return None and raise warning when transform_geom dst_ogr_geom is NULL (

#802)
Toblerity · Oct 24, 2019 · d0e94b5 · d0e94b5
1 parent cdd3542
commit d0e94b5
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Showing 2 changed files with 41 additions and 8 deletions.
diff --git a/fiona/_transform.pyx b/fiona/_transform.pyx
@@ -5,6 +5,7 @@
 from __future__ import absolute_import
 
 import logging
+import warnings
 
 from fiona cimport _cpl, _crs, _csl, _geometry
 from fiona._crs cimport OGRSpatialReferenceH
@@ -129,12 +130,10 @@ def _transform_geom(
     cdef void *src_ogr_geom = NULL
     cdef void *dst_ogr_geom = NULL
     cdef int i
-
     if src_crs and dst_crs:
         src = _crs_from_crs(src_crs)
         dst = _crs_from_crs(dst_crs)
         transform = _crs.OCTNewCoordinateTransformation(src, dst)
-
         # Transform options.
         options = _csl.CSLSetNameValue(
                     options, "DATELINEOFFSET", 
@@ -148,10 +147,19 @@ def _transform_geom(
                         <const OGRGeometry *>src_ogr_geom,
                         <OGRCoordinateTransformation *>transform,
                         options)
-        g = _geometry.GeomBuilder().build(dst_ogr_geom)
-
-        _geometry.OGR_G_DestroyGeometry(dst_ogr_geom)
-        _geometry.OGR_G_DestroyGeometry(src_ogr_geom)
+        if dst_ogr_geom == NULL:
+            g = None
+            warnings.warn(
+                "Full reprojection failed, but partial is possible. To enable partial "
+                "reprojection wrap the transform_geom call like so:\n"
+                "with fiona.Env(OGR_ENABLE_PARTIAL_REPROJECTION=True):\n"
+                "    transform_geom(...)"
+            )
+        else:
+            g = _geometry.GeomBuilder().build(dst_ogr_geom)
+            _geometry.OGR_G_DestroyGeometry(dst_ogr_geom)
+        if src_ogr_geom != NULL:
+            _geometry.OGR_G_DestroyGeometry(src_ogr_geom)
         _crs.OCTDestroyCoordinateTransformation(transform)
         if options != NULL:
             _csl.CSLDestroy(options)
@@ -161,8 +169,7 @@ def _transform_geom(
     else:
         g = geom
 
-    if precision >= 0:
-
+    if precision >= 0 and g is not None:
         if g['type'] == 'Point':
             coords = list(g['coordinates'])
             x, y = coords[:2]

diff --git a/tests/test_transform.py b/tests/test_transform.py
@@ -48,3 +48,29 @@
 def test_transform_geom_with_z(geom):
     """Transforming a geom with Z succeeds"""
     g2 = transform.transform_geom("epsg:4326", "epsg:3857", geom, precision=3)
+
+
+def test_transform_geom_null_dest():
+    failed_geom = {
+        'type': 'Polygon',
+        'coordinates': ((
+            (81.2180196471443, 6.197141424988303),
+            (80.34835696810447, 5.968369859232141),
+            (79.87246870312859, 6.763463446474915),
+            (79.69516686393516, 8.200843410673372),
+            (80.14780073437967, 9.824077663609557),
+            (80.83881798698664, 9.268426825391174),
+            (81.3043192890718, 8.564206244333675),
+            (81.78795901889143, 7.523055324733178),
+            (81.63732221876066, 6.481775214051936),
+            (81.2180196471443, 6.197141424988303)
+        ),)
+    }
+    with pytest.warns(UserWarning):
+        assert transform.transform_geom(
+            src_crs="epsg:4326",
+            dst_crs="epsg:32628",
+            geom=failed_geom,
+            antimeridian_cutting=True,
+            precision=2,
+        ) is None