Preserve falsy values (0, False) in jira and latex exports

[koriyoshi2041]

The JIRA and LaTeX serializers decide whether a cell is empty with a plain truthiness test:

# _jira.py
delimiter.join([str(item) if item else " " for item in row])
# _latex.py
new_row = [cls._escape_tex_reserved_symbols(str(item)) if item else "" for item in row]

So 0, 0.0, and False — all valid data — are treated as missing and exported as blank cells, silently losing data. For example tablib.Dataset([0, False, "c"]).jira produced | | |c| instead of |0|False|c|.

The HTML format already does this correctly with str(item) if item is not None else "", so "blank only for missing values" is the intended contract. This changes both serializers to test item not in (None, ""), which keeps the existing None/empty-string behaviour (still rendered blank) while preserving real falsy values.

Added test_jira_export_falsy_values and test_latex_export_falsy_values; the existing *_none_* tests still pass. pytest -k "jira or latex" is green (12 passed).

[hugovk]

This also changes the display of other falsy things.

With this script:

import tablib

# The fix itself: 0 and False are real values.
print(repr(tablib.Dataset([0, False, 'c']).jira))

# Finding 1: change is broader than 0/False — falsy containers/bytes now
# render their reprs instead of blank cells (jira and latex alike).
print(repr(tablib.Dataset([[], {}, 'c']).jira))

# Finding 2: b'' hits a bytes-vs-str comparison in `item not in (None, '')`
# — raises BytesWarning under -bb (master rendered a blank cell).
print(repr(tablib.Dataset([b'', 'c']).jira))

main:

'| | |c|'
'| | |c|'
'| |c|'

PR:

'|0|False|c|'
'|[]|{}|c|'
"|b''|c|"

And if we run with bytes warnings: python -b repro.py:

main:

'| | |c|'
'| | |c|'
'| |c|'

PR:

'|0|False|c|'
'|[]|{}|c|'
/Users/hugo/github/tablib/src/tablib/formats/_jira.py:38: BytesWarning: Comparison between bytes and string
  delimiter.join([str(item) if item not in (None, '') else ' ' for item in row]),
/Users/hugo/github/tablib/src/tablib/formats/_jira.py:38: BytesWarning: str() on a bytes instance
  delimiter.join([str(item) if item not in (None, '') else ' ' for item in row]),
"|b''|c|"

[hugovk]

We can simplify this:

Suggested change

	new_row = [cls._escape_tex_reserved_symbols(str(item)) if item not in (None, '') else ''
	new_row = ['' if item is None else cls._escape_tex_reserved_symbols(str(item))

[hugovk]

Suggested change

	delimiter.join([str(item) if item not in (None, '') else ' ' for item in row]),
	delimiter.join([' ' if item in (None, '') else str(item) for item in row]),

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 93.28%. Comparing base (7503651) to head (2db3ddc).
⚠️ Report is 5 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #643      +/-   ##
==========================================
+ Coverage   93.14%   93.28%   +0.13%     
==========================================
  Files          29       29              
  Lines        3226     3293      +67     
==========================================
+ Hits         3005     3072      +67     
  Misses        221      221              

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[hugovk]

Move this to utils.py and deduplicate.

[hugovk]

This could be a single:

if isinstance(item, (str, bytes, bytearray, list, tuple, dict, set, frozenset)) and len(item) == 0:
    return True

[hugovk]

cls is never used, can remove @classmethod and cls at the call site.