dualfroz
9194f6d3ad
sorted_last_index returns 0 for an empty array (and for any value smaller than every element), so index becomes -1. The guard only bounded index from above, so array[-1] was evaluated on an empty list and raised IndexError. Add the lower-bound check so a negative index is reported as not found, matching sorted_index_of.
75 lines
2.1 KiB
Markdown
75 lines
2.1 KiB
Markdown
# Fix `sorted_last_index_of` raising IndexError on empty array
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## Problem
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`pydash.sorted_last_index_of(array, value)` raises `IndexError` when `array` is
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empty, instead of returning `-1` (the documented "not found" result):
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```python
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>>> import pydash
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>>> pydash.sorted_last_index_of([], 10)
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Traceback (most recent call last):
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...
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IndexError: list index out of range
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```
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The sibling function `sorted_index_of` returns `-1` for the same input, so the
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two are inconsistent.
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## Root cause
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`src/pydash/arrays.py`, in `sorted_last_index_of`:
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```python
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index = sorted_last_index(array, value) - 1
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if index < len(array) and array[index] == value:
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return index
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else:
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return -1
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```
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`sorted_last_index` returns `0` for an empty array (and whenever `value` is
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smaller than every element), so `index` becomes `-1`. The guard only checks the
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upper bound (`index < len(array)`); since `-1 < 0` is `True` for an empty array,
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`array[index]` is evaluated as `array[-1]` on an empty list, raising
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`IndexError`. For a non-empty array the same `index == -1` accidentally avoids a
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wrong result only because `array[-1]` happens not to equal a value smaller than
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`array[0]`; the missing lower-bound check is still a latent correctness issue.
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## Fix
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Add the lower-bound check so a negative computed index is treated as
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"not found":
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```python
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if 0 <= index < len(array) and array[index] == value:
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return index
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else:
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return -1
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```
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## Test
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Extended `test_sorted_last_index_of` in `tests/test_arrays.py` with the
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empty-array case and a value-below-range case:
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```python
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([], 10, -1),
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([2, 3, 4], 1, -1),
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```
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## Gate
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- `python -m pytest tests/test_arrays.py -k test_sorted_last_index_of` -> 4 passed
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- `python -m pytest tests/ --ignore=tests/pytest_mypy_testing` -> 1917 passed
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Counterfactual (fix reverted, test kept): the empty-array case fails with
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`IndexError: list index out of range` at `arrays.py` in `sorted_last_index_of`.
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## Flags for the account owner
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The `tests/pytest_mypy_testing/` suite fails locally with `NameError` (the
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`reveal_type` typing plugin is not resolvable in a bare `pip install -e .`
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environment). These failures are pre-existing and unrelated to this change.
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