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BUG: resolve UnboundLocalError for xobjs in _get_image#3684

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stefan6419846 merged 6 commits intopy-pdf:mainfrom
Yuki9814:fix/xobjs-unbound-in-get-image
Mar 17, 2026
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BUG: resolve UnboundLocalError for xobjs in _get_image#3684
stefan6419846 merged 6 commits intopy-pdf:mainfrom
Yuki9814:fix/xobjs-unbound-in-get-image

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@Yuki9814 Yuki9814 commented Mar 15, 2026

Description

Fixes a potential UnboundLocalError in the _get_image() method of pypdf/_page.py.

The Bug

In pypdf/_page.py, the _get_image() method uses a try-except block to retrieve XObject resources:

try:
    xobjs = cast(
        DictionaryObject, cast(DictionaryObject, obj[PG.RESOURCES])[RES.XOBJECT]
    )
except KeyError:
    if not (id[0] == "~" and id[-1] == "~"):
        raise
# Later...
imgd = _xobj_to_image(cast(DictionaryObject, xobjs[id]))  # BUG: xobjs may be unbound!

If a KeyError is raised (no XObject resources) but the id starts and ends with ~ (indicating an inline image), the exception is silently caught and the code continues. However, for non-inline images, the subsequent code tries to access xobjs, which was never assigned, causing UnboundLocalError: local variable 'xobjs' referenced before assignment.

The Fix

Initialize xobjs = None before the try block and add explicit checks before using it:

xobjs: Optional[DictionaryObject] = None
try:
    xobjs = cast(...)
except KeyError:
    if not (id[0] == "~" and id[-1] == "~"):
        raise

# Later...
if xobjs is None:
    raise KeyError(f"Cannot access image object {id} without XObject resources")
imgd = _xobj_to_image(cast(DictionaryObject, xobjs[id]))

This ensures that if xobjs is None, we raise a clear KeyError instead of crashing with an UnboundLocalError.

Testing

The fix maintains backward compatibility:

  • Inline images (id like ~0~) continue to work without XObject resources
  • Non-inline images properly raise KeyError if XObject resources are missing

@Yuki9814
fix: resolve UnboundLocalError for xobjs in _get_image method
8f738f3 
The xobjs variable was used outside the try-except block that defined it.
If a KeyError was caught and the id started/ended with '~' (inline images),
the code would continue but xobjs would remain undefined, causing
UnboundLocalError when trying to access non-inline images.

Initialize xobjs to None and check before using it.
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codecov bot commented Mar 15, 2026 •
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Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 97.42%. Comparing base (8f1f4aa) to head (3fc27dd).
⚠️ Report is 5 commits behind head on main.

Additional details and impacted files 
@@            Coverage Diff             @@
##             main    #3684      +/-   ##
==========================================
+ Coverage   97.41%   97.42%   +0.01%     
==========================================
  Files          55       55              
  Lines        9989     9990       +1     
  Branches     1833     1835       +2     
==========================================
+ Hits         9731     9733       +2     
+ Misses        150      149       -1     
  Partials      108      108

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@Yuki9814 Yuki9814 changed the title fix: Resolve UnboundLocalError for xobjs in _get_image method BUG: resolve UnboundLocalError for xobjs in _get_image Mar 15, 2026
stefan6419846
stefan6419846 requested changes Mar 15, 2026
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Thanks for the report. Please revert all unrelated changes and add a corresponding test to allow me to continue with the review.

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Yuki9814 commented Mar 15, 2026

Reverted the unrelated formatting changes and kept the _get_image fix minimal. I also added a regression test in ests/test_images.py covering inline image access when /XObject resources are missing.

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Yuki9814 commented Mar 16, 2026

All requested changes should now be addressed: the unrelated formatting changes were reverted, a regression test was added, and the full CI is now green. If you have time, I'd appreciate another look.

stefan6419846
stefan6419846 requested changes Mar 16, 2026
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Yuki9814 commented Mar 16, 2026

Addressed the latest review notes: I removed the new # pragma: no cover markers from the _get_image change and simplified the regression test to use object() instead of mock.sentinel. I also reran python -m pytest tests/test_images.py -k "inline_image_without_xobject_resources" -q locally, and it passed.

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stefan6419846 commented Mar 16, 2026

Could you please add tests for the error cases as well?

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Yuki9814 commented Mar 17, 2026

Added the requested error-case coverage as well:

  • inline image lookup now has a test for the missing-inline-images path
  • regular XObject lookup now has a test for missing /XObject resources

I also tightened the _get_image error handling so the non-inline path now raises the intended KeyError message instead of leaking the raw missing-dictionary key, and reran the targeted tests plus ruff locally.

stefan6419846
stefan6419846 approved these changes Mar 17, 2026
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Thanks.

@stefan6419846 stefan6419846 merged commit 04b0a38 into py-pdf:main Mar 17, 2026
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stefan6419846 added a commit that referenced this pull request Mar 23, 2026
@stefan6419846
REL: 6.9.2
da867f4 
## What's new

### Security (SEC)
- Avoid infinite loop in read_from_stream for broken files (#3693) by @stefan6419846

### Robustness (ROB)
- Resolve UnboundLocalError for xobjs in _get_image (#3684) by @Yuki9814

[Full Changelog](6.9.1...6.9.2)
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