[Python] Slicing array can lead to negative length

[asfimport]

Slice an arrow array can lead to a negative length, when instead it should never be smaller than 0.

arr = pa.array(range(10))
assert len(arr[-9:-20]) == 0

Array.length() returns -1 which makes the previous snippet crash as Python never accepts length < 0

In particular if you have Python in debug mode it will explicitly fail the related assertion
Assertion failed: (len >= 0 || PyErr_Occurred()), function PyObject_Size, file Objects/abstract.c, line 61

Reporter: Alessandro Molina / @amol-
Assignee: Alessandro Molina / @amol-

Related issues:

• [Python] Negative out of range slices yield invalid arrays (is a clone of)

_{Note: This issue was originally created as ARROW-12893. Please see the migration documentation for further details.}

[asfimport]

Joris Van den Bossche / @jorisvandenbossche:
This seems similar to something I recently fixed in #10341 / ARROW-12769, and your snippet runs correctly on master for me?

[asfimport]

Alessandro Molina / @amol-:
Can confirm that now the cases that I found work correctly, will mark as already fixed