Cyclic Widget /Parent makes page operations fail with FzErrorFormat: code=7: cycle in resources

Description of the bug

PyMuPDF raises pymupdf.mupdf.FzErrorFormat: code=7: cycle in resources when it loads or processes a page containing a Widget annotation whose /Parent entry points to itself. The malformed form-field relationship makes the complete page unusable, including operations unrelated to forms.

This seems to be distinct from #4986: the page tree is valid here. The cycle is contained in the annotation/form field graph.

Concretely, for the attached reproducer:

• Page 0 lives at xref 4 and correctly declares /Parent 2 0 R, a /Pages node.
• Page 0 declares /Annots [7 0 R 8 0 R].
• Widget 7 declares /Parent 7 0 R, i.e. itself.

7 0 obj
<<
  /Type /Annot
  /Subtype /Widget
  /P 4 0 R
  /Parent 7 0 R
  ...
>>
endobj

The error fires immediately when the page is loaded.

Besides, it also occurs through Document._do_links(): insert_pdf(..., annots=False, widgets=False, links=False) can rebuild the page, but links=True fails even with annots=False and widgets=False.

The source has no actual links. The link-copy pass still loads every source page to ask for its links, which triggers the cyclic Widget-parent traversal.

How to reproduce the bug

import pymupdf

source = pymupdf.open("repro_widget_parent_cycle.pdf")

print(f"Pages: {source.page_count}")
source.load_page(0)  # raises FzErrorFormat: code=7: cycle in resources

The same failure occurs during link copying:

destination = pymupdf.open()
destination.insert_pdf(
    source,
    annots=False,
    widgets=False,
    links=True,
)
# raises FzErrorFormat: code=7: cycle in resources

repro_widget_parent_cycle.pdf is a synthetic, one-page reproducer derived from the original PDF.

PyMuPDF version

1.28.2

Operating system

Linux

Python version

3.13