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ROB: Handle /Pages node without /Kids during flattening #3825

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ROB: Handle /Pages node without /Kids during flattening #3825

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10 changes: 9 additions & 1 deletion pypdf/_doc_common.py
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Original file line number Diff line number Diff line change
Expand Up @@ -1184,7 +1184,15 @@ def _flatten(
if attr in pages:
inherit[attr] = pages[attr]
pages_reference = getattr(pages, "indirect_reference", object())
for page in cast(ArrayObject, pages[PagesAttributes.KIDS]):
# A malformed /Pages node may be missing /Kids (for example a page
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@stefan6419846 stefan6419846 Jun 2, 2026

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I do not think that this comment contributes enough to be useful here.

# tree advertising "/Count 0" without any children). Treat it as
# having no kids instead of raising a bare KeyError here (#3811).
kids = (
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@stefan6419846 stefan6419846 Jun 2, 2026

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This can be written in a simpler way:

Suggested change
kids = (
kids = pages.get(PagesAttributes.KIDS, ArrayObject())

pages[PagesAttributes.KIDS]
if PagesAttributes.KIDS in pages
else ArrayObject()
)
for page in cast(ArrayObject, kids):
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@stefan6419846 stefan6419846 Jun 2, 2026

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While we are at it (and although not required here), I would recommend replacing this cast and increase the resilience here.

What I mean is that we should use an empty ArrayObject if the kids are a NullObject and raise a proper exception if we see anything different from an ArrayObject for the iteration.

if getattr(page, "indirect_reference", object()) == pages_reference:
raise PdfReadError("Detected cyclic page references.")

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16 changes: 16 additions & 0 deletions tests/test_doc_common.py
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Original file line number Diff line number Diff line change
Expand Up @@ -20,6 +20,7 @@
EncodedStreamObject,
NameObject,
NullObject,
NumberObject,
TextStringObject,
ViewerPreferences,
)
Expand Down Expand Up @@ -475,6 +476,21 @@ def test_flatten__cyclic_references():
reader._flatten()


def test_flatten__pages_without_kids():
# A malformed /Pages node may advertise "/Count 0" without providing any
# /Kids entry. Flattening such a page tree used to raise a bare
# ``KeyError: '/Kids'`` instead of being handled gracefully (#3811).
reader = PdfReader(RESOURCE_ROOT / "crazyones.pdf")

pages_object = reader.root_object["/Pages"]
del pages_object["/Kids"]
pages_object[NameObject("/Count")] = NumberObject(0)
reader.flattened_pages = None

assert len(reader.pages) == 0
assert list(reader.pages) == []


@pytest.mark.enable_socket
@pytest.mark.timeout(10)
def test_get_outline__cyclic_references(caplog):
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