Make transformation exceptions more comprehensible (#60)

CHANGES.rst

@@ -4,6 +4,8 @@ Changelog of dask-geomodeling
 2.2.11 (unreleased)
 -------------------
 
+- Make transformation exceptions more comprehensible.
+
 - Check for matching time resolutions in raster.Clip.
 
 - Added 'product' to raster.reduction STATISTICS.

dask_geomodeling/tests/test_utils.py

@@ -199,6 +199,13 @@ def test_shapely_transform(self):
         box4326 = utils.shapely_transform(box28992, src_srs=src_srs, dst_srs=dst_srs)
         assert_almost_equal((5.4, 52.0), list(box4326.centroid.coords)[0], decimal=1)
 
+    def test_shapely_transform_invalid(self):
+        src_srs = "EPSG:4326"
+        dst_srs = "EPSG:28992"
+        box4326 = geometry.box(100000, 400000, 200000, 500000)
+        with pytest.raises(utils.TransformException):
+            utils.shapely_transform(box4326, src_srs=src_srs, dst_srs=dst_srs)
+
     @mock.patch("dask_geomodeling.utils.shapely_transform")
     def test_min_size_transform(self, shapely_transform):
         min_size = 100

dask_geomodeling/utils.py

@@ -410,6 +410,12 @@ def crs_to_srs(crs):
         return crs.to_string()
 
 
+class TransformException(Exception):
+    """Exception used for errors occuring while transforming between spatial
+    reference systems"""
+    pass
+
+
 def wkb_transform(wkb, src_sr, dst_sr):
     """
     Return a shapely geometry transformed from src_sr to dst_sr.
@@ -434,9 +440,24 @@ def shapely_transform(geometry, src_srs, dst_srs):
     Note that we do not use geopandas for the transformation, because this is
     much slower than OGR.
     """
-    return shapely_wkb.loads(
-        wkb_transform(geometry.wkb, src_sr=get_sr(src_srs), dst_sr=get_sr(dst_srs))
-    )
+    transform_kwargs = {
+        "wkb": geometry.wkb,
+        "src_sr": get_sr(src_srs),
+        "dst_sr": get_sr(dst_srs),
+    }
+    try:
+        output_wkb = wkb_transform(**transform_kwargs)
+    except RuntimeError:
+        # include the geometry in the error message, truncated to 64 chars
+        wkt = geometry.wkt
+        if len(wkt) > 64:
+            wkt = wkt[:61] + "..."
+        raise TransformException(
+            "An error occured while transforming {} from {} to {}.".format(
+                wkt, src_srs, dst_srs
+            )
+        )
+    return shapely_wkb.loads(output_wkb)
 
 
 def geoseries_transform(df, src_srs, dst_srs):