keirsalterego opened a new pull request, #9141:
URL: https://github.com/apache/arrow-rs/pull/9141

   …Array
   
   # Which issue does this PR close?
   
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   - Closes #6528.
   
   # Rationale for this change
   
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   I kept running into situations where I needed to update the null buffer of 
an array, usually to apply a filter or mask on top of existing nulls. Right now 
that forces you to drop down to unsafe APIs to rebuild the array from raw 
parts, which isn't ideal for such a common operation.
   
   I wanted a safe API that handles this without risking undefined behavior. By 
defining the operation as a union of nulls (intersecting validity), we ensure 
that we only ever mark valid slots as null and never accidentally unmask 
garbage data. This makes it safe for all array types while covering the main 
use case of applying validity masks.
   
   # What changes are included in this PR?
   
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   I implemented `with_nulls` for `PrimitiveArray`, `BooleanArray`, and 
`GenericByteArray`. The implementation relies on `NullBuffer::union` to safely 
merge the new validity mask with the existing one.
   
   I also added documentation with examples for each implementation and made 
sure to document that it panics if the buffer lengths don't match.
   
   # Are these changes tested?
   
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   I verified the changes locally by running the existing tests for arrow-array.
   
   # Are there any user-facing changes?
   
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   This adds the public `with_nulls` method to the array types I mentioned 
above.
   


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