MutaFix run: more-itertools-010

tests/test_more.py::ClassifyUniqueTests::test_vs_unique_justseen_key
tests/test_recipes.py::UniqueJustseenTests::test_custom_key

E   AssertionError: Lists differ: ['A', 'B', 'C', 'c', 'A', 'D'] != ['A', 'B', 'C', 'A', 'D']
E   
E   First differing element 3:
E   'c'
E   'A'
E   
E   First list contains 1 additional elements.
E   First extra element 5:
E   'D'
E   
E   - ['A', 'B', 'C', 'c', 'A', 'D']
E   ?                 -----
E   
E   + ['A', 'B', 'C', 'A', 'D']

E   AssertionError: Lists differ: ['A', 'B', 'C', 'A', 'D'] != ['A', 'B', 'C', 'c', 'A', 'D']
E   
E   First differing element 3:
E   'A'
E   'c'
E   
E   Second list contains 1 additional elements.
E   First extra element 5:
E   'D'
E   
E   - ['A', 'B', 'C', 'A', 'D']
E   + ['A', 'B', 'C', 'c', 'A', 'D']
E   ?                 +++++

1. more_itertools/recipes.py::unique_justseen call depth 1 · Ochiai 0.50 (failing 2, passing 6)
2. more_itertools/more.py::classify_unique call depth 1 · Ochiai 0.19 (failing 1, passing 13)
3. more_itertools/recipes.py::unique_everseen call depth - · Ochiai 0.00 (failing 0, passing 10)
4. more_itertools/more.py::duplicates_justseen call depth - · Ochiai 0.00 (failing 0, passing 9)
5. more_itertools/more.py::all_unique call depth - · Ochiai 0.00 (failing 0, passing 5)
6. more_itertools/more.py::duplicates_everseen call depth - · Ochiai 0.00 (failing 0, passing 8)
7. more_itertools/recipes.py::unique call depth - · Ochiai 0.00 (failing 0, passing 3)
8. more_itertools/recipes.py::all_equal call depth - · Ochiai 0.00 (failing 0, passing 19)
9. more_itertools/more.py::unique_to_each call depth - · Ochiai 0.00 (failing 0, passing 3)
10. more_itertools/more.py::unique_in_window call depth - · Ochiai 0.00 (failing 0, passing 3)
11. more_itertools/more.py::is_sorted call depth - · Ochiai 0.00 (failing 0, passing 1)
12. more_itertools/more.py::distinct_combinations call depth - · Ochiai 0.00 (failing 0, passing 3)
13. more_itertools/more.py::minmax call depth - · Ochiai 0.00 (failing 0, passing 6)
14. more_itertools/more.py::sort_together call depth - · Ochiai 0.00 (failing 0, passing 6)
15. more_itertools/more.py::groupby_transform call depth - · Ochiai 0.00 (failing 0, passing 5)
16. more_itertools/more.py::takewhile_inclusive call depth - · Ochiai 0.00 (failing 0, passing 3)
17. more_itertools/more.py::distinct_permutations call depth - · Ochiai 0.00 (failing 0, passing 8)
18. more_itertools/more.py::unzip call depth - · Ochiai 0.00 (failing 0, passing 5)
19. more_itertools/more.py::_sample_weighted call depth - · Ochiai 0.00 (failing 0, passing 5)
20. more_itertools/more.py::make_decorator call depth - · Ochiai 0.00 (failing 0, passing 3)

We need to understand what's happening. The error says "'tuple' object is not an iterator". That suggests we tried to call next on something that is not an iterator? Actually our new code:

return map(lambda x: next(x), groupby(iterable, key))

But note: groupby returns an iterator of tuples (key, group_iterator). So x is a tuple (k, g). Then we do next(x) -> trying to get the first item of the tuple? No, next(x) tries to iterate over the tuple as an iterator, yielding its items. But we want the first element of the group, not the key. Actually we want the first element of the group iterator g. In standard recipes, unique_justseen with key is implemented as:

def unique_justseen(iterable, key=None):
    return map(next, map(itemgetter(1), groupby(iterable, key)))

Wait look at the original code: there were two branches. When key is None, they did: return map(next, map(itemgetter(1), groupby(iterable, key))) ??? Let's re-examine original:

Original lines 520-523:

    if not (key is None):
        return map(itemgetter(0), groupby(iterable))

    return map(next, map(itemgetter(1), groupby(iterable, key)))

So when key is None, they do: groupby(iterable) -> returns (key, group) where key is the element itself (since no key function). Then map(itemgetter(1)) gets the group iterator, then map(next) gets the first element of each group. That yields the original elements.

When key is not None, they incorrectly did: map(itemgetter(0), groupby(iterable)) -> they forgot to use the k