#393 opening datasets errors handling

cate/core/ds.py

@@ -81,7 +81,6 @@
 import glob
 from abc import ABCMeta, abstractmethod
 from math import ceil, sqrt
-import sys
 from typing import Sequence, Optional, Union, Tuple, Any
 
 import xarray as xr
@@ -463,16 +462,14 @@ class DataAccessError(Exception):
     """
     Exceptions produced by Cate's data stores and data sources instances, used to report any problems handling data.
     """
-    def __init__(self, cause, *args, **kwargs):
-        if isinstance(cause, Exception):
-            super(DataAccessError, self).__init__(str(cause), *args, **kwargs)
-            _, _, traceback = sys.exc_info()
-            self.with_traceback(traceback)
-        elif isinstance(cause, str):
-            super(DataAccessError, self).__init__(cause, *args, **kwargs)
+    def __init__(self, source, cause, *args, **kwargs):
+        if isinstance(source, DataSource) or isinstance(source, DataStore):
+            if isinstance(cause, Exception):
+                super(DataAccessError, self).__init__("{}: {}".format(source, str(cause)), *args, **kwargs)
+            elif isinstance(cause, str):
+                super(DataAccessError, self).__init__("{}: {}".format(source, cause), *args, **kwargs)
         else:
-            super(DataAccessError, self).__init__(*args, **kwargs)
-        self._cause = cause
+            super(DataAccessError, self).__init__(self, cause, *args, **kwargs)
 
     @property
     def cause(self):

cate/ds/local.py

@@ -176,7 +176,11 @@ def open_dataset(self,
             except OSError as e:
                 raise IOError("Files: {} caused:\nOSError({}): {}".format(paths, e.errno, e.strerror))
         else:
-            return None
+            if time_range:
+                raise DataAccessError(self, "No data sets available for specified time range {}".format(
+                    TimeRangeLike.format(time_range)), paths)
+            else:
+                raise DataAccessError(self, "No data sets available")
 
     @staticmethod
     def _get_harmonized_coordinate_value(attrs: dict, attr_name: str):
@@ -402,12 +406,14 @@ def update_local(self,
 
         time_range = TimeRangeLike.convert(time_range) if time_range else None
 
-        local_store = DATA_STORE_REGISTRY.get_data_store('local')
+        local_store_name = 'local'
+
+        local_store = DATA_STORE_REGISTRY.get_data_store(local_store_name)
         if not local_store:
             add_to_data_store_registry()
-            local_store = DATA_STORE_REGISTRY.get_data_store('local')
+            local_store = DATA_STORE_REGISTRY.get_data_store(local_store_name)
         if not local_store:
-            raise ValueError('Cannot initialize `local` DataStore')
+            raise ValueError('Cannot initialize `{}` DataStore'.format(local_store_name))
 
         data_sources = local_store.query(ds_id=local_id)  # type: Sequence['DataSource']
         data_source = next((ds for ds in data_sources if isinstance(ds, LocalDataSource) and
@@ -752,8 +758,7 @@ def create_data_source(self, data_source_id: str, region: PolygonLike.TYPE = Non
                             data_source = ds
                             data_source.set_completed(False)
                             break
-                raise DataAccessError("Local data store '{}' already contains a data source named '{}'".
-                                      format(self.id, data_source_id))
+                raise DataAccessError(self, "Data source '{}' already exists.". format(data_source_id))
         if not data_source:
             data_source = LocalDataSource(data_source_id, files=[], data_store=self, spatial_coverage=region,
                                           variables=var_names, temporal_coverage=time_range, meta_info=meta_info)

test/ds/test_local.py

@@ -5,7 +5,7 @@
 import unittest.mock
 import datetime
 import shutil
-from cate.core.ds import DATA_STORE_REGISTRY
+from cate.core.ds import DATA_STORE_REGISTRY, DataAccessError
 from cate.core.types import PolygonLike, TimeRangeLike, VarNamesLike
 from cate.ds.local import LocalDataStore, LocalDataSource
 from cate.ds.esa_cci_odp import EsaCciOdpDataStore
@@ -47,10 +47,10 @@ def test_add_pattern(self):
         data_sources = self.data_store.query()
         self.assertEqual(len(data_sources), 3)
 
-        with self.assertRaises(ValueError) as cm:
+        with self.assertRaises(DataAccessError) as cm:
             self.data_store.add_pattern("a_name", "a_pat2")
-        self.assertEqual("Local data store 'test' already contains a data source named 'test.{}'".format(new_ds_name),
-                         str(cm.exception))
+        self.assertEqual("{}: Data source '{}.{}' already exists.".format(
+            self.data_store, self.data_store.id, new_ds_name), str(cm.exception))
 
         data_sources = self.data_store.query()
         self.assertEqual(len(data_sources), 3)
@@ -304,9 +304,9 @@ def test_open_dataset(self):
         self.assertIsNotNone(xr)
         self.assertEqual(xr.coords.dims.get('time'), 3)
 
-        xr = ds.open_dataset(time_range=(datetime.datetime(1978, 11, 14),
-                                         datetime.datetime(1978, 11, 15)))
-        self.assertIsNone(xr)
+        with self.assertRaises(DataAccessError):
+            ds.open_dataset(time_range=(datetime.datetime(1978, 11, 14),
+                                        datetime.datetime(1978, 11, 15)))
 
         ds = self._local_data_store.query('local_w_temporal')[0]
 
@@ -319,6 +319,10 @@ def test_open_dataset(self):
         self.assertIsNotNone(xr)
         self.assertEqual(xr.coords.dims.get('time'), 1)
 
+        with self.assertRaises(DataAccessError):
+            ds.open_dataset(time_range=(datetime.datetime(1978, 11, 20),
+                                        datetime.datetime(1978, 11, 21)))
+
     def test_make_local(self):
         data_source = self._local_data_store.query('local_w_temporal')[0]