ROB: Deal with wrong size for incremental PDF files

[stefan6419846]

There are incremental PDF files in the wild which define a too small /Size in the final part.

I have initially seen this with an incremental PDF file where no object has been updated and the /Size set to 1, although the previous /Size would be 24. During analysis, it turned out that loading the same PDF file in incremental mode would not fail, but with /Size 2 (due to subtracting 1 in this path).

I could not see any negative side effects when changing this for non-incremental writer mode in pypdf, thus the assertion appears to be too strict here. Instead, replace the assertion with a proper error/warning message and report proper errors on an index error when attempting to flatten the faulty PDF in incremental mode.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 97.09%. Comparing base (54c0dd7) to head (b72444a).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@ Coverage Diff @@ ## main #3495 +/- ## ======================================= Coverage 97.09% 97.09% ======================================= Files 56 56 Lines 9658 9664 +6 Branches 1748 1750 +2 ======================================= + Hits 9377 9383 +6  Misses 168 168 Partials 113 113 

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.