BUG: Fix merge_page sometimes generating unknown operator 'QQ' (#2588)

Fixes #2587

Author: rfotino

pypdf/generic/_data_structures.py

@@ -1256,7 +1256,7 @@ def isolate_graphics_state(self) -> None:
             self._operations.insert(0, ([], "q"))
             self._operations.append(([], "Q"))
         elif self._data:
-            self._data = b"q\n" + b_(self._data) + b"Q\n"
+            self._data = b"q\n" + b_(self._data) + b"\nQ\n"
 
     # This overrides the parent method:
     def write_to_stream(

tests/test_page.py

@@ -1268,6 +1268,19 @@ def test_pdf_pages_missing_type():
     writer.pages[0]
 
 
+@pytest.mark.enable_socket()
+def test_merge_with_stream_wrapped_in_save_restore():
+    """Test for issue #2587"""
+    url = "https://github.com/py-pdf/pypdf/files/14895914/blank_portrait.pdf"
+    name = "blank_portrait.pdf"
+    reader = PdfReader(BytesIO(get_data_from_url(url, name=name)))
+    page_one = reader.pages[0]
+    assert page_one.get_contents().get_data() == b"q Q"
+    page_two = reader.pages[0]
+    page_one.merge_page(page_two)
+    assert b"QQ" not in page_one.get_contents().get_data()
+
+
 @pytest.mark.samples()
 def test_compression():
     """Test for issue #1897"""