Function test_dataset_null_to_dictionary_cast

python/pyarrow/tests/test_dataset.py:5227–5242

(tempdir, dataset_reader)

@pytest.mark.parquet
def test_dataset_null_to_dictionary_cast(tempdir, dataset_reader):
    # ARROW-12420
    table = pa.table({"a": [None, None]})
    pq.write_table(table, tempdir / "test.parquet")

    schema = pa.schema([
        pa.field("a", pa.dictionary(pa.int32(), pa.string()))
    ])
    fsds = ds.FileSystemDataset.from_paths(
        paths=[tempdir / "test.parquet"],
        schema=schema,
        format=ds.ParquetFileFormat(),
        filesystem=fs.LocalFileSystem(),
    )
    table = dataset_reader.to_table(fsds)
    assert table.schema == schema


@pytest.mark.dataset