Fix TypeError: can only join an iterable with AECCAR in VolumetricData.write_file

[chiang-yuan]

Context: I was trying to download AECCARs from aws and save them locally as vasp compatible format. CHGCARs can pass successfully but AECCAR will yield error when aeccar.write_file like following

mp_id = 'mp-1523380'
prefix = 'aeccar0s'
suffix = prefix.rstrip("s")

fpath = f'{mp_id}-{suffix}.json.gz'

with zopen(fpath) as f:
    json_string = f.read()
    data = json.loads(json_string, cls=MontyDecoder)['data']
    data.write_file(f'{mp_id}.{suffix.upper()}')

Modify io/vasp/outputs.py to do the Iterable check first and only write to file when self.data_aug.get(data_type, []) is not empty

Checklist

• ruff
• mypy
• pre-commit

[chiang-yuan]

tag @tschaume you might be interested to comment since I mentioned this bug to you 😄

[janosh]

Thanks @chiang-yuan! Could you mention the error type and message you're seeing? We'll also need a test for this. You can maybe use tests/files/bader/AECCAR0.gz

[chiang-yuan]

The error I received is

-> 3585 f.write("".join(self.data_aug.get(data_type, [])))

TypeError: can only join an iterable

@janosh this is a file output bug, so do you want me to check if the file looks identical to itself after read in and output?

[janosh]

@janosh this is a file output bug, so do you want me to check if the file looks identical to itself after read in and output?

Sounds good! Just writing to disk would be enough to test this fix but checking for equality after re-read is even better.

[chiang-yuan]

Test added :) @janosh

[janosh]

Why is it ok here not to write to file if data is not Iterable?

[chiang-yuan]

If data_aug is empty and not Iterable, join will give the error.

[janosh]

But do we want to write an empty file in that case? Having no file after calling write_file sounds like unexpected behavior.

[chiang-yuan]

Only the partial of the file (data_aug) will not be written if it is empty. The rest of the file will still be there.

[janosh]

This needs to be asserted. Just calling np.allclose doesn't fail the test if the check fails.

[chiang-yuan]

Oh!!! Thanks for the good catch. I missed that.

[chiang-yuan]

Thanks for the help @janosh! All look good to me 😃

[janosh]

Thanks for the test! 👍