )
         for ( QgsMultiPolyline::iterator multiLineIt = multiLine.begin(); multiLineIt != multiLine.end(); ++multiLineIt )
         {
           // do not create polygon for a 1 segment line
-          // this does not consider the special case where line has 2 segments with first and last node identical
           if (( *multiLineIt ).count() < 3 )
-            continue;
+            return 0;
+          if (( *multiLineIt ).count() == 3 && ( *multiLineIt ).first() == ( *multiLineIt ).last() )
+            return 0;
 
           // add closing node
           if (( *multiLineIt ).first() != ( *multiLineIt ).last() )
@@ -6256,21 +6257,23 @@ QgsGeometry* QgsGeometry::convertToPolygon( bool destMultipart )
         QgsPolyline line = asPolyline();
 
         // do not create polygon for a 1 segment line
-        if ( line.count() >= 3 )
-        {
-          // add closing node
-          if ( line.first() != line.last() )
-            line << line.first();
+        if ( line.count() < 3 )
+          return 0;
+        if ( line.count() == 3 && line.first() == line.last() )
+          return 0;
 
-          // destination is multipart
-          if ( destMultipart )
-          {
-            return fromMultiPolygon( QgsMultiPolygon() << ( QgsPolygon() << line ) );
-          }
-          else
-          {
-            return fromPolygon( QgsPolygon() << line );
-          }
+        // add closing node
+        if ( line.first() != line.last() )
+          line << line.first();
+
+        // destination is multipart
+        if ( destMultipart )
+        {
+          return fromMultiPolygon( QgsMultiPolygon() << ( QgsPolygon() << line ) );
+        }
+        else
+        {
+          return fromPolygon( QgsPolygon() << line );
         }
       }
       return 0;

tests/src/python/test_qgsgeometry.py

@@ -1194,7 +1194,7 @@ def testConvertToType(self):
         ######## TO LINE ########
         # POINT TO LINE
         point = QgsGeometry.fromPoint(QgsPoint(1,1))
-        assert point.convertToType(QGis.Line, False) !=0 , "convertToType with a point should return a null geometry"
+        assert point.convertToType(QGis.Line, False) is None , "convertToType with a point should return a null geometry"
         # MULTIPOINT TO LINE
         multipoint = QgsGeometry.fromMultiPoint(points[0][0])
         wkt = multipoint.convertToType(QGis.Line, False).exportToWkt()
@@ -1258,6 +1258,12 @@ def testConvertToType(self):
         wkt = line.convertToType(QGis.Polygon, False).exportToWkt()
         expWkt = "POLYGON((0 0,1 0,1 1,2 1,2 2,0 2,0 0))"
         assert compareWkt( expWkt, wkt ), "convertToType failed: from line to polygon. Expected:\n%s\nGot:\n%s\n" % (expWkt, wkt )
+        # LINE ( 3 vertices, with first = last ) TO POLYGON
+        line = QgsGeometry.fromPolyline([QgsPoint(1,1),QgsPoint(0,0),QgsPoint(1,1)])
+        assert line.convertToType(QGis.Polygon, False) is None , "convertToType to polygon of a 3 vertices lines with first and last vertex identical should return a null geometry"
+        # MULTILINE ( with a part of 3 vertices, with first = last ) TO MULTIPOLYGON
+        multiline = QgsGeometry.fromMultiPolyline([points[0][0],[QgsPoint(1,1),QgsPoint(0,0),QgsPoint(1,1)]])
+        assert multiline.convertToType(QGis.Polygon, True) is None , "convertToType to polygon of a 3 vertices lines with first and last vertex identical should return a null geometry"
         # LINE TO MULTIPOLYGON
         line = QgsGeometry.fromPolyline(points[0][0])
         wkt = line.convertToType(QGis.Polygon, True).exportToWkt()