Empty file added through .add_file() is not present in zip

[scholtalbers]

When adding a file say "empty.txt" with rocrate.add_file("empty_txt") it gets a correct entry in the metadata, but the resulting zip from write_zip() does not include that file. I would expect the file to be there.

The offending line seems to be the following, as here the file is created when a chunk is returned, which for the empty file it is not the case:

ro-crate-py/rocrate/rocrate.py

Line 497 in 9c0d8a0

for path, chunk in writeable_entity.stream(chunk_size=chunk_size):

[simleo]

@dnlbauer can you take a look at this?

[dnlbauer]

The streaming methods for data entities did not yield anything for empty files which resulted in the file being skipped by the zip writing method. My proposed solution #223 is to simply yield an empty byte if a file is empty to indicate to the writing method that there is indeed a file, but nothing to write for it.