BUG: Fix handling of radio buttons

pypdf/_writer.py

@@ -1027,7 +1027,7 @@ def update_page_form_field_values(
                     appearance_stream_obj = normal_ap.get(v)
                     # Other cases will be updated through the for loop
                     annotation[NameObject(AA.AS)] = v
-                    annotation[NameObject(FA.V)] = v
+                    parent_annotation[NameObject(FA.V)] = v
                 elif (
                     parent_annotation.get(FA.FT) == "/Tx"
                     or parent_annotation.get(FA.FT) == "/Ch"

tests/test_forms.py

@@ -5,6 +5,7 @@
 import pytest
 
 from pypdf import PdfReader, PdfWriter
+from pypdf.generic import NameObject
 from tests import get_data_from_url
 
 
@@ -24,3 +25,46 @@ def test_form_button__v_value_should_be_name_object():
 
     # Wrong: `/V (/On)`.
     assert b"\n/V /On\n" in stream.getvalue()
+
+
+@pytest.mark.enable_socket
+def test_radio_button_handling():
+    url = "https://github.com/user-attachments/files/23957527/TemplateReproBug.pdf"
+    name = "issue3549.pdf"
+    writer = PdfWriter(clone_from=BytesIO(get_data_from_url(url, name=name)))
+    writer.update_page_form_field_values(
+        writer.pages[0],
+        {"Radio Button 3": "/1"},
+    )
+
+    radio_button3 = writer.get_fields()["Radio Button 3"]
+    assert radio_button3 == {
+        "/T": "Radio Button 3",
+        "/FT": "/Btn",
+        "/TU": "Reason for Enrollment",
+        "/Ff": 49152,
+        "/V": "/1",
+        "/Kids": [writer.get_object(17).indirect_reference, writer.get_object(52).indirect_reference],
+        "/Opt": ["New", "Add Dependant"],
+        "/_States_": ["/0", "/1"]
+    }
+    assert isinstance(radio_button3["/V"], NameObject), type(radio_button3["/V"])
+
+    writer.update_page_form_field_values(
+        writer.pages[0],
+        {"Radio Button 3": "/0"},
+    )
+    radio_button3 = writer.get_fields()["Radio Button 3"]
+    assert radio_button3 == {
+        "/T": "Radio Button 3",
+        "/FT": "/Btn",
+        "/TU": "Reason for Enrollment",
+        "/Ff": 49152,
+        # TODO: Should be `/0`. Issue: https://github.com/py-pdf/pypdf/issues/3549
+        #       Then we might want to use a parametrized function instead of repeating everything.
+        "/V": "/Off",
+        "/Kids": [writer.get_object(17).indirect_reference, writer.get_object(52).indirect_reference],
+        "/Opt": ["New", "Add Dependant"],
+        "/_States_": ["/0", "/1"]
+    }
+    assert isinstance(radio_button3["/V"], NameObject), type(radio_button3["/V"])