Fix crash when traceback frame has tb_lineno=None

[Mr-Neutr0n]

Summary

• Fixes TypeError crash when formatting exceptions where a traceback frame has tb_lineno=None
• Guards against None lineno values by returning an empty source string instead of calling linecache.getline()

Details

When formatting exceptions, Loguru calls linecache.getline(filename, lineno) with the line number from traceback frames. In some edge cases on Python 3.12+, tb_lineno can be None (see CPython issues python/cpython#139531 and python/cpython#89726), which causes a TypeError:

TypeError: '<=' not supported between instances of 'int' and 'NoneType'

This happens because linecache.getline() compares lineno with integers.

Fix

The fix guards against None lineno values in the get_info() function:

if lineno is None:
    source = ""
else:
    source = linecache.getline(filename, lineno).strip()

This allows exceptions to be logged even when the source line cannot be retrieved for frames with None lineno.

Test plan

• Manually verified the fix handles None lineno gracefully
• The fix is minimal and targeted

Fixes #1435

🤖 Generated with Claude Code

[Mr-Neutr0n]

Friendly follow-up - is there anything I can improve in this PR? Happy to address any feedback. Thanks!

[Mr-Neutr0n]

Friendly bump! Let me know if there's anything I should update or improve to help move this forward.