Collapsing outlines not working: parameter is_open in add_outline_item has no effect

[dowo-2987]

I tried adding a (nested) outline to a document, and I wanted it to be collapsed by default when opening the file. So I set is_open to False in writer.add_outline_item, but the outlines are still all expanded.

I looked a bit into the code, and from my understanding the problem lies in writer.add_outline_destination when calling parent.insert_child:
When giving the inc_parent_counter, a default inc_parent_counter_outline is passed if is_open == True, and some lambda returning 0 at all times otherwise. However it seems to be exactly the inc_parent_counter_outline that handles setting "/Count" to -1 if the outlines should be collapsed. So I removed the if statement (so it always passes inc_parent_counter_outline), and now my outlines are collapsed. So this seems to fix it, however I have no idea whether that breaks anything else that doesn't affect my usecase.

In case it helps:
Change

parent.insert_child(
            page_destination_ref,
            before,
            self,
            page_destination.inc_parent_counter_outline
            if is_open
            else (lambda x, y: 0),
        )

to

parent.insert_child(
            page_destination_ref,
            before,
            self,
            page_destination.inc_parent_counter_outline,
        )

Environment

python 3.10.12 in WSL

$ python3 -m platform
# Linux-5.15.167.4-microsoft-standard-WSL2-x86_64-with-glibc2.35

$ python3 -c "import pypdf;print(pypdf._debug_versions)"
# pypdf==5.1.0, crypt_provider=('cryptography', '43.0.3'), PIL=10.3.0

Code + PDF

This is a minimal (I hope), complete example that shows the issue:

import pypdf

pdf_in = "test.pdf"
pdf_out = "output.pdf"
reader = pypdf.PdfReader(pdf_in)
writer = pypdf.PdfWriter()

# Copy the pdf
for page in reader.pages:
    writer.add_page(page)

# Create outline
parent = writer.add_outline_item("Parent Item", 0, is_open=False)
writer.add_outline_item("Child Item", 0, parent=parent, is_open=False)

# Write the new file
with open(pdf_out, "wb") as f:
        writer.write(f)

Any PDF should produce this issue, however I append a random minimal pdf that does produce the issue: test.pdf

Traceback

There is no traceback.