Change Query.to_csv() to use new from_datatest() method

and remove old _to_reader() method along with associated
tests.

datatest/_query/query.py

@@ -976,26 +976,6 @@ def __repr__(self):
         return '{0}({1}{2}{3}){4}'.format(
             class_repr, source_repr, args_repr, kwds_repr, query_steps_repr)
 
-    def _get_reader(self, fieldnames=None):
-        """Return a csv.reader-like iterator of the query results."""
-        iterable = _flatten_data(self.execute())
-        if not nonstringiter(iterable):
-            iterable = [iterable]
-
-        if not fieldnames:
-            first_row, iterable = iterpeek(iterable)
-            if not nonstringiter(first_row):
-                first_row = [first_row]
-
-            if self.args:
-                (fieldnames,) = _flatten_data(self.args[0])
-                if len(first_row) != len(fieldnames):
-                    fieldnames = None
-
-        if fieldnames:
-            iterable = itertools.chain([fieldnames], iterable)
-        return iterable
-
     def to_csv(self, file, fieldnames=None, **fmtparams):
         """Execute the query and write the results as a CSV file
         (dictionaries and other mappings will be seralized).
@@ -1009,7 +989,7 @@ def to_csv(self, file, fieldnames=None, **fmtparams):
         original *columns* argument will be used if the number of
         selected columns matches the number of resulting columns.
         """
-        reader = self._get_reader(fieldnames)
+        reader = get_reader.from_datatest(self)
 
         if not isinstance(file, file_types):
             if PY2:

tests/test_query.py

@@ -1530,94 +1530,6 @@ def test_call(self):
         self.assertEqual(query.fetch(), expected)
 
 
-class TestQueryGetReader(unittest.TestCase):
-    def test_iterable_of_iterables(self):
-        query = Query.from_object([['a', 1], ['b', 2]])
-
-        reader = query._get_reader()
-
-        self.assertEqual(list(reader), [['a', 1], ['b', 2]])
-
-    def test_iterable_of_noniterables(self):
-        query = Query.from_object([1, 2])
-
-        reader = query._get_reader()
-
-        self.assertEqual(list(reader), [1, 2])
-
-    def test_single_noniterable(self):
-        query = Query.from_object(1)
-
-        reader = query._get_reader()
-        self.assertEqual(list(reader), [1])
-
-        reader = query._get_reader('A')
-        self.assertEqual(list(reader), ['A', 1])
-
-        # QUESTION: Should this behavior be implemented?
-        #reader = query._get_reader(['A'])
-        #self.assertEqual(list(reader), ['A', 1])
-
-    def test_automatic_fieldnames(self):
-        select = Selector([['A', 'B'], ['a', 1], ['b', 2]])
-        query = select(['A', 'B'])
-
-        reader = query._get_reader()  # <- Automatic field names.
-        self.assertEqual(list(reader), [['A', 'B'], ['a', 1], ['b', 2]])
-
-        # Because selection contains 2 items, but output has been
-        # mapped to 1 item, it should not output a header.
-        func = lambda x: x[0] + str(x[1])
-        reader = query.map(func)._get_reader()
-        self.assertEqual(list(reader), ['a1', 'b2'])  # <- No header!
-
-    def test_explicit_fieldnames(self):
-        select = Selector([['A', 'B'], ['a', 1], ['b', 2]])
-
-        query = select(['A', 'B'])
-
-        reader = query._get_reader(['X', 'Y'])  # <- Explicit field names.
-        self.assertEqual(list(reader), [['X', 'Y'], ['a', 1], ['b', 2]])
-
-    def test_mapping_of_single_values(self):
-        select = Selector([['A', 'B'], ['a', 1], ['b', 2]])
-        query = select({'A': 'B'})  # <- A mapping!
-
-        reader = query._get_reader()
-
-        self.assertEqual(list(reader), [('A', 'B'), ('a', 1), ('b', 2)])
-
-    def test_mapping_with_tup_keys_and_single_vals(self):
-        select = Selector([['A', 'B'], ['a', 1], ['b', 2]])
-        query = select({('A', 'A'): 'B'})  # <- Tuple keys and single value.
-
-        reader = query._get_reader()
-
-        self.assertEqual(
-            list(reader),
-            [('A', 'A', 'B'), ('a','a', 1), ('b', 'b', 2)]
-        )
-
-    def test_mapping_with_tup_keys_and_tup_vals(self):
-        select = Selector([['A', 'B'], ['a', 1], ['b', 2]])
-        query = select({('A', 'A'): ('B', 'B')})  # <- Tuple keys and values.
-
-        reader = query._get_reader()
-
-        self.assertEqual(
-            list(reader),
-            [('A', 'A', 'B', 'B'), ('a','a', 1, 1), ('b', 'b', 2, 2)]
-        )
-
-    def test_summed_single_value(self):
-        select = Selector([['A', 'B'], ['a', 1], ['b', 2]])
-        query = select('B').sum()
-
-        reader = query._get_reader()
-
-        self.assertEqual(list(reader), ['B', 3])
-
-
 class TestQueryToCsv(unittest.TestCase):
     def setUp(self):
         self.select = Selector([['A', 'B'], ['x', 1], ['y', 2]])