Fix errors and inconsistencies resulting from adding M values to

a dataset with a ****25D wkb type Previously we did not handle adding M values to any "25d" WKB type (as there's no such thing as Point25DM, etc). But being strict like this turns out to be wrong, because it results in corrupted/ inconsistent geometries as a result of calls to QgsAbstractGeometry.addMValue() whenever the original geometry is a 25D type. In this situation, the M values were being added but the WKB type wasn't being updated to reflect this and would remain at the original *25D type. Ultimately, this causes GDAL to reject any wkb generated for the geometries and failures to write features into an output dataset. This is especially the case with GDB files, where the dataset can sometimes be reported as a ZM type while individual features are only 25D types (for whatever archiac reasons!)
qgis · Nov 20, 2020 · 6c30a46 · 6c30a46
1 parent 8f4367d
commit 6c30a46
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Showing 2 changed files with 19 additions and 14 deletions.
diff --git a/src/core/geometry/qgswkbtypes.h b/src/core/geometry/qgswkbtypes.h
@@ -1176,13 +1176,18 @@ class CORE_EXPORT QgsWkbTypes
         return Unknown;
       else if ( type == NoGeometry )
         return NoGeometry;
-      else if ( type == Point25D ||
-                type == LineString25D ||
-                type == Polygon25D ||
-                type == MultiPoint25D ||
-                type == MultiLineString25D ||
-                type == MultiPolygon25D )
-        return type; //can't add M dimension to these types
+      else if ( type == Point25D )
+        return PointZM;
+      else if ( type == LineString25D )
+        return LineStringZM;
+      else if ( type == Polygon25D )
+        return PolygonZM;
+      else if ( type == MultiPoint25D )
+        return MultiPointZM;
+      else if ( type == MultiLineString25D )
+        return MultiLineStringZM;
+      else if ( type == MultiPolygon25D )
+        return MultiPolygonZM;
 
       //upgrade with m dimension
       Type flat = flatType( type );

diff --git a/tests/src/python/test_qgsgeometry.py b/tests/src/python/test_qgsgeometry.py
@@ -3905,13 +3905,13 @@ def testWkbTypes(self):
         self.assertEqual(QgsWkbTypes.addM(QgsWkbTypes.MultiSurfaceM), QgsWkbTypes.MultiSurfaceM)
         self.assertEqual(QgsWkbTypes.addM(QgsWkbTypes.MultiSurfaceZM), QgsWkbTypes.MultiSurfaceZM)
         self.assertEqual(QgsWkbTypes.addM(QgsWkbTypes.NoGeometry), QgsWkbTypes.NoGeometry)
-        # can't be added to these types
-        self.assertEqual(QgsWkbTypes.addM(QgsWkbTypes.Point25D), QgsWkbTypes.Point25D)
-        self.assertEqual(QgsWkbTypes.addM(QgsWkbTypes.LineString25D), QgsWkbTypes.LineString25D)
-        self.assertEqual(QgsWkbTypes.addM(QgsWkbTypes.Polygon25D), QgsWkbTypes.Polygon25D)
-        self.assertEqual(QgsWkbTypes.addM(QgsWkbTypes.MultiPoint25D), QgsWkbTypes.MultiPoint25D)
-        self.assertEqual(QgsWkbTypes.addM(QgsWkbTypes.MultiLineString25D), QgsWkbTypes.MultiLineString25D)
-        self.assertEqual(QgsWkbTypes.addM(QgsWkbTypes.MultiPolygon25D), QgsWkbTypes.MultiPolygon25D)
+        # we force upgrade 25D types to "Z" before adding the M value
+        self.assertEqual(QgsWkbTypes.addM(QgsWkbTypes.Point25D), QgsWkbTypes.PointZM)
+        self.assertEqual(QgsWkbTypes.addM(QgsWkbTypes.LineString25D), QgsWkbTypes.LineStringZM)
+        self.assertEqual(QgsWkbTypes.addM(QgsWkbTypes.Polygon25D), QgsWkbTypes.PolygonZM)
+        self.assertEqual(QgsWkbTypes.addM(QgsWkbTypes.MultiPoint25D), QgsWkbTypes.MultiPointZM)
+        self.assertEqual(QgsWkbTypes.addM(QgsWkbTypes.MultiLineString25D), QgsWkbTypes.MultiLineStringZM)
+        self.assertEqual(QgsWkbTypes.addM(QgsWkbTypes.MultiPolygon25D), QgsWkbTypes.MultiPolygonZM)
 
         # test dropping z dimension from types
         self.assertEqual(QgsWkbTypes.dropZ(QgsWkbTypes.Unknown), QgsWkbTypes.Unknown)