[C++] Creating (or casting to) list array with non-nullable field doesn't check nulls

[asfimport]

When creating a ListArray where you indicate that the values field is not nullable, you can actually create the array with nulls without this is being validated:

>>> typ = pa.list_(pa.field("element", pa.int64(), nullable=False))
>>> arr = pa.array([[1, 2], [3, 4, None]], typ)
>>> arr
<pyarrow.lib.ListArray object at 0x7f75bdeba760>
[
  [
    1,
    2
  ],
  [
    3,
    4,
    null
  ]
]

>>> arr.type
ListType(list<element: int64 not null>)

Also explicitly validating it doesn't raise:

>>> arr.validate(full=True)

Is this something we should check?
What guarantees do we attach to the nullability of a field of a nested type?

Reporter: Joris Van den Bossche / @jorisvandenbossche

Related issues:

• [Python] Casting Table to new schema ignores nullability of fields (relates to)

_{Note: This issue was originally created as ARROW-15478. Please see the migration documentation for further details.}