Fix IndexError on empty single-count field values (#254) - #256
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When a non-ASCII field is declared with count 1 but decoding produced no value (e.g. a float field whose data is truncated/corrupted, which _process_field skips with a 'Possibly corrupted field' warning), _get_printable_for_field did str(values[0]) on an empty list and raised IndexError, aborting the whole process_file call. Guard the index and fall back to an empty string, matching the conservative behavior of the ASCII path. Adds a synthetic 26-byte TIFF fixture reproducing the empty-value path and a regression test.
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Fixes #254.
Problem
process_filecrashes withIndexError: list index out of rangeatexif_header.py:241. When a non-ASCII field is declared withcount == 1but decoding produced no value — e.g. a float field whose data is truncated/corrupted, which_process_fielddeliberately skips with aPossibly corrupted fieldwarning —valuesis left empty whilecountis still1._get_printable_for_fieldthen doesstr(values[0])on the empty list and raises, aborting the whole read (this is the path hit by some DJI MakerNote blocks, per the issue).Fix
Guard the index: use
str(values[0]) if values else "", matching the conservative empty-string behavior already used on the ASCII path. This is the fix suggested in the issue.Test
@ianare asked for a sample to regress against. Rather than a proprietary DJI image, I added a synthetic 26-byte little-endian TIFF fixture (
tests/resources/tiff/empty_float_value.tiff) with one FLOAT64count=1entry whose value pointer is past EOF, which reproduces the empty-valuespath exactly. The test reads it and assertsprintable == "". Without the fix it raises theIndexErrorfrom the issue; with it the full suite passes (32).Disclosure: I used AI assistance (Claude) to help locate and draft this fix, under my direction and review.