BUG: Add the TK.SIZE into the trailer

[talcher]

Closes #1901

[codecov]

Codecov Report

Patch coverage: 100.00% and project coverage change: -1.01 ⚠️

Comparison is base (cd4c9d8) 93.83% compared to head (adde37b) 92.83%.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1911      +/-   ##
==========================================
- Coverage   93.83%   92.83%   -1.01%     
==========================================
  Files          34       34              
  Lines        6943     7058     +115     
  Branches     1370     1389      +19     
==========================================
+ Hits         6515     6552      +37     
- Misses        282      359      +77     
- Partials      146      147       +1     

Impacted Files	Coverage Δ
pypdf/_reader.py	91.33% <100.00%> (ø)

... and 5 files with indirect coverage changes

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[MartinThoma]

Looks fine to me.

From "Table 15 – Entries in the file trailer dictionary" of the 1.7 specs:

(Required; shall not be an indirect reference) The total number of entries in
the file’s cross-reference table, as defined by the combination of the original
section and all update sections. Equivalently, this value shall be 1 greater
than the highest object number defined in the file.

Any object in a cross-reference section whose number is greater than this
value shall be ignored and defined to be missing by a conforming reader.

I wonder why this wasn't observed earlier.

@pubpub-zz What do you think?

[pubpub-zz]

Mod looks good. Can you just a check that the /Size is present:
I propose just to add at the end of one test to confirm Size will not disappear (picked up randomly 😉):

@pytest.mark.enable_socket()
    def test_append_forms():
    # from #1538
    writer = PdfWriter()

    url = "https://github.com/py-pdf/pypdf/files/10367412/pdfa.pdf"
    name = "form_a.pdf"
    reader1 = PdfReader(BytesIO(get_pdf_from_url(url, name=name)))
    reader1.add_form_topname("form_a")
    writer.append(reader1)

    url = "https://github.com/py-pdf/pypdf/files/10367413/pdfb.pdf"
    name = "form_b.pdf"
    reader2 = PdfReader(BytesIO(get_pdf_from_url(url, name=name)))
    reader2.add_form_topname("form_b")
    writer.append(reader2)

    b = BytesIO()
    writer.write(b)
    reader = PdfReader(b)
    assert len(reader.get_form_text_fields()) == len(
        reader1.get_form_text_fields()
    ) + len(reader2.get_form_text_fields())
   assert "/Size" in reader.trailer                          # <----  added

[talcher]

The check is added. I hope the test I chose is OK for you.
The problem is: a codecov check is unsuccessful and the PR does not have a green tick anymore, but a red cross.
Any idea to correct that?

[MartinThoma]

Thank you for the contribution! The fix is now in main. A new version of pypdf will be on PyPI latest on Sunday (2nd of June, 2023)

[MartinThoma]

If you want, I can add you to https://pypdf.readthedocs.io/en/latest/meta/CONTRIBUTORS.html :-)