Merge pull request #9 from nens/casper-geometryfilesource

Implement columns attribute for GeometryFileSource

CHANGES.rst

@@ -15,6 +15,9 @@ Changelog of dask-geomodeling
   When taking the difference of a geometry with a missing geometry (A - None),
   geopandas < 0.6 returned A as result, while >= 0.6 returns None as result.
 
+
+- Implemented the 'columns' attribute for GeometryFileSource.
+
 - Fixed the projection attribute of elementwise raster blocks in case one of
   the arguments is a number and not a Block instance.
 

dask_geomodeling/geometry/sources.py

@@ -1,12 +1,20 @@
 """
 Module containing geometry sources.
 """
+import fiona
 import geopandas as gpd
 
 from dask import config
 from dask_geomodeling import utils
 from .base import GeometryBlock
 
+# this import is a copy from geopandas.io.files
+try:
+    from fiona import Env as fiona_env
+except ImportError:
+    from fiona import drivers as fiona_env
+
+
 __all__ = ["GeometryFileSource"]
 
 
@@ -54,7 +62,10 @@ def path(self):
 
     @property
     def columns(self):
-        raise NotImplementedError()
+        # this is exactly how geopandas determines the columns
+        with fiona_env(), fiona.open(self.path) as reader:
+            properties = reader.meta["schema"]["properties"]
+            return set(properties.keys()) | {"geometry"}
 
     def get_sources_and_requests(self, **request):
         # check the filters: this block does not support lookups

dask_geomodeling/tests/test_geometry.py

@@ -121,6 +121,9 @@ def test_attr(self):
         self.assertEqual(self.source.path, self.abspath)
         self.assertEqual(self.source.id_field, self.id_field)
 
+    def test_columns(self):
+        self.assertSetEqual(self.source.columns, {"id", "name", "geometry"})
+
     def test_get_data(self):
         result = self.source.get_data(geometry=box(*self.bbox), projection="EPSG:4326")
         self.assertEqual(self.projection, result["projection"])