Support parsing DATE columns from Standard SQL tables

Change-Id: Ic979171dfb9d2210334c51a92f8d799cafbff95a

google/cloud/_helpers.py

@@ -379,6 +379,19 @@ def _millis_from_datetime(value):
         return _millis(value)
 
 
+def _date_from_iso8601_date(value):
+    """Convert a ISO8601 date string to native datetime date
+
+    :type value: str
+    :param value: The date string to convert
+
+    :rtype: :class:`datetime.date`
+    :returns: A datetime date object created from the string
+
+    """
+    return datetime.datetime.strptime(value, '%Y-%m-%d').date()
+
+
 def _rfc3339_to_datetime(dt_str):
     """Convert a microsecond-precision timetamp to a native datetime.
 

google/cloud/bigquery/_helpers.py

@@ -15,6 +15,7 @@
 """Shared helper functions for BigQuery API classes."""
 
 from google.cloud._helpers import _datetime_from_microseconds
+from google.cloud._helpers import _date_from_iso8601_date
 
 
 def _not_null(value, field):
@@ -47,6 +48,12 @@ def _datetime_from_json(value, field):
         return _datetime_from_microseconds(1e6 * float(value))
 
 
+def _date_from_json(value, field):
+    """Coerce 'value' to a datetime date, if set or not nullable"""
+    if _not_null(value, field):
+        return _date_from_iso8601_date(value)
+
+
 def _record_from_json(value, field):
     """Coerce 'value' to a mapping, if set or not nullable."""
     if _not_null(value, field):
@@ -71,6 +78,7 @@ def _string_from_json(value, _):
     'FLOAT': _float_from_json,
     'BOOLEAN': _bool_from_json,
     'TIMESTAMP': _datetime_from_json,
+    'DATE': _date_from_json,
     'RECORD': _record_from_json,
     'STRING': _string_from_json,
 }

unit_tests/test__helpers.py

@@ -531,6 +531,17 @@ def test_it(self):
         NOW_MICROS = _microseconds_from_datetime(NOW)
         self.assertEqual(self._callFUT(NOW_MICROS), NOW)
 
+class Test___date_from_iso8601_date(unittest.TestCase):
+
+    def _callFUT(self, value):
+        from google.cloud._helpers import _date_from_iso8601_date
+        return _date_from_iso8601_date(value)
+
+    def test_todays_date(self):
+        import datetime
+        TODAY = datetime.date.today()
+        self.assertEqual(self._callFUT(TODAY.strftime("%Y-%m-%d")), TODAY)
+
 
 class Test__rfc3339_to_datetime(unittest.TestCase):