waterWang opened a new pull request, #24343:
URL: https://github.com/apache/datafusion/pull/24343
## Which issue does this PR close?
Closes #24341.
## What changes are included in this PR?
`general_array_slice` in `extract.rs` was rebuilding the output list's inner
field from scratch using `Field::new_list_field(array.value_type(), true)`,
which always produces `Field("item", T, nullable: true)`. This discards the
input field's name, nullability, and metadata, contradicting
`ArraySlice::return_type` which promises `arg_types[0].clone()`.
This fix extracts the field from the input array's data type instead,
matching the approach already used in `general_list_view_array_slice` for
ListView arrays.
## Are these changes tested?
Yes. Added `test_array_slice_preserves_inner_field` which verifies that the
output list type preserves the input field's name and nullability.
## Issue body for reference
### Describe the bug
`ArraySlice::return_type` promises `arg_types[0].clone()`, i.e. the input
list type verbatim — inner field name, nullability and metadata included. But
the kernel rebuilds the output's inner field from scratch in
`general_array_slice`
([`extract.rs:685`](https://github.com/apache/datafusion/blob/main/datafusion/functions-nested/src/extract.rs#L685)):
```rust
Ok(Arc::new(GenericListArray::<O>::try_new(
Arc::new(Field::new_list_field(array.value_type(), true)),
...
```
That drops the field name (any name → `item`), drops inner metadata, and
forces `nullable: true`. Whenever the input list's inner field is anything
other than `Field("item", T, nullable: true)`, the returned array disagrees
with the promised type. On debug builds this trips the return-type assertion
added in #17515; on release builds it silently produces a batch whose field
name/nullability disagrees with the schema the planner recorded.
This is the same defect fixed for `array_sort` in #19
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