[BUG] JSON reader fails to parse files with empty rows

[vuule]

The following test fails in both cases:

@pytest.mark.parametrize(
    "buffer",
    [
        "[ ]\n[ ]",
        '{ }\n{ }',
    ],
)
def test_json_empty(buffer):
    cu_df = cudf.read_json(buffer, lines=True)
    pd_df = pd.read_json(buffer, lines=True)

    np.testing.assert_array_equal(pd_df.dtypes, cu_df.dtypes)

With array rows, the reader creates a table with int8 column instead of an empty table.
With object rows, a CUDA error happens.

[github-actions]

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[dagardner-nv]

I can't reproduce this, however with cudf 23.02.00 I have a similar issue where cudf is failing to parse an empty json array '[]' I get an re.error exception, while an empty list with a blank space in the body '[ ]' parses regardless of the engine value:

import pandas as pd
import cudf

print(cudf.__version__)
print(pd.__version__)

try:
    cudf.read_json('[]', lines=False, engine='cudf')
except Exception as e:
    print(e)

try:
    cudf.read_json('[]', lines=False, engine='pandas')
except Exception as e:
    print(e)

# Pandas works fine
print(pd.read_json('[]', lines=False))

# Blank space works fine
print(cudf.read_json('[ ]', lines=False, engine='cudf'))
import pandas as pd
import cudf

print(cudf.__version__)
print(pd.__version__)

try:
    cudf.read_json('[]', lines=False, engine='cudf')
except Exception as e:
    print(e)

try:
    cudf.read_json('[]', lines=False, engine='pandas')
except Exception as e:
    print(e)

# Pandas works fine
print(pd.read_json('[]', lines=False))

# Blank space works fine
print(cudf.read_json('[ ]', lines=False, engine='cudf'))

output:

23.02.00
1.3.5
unterminated character set at position 31
/home/dagardner/work/conda/envs/morpheus/lib/python3.10/site-packages/cudf/io/json.py:121: UserWarning: Using CPU via Pandas to read JSON dataset, this may be GPU accelerated in the future
  warnings.warn(
unterminated character set at position 31
Empty DataFrame
Columns: []
Index: []
Empty DataFrame
Columns: []
Index: []

[GregoryKimball]

Thank you @dagardner-nv for sharing this. This is an issue we had missed in the overall JSON prioritization and it seems to impact our new nested JSON reader.

[karthikeyann]

This error does not happen in new nested JSON reader anymore.
Only difference I see is that, Index: [0, 1] in pandas, Index: [] in cudf.

Question: is it possible to have empty column with non-empty indices in cudf Dataframe?