Add fixture case for completely empty "values"; some more xrefs

Author: h-vetinari

pandas/tests/test_strings.py

@@ -90,6 +90,7 @@ def all_string_methods(request):
     ('unicode' if not PY3 else 'string', [u('a'), np.nan, u('c')]),
     ('bytes' if PY3 else 'string', [b'a', np.nan, b'c']),
     ('empty', [np.nan, np.nan, np.nan]),
+    ('empty', []),
     ('mixed-integer', ['a', np.nan, 2]),
     ('mixed', ['a', np.nan, 2.0])]
 ids, _ = zip(*_all_allowed_skipna_inferred_dtypes)  # use inferred type as id
@@ -126,12 +127,13 @@ def all_allowed_skipna_inferred_dtypes(request):
     ('integer', [1, np.nan, 2]),
     ('mixed-integer-float', [1, np.nan, 2.0]),
     ('decimal', [Decimal(1), np.nan, Decimal(2)]),
-    # ('complex', [1 + 1j, np.nan, 2 + 2j]),
     ('boolean', [True, np.nan, False]),
     ('datetime64', [np.datetime64('2013-01-01'), np.nan,
                     np.datetime64('2018-01-01')]),
     ('datetime', [Timestamp('20130101'), np.nan, Timestamp('20180101')]),
     ('date', [date(2013, 1, 1), np.nan, date(2018, 1, 1)]),
+    # The following two dtypes are commented out due to GH 23554
+    # ('complex', [1 + 1j, np.nan, 2 + 2j]),
     # ('timedelta64', [np.timedelta64(1, 'D'),
     #                  np.nan, np.timedelta64(2, 'D')]),
     ('timedelta', [timedelta(1), np.nan, timedelta(2)]),
@@ -198,7 +200,7 @@ def test_api_per_dtype(self, box, dtype, all_skipna_inferred_dtypes):
         if dtype == 'category' and inferred_dtype in ['period', 'interval']:
             pytest.xfail(reason='Conversion to numpy array fails because '
                          'the ._values-attribute is not a numpy array for '
-                         'PeriodIndex/IntervalIndex; see GH 23553')
+                         'PeriodArray/IntervalArray; see GH 23553')
 
         types_passing_constructor = ['string', 'unicode', 'empty',
                                      'bytes', 'mixed', 'mixed-integer']
@@ -237,23 +239,26 @@ def test_api_per_method(self, box, dtype,
                 and inferred_dtype != 'bytes'):
             pytest.xfail(reason='Method not nan-safe on Index; see GH 23558')
         if (method_name == 'get_dummies' and box == Index
-                and inferred_dtype == 'empty' and dtype == object):
-            pytest.xfail(reason='Need to fortify get_dummies corner case')
+                and inferred_dtype == 'empty' and (dtype == object
+                                                   or values.size == 0)):
+            pytest.xfail(reason='Need to fortify get_dummies corner cases')
 
         t = box(values, dtype=dtype)  # explicit dtype to avoid casting
         method = getattr(t.str, method_name)
 
         bytes_allowed = method_name in ['encode', 'decode', 'len']
         # as of v0.23.4, all methods except 'cat' are very lenient with the
         # allowed data types, just returning NaN for entries that error.
-        # This could be changed with an 'errors'-kwarg to the `str`-accessor.
+        # This could be changed with an 'errors'-kwarg to the `str`-accessor,
+        # see discussion in GH 13877
         mixed_allowed = method_name not in ['cat']
 
         allowed_types = (['string', 'unicode', 'empty']
                          + ['bytes'] * bytes_allowed
                          + ['mixed', 'mixed-integer'] * mixed_allowed)
 
         if inferred_dtype in allowed_types:
+            # i.a. GH 23555, GH 23556
             method(*minimal_args)  # works!
         else:
             # GH 23011, GH 23163