[GitHub] [arrow] 0x26res opened a new issue, #15109: Can't create a non empty StructArray with no field using `StructArray.from_array`

[GitBox]

0x26res opened a new issue, #15109:
URL: https://github.com/apache/arrow/issues/15109

   ### Describe the bug, including details regarding any error messages, 
version, and platform.
   
   I want to create a StructArray with several rows but no fields/columns:
   
   ```
       array = pa.StructArray.from_arrays(arrays=[], names=[], 
mask=pa.array([True, True]))
       assert array.type == pa.struct([])
       assert len(array) == 0 # This is wrong
   ```
   
   As commented in the code `len(array)` is wrong and should be 2 (according to 
the provided mask).
   
   I found a work around but it's not ideal:
   
   ```
       array = pa.StructArray.from_arrays(
           arrays=[pa.nulls(2, pa.null())], names=["DELETE"], 
mask=pa.array([True, True])
       )
       assert len(array) == 2
       empty_array = array.cast(pa.struct([]))
       assert len(empty_array) == 2
       assert empty_array.type == pa.struct([])
   ```
   
   
   
   ### Component(s)
   
   Python


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