Refactor CheckParent

Adresses issue #4004.
Calling CheckParent should raise ReferenceError, respetively ValueError if an objects parent is no longer available.

src/__init__.py

@@ -7186,6 +7186,7 @@ def _parse_da(self):
     def _validate(self):
         """Validate the class entries.
         """
+        CheckParent(self)  # ensure page still exists
         if (self.rect.is_infinite
             or self.rect.is_empty
            ):
@@ -7305,6 +7306,7 @@ def button_states(self):
 
     @property
     def next(self):
+        CheckParent(self)  # ensure page still exists
         return self._annot.next
 
     def on_state(self):
@@ -17996,9 +17998,13 @@ def CheckMorph(o: typing.Any) -> bool:
 
 
 def CheckParent(o: typing.Any):
+    try:
+        check = str(o.parent)  # will raise if no parent or weakref is dead
+        if check == "None":
+            raise ValueError(f"orphaned object: parent is None")
+    except ReferenceError, ValueError:
+        raise ValueError(f"orphaned object: parent is dead")
     return
-    if not hasattr(o, "parent") or o.parent is None:
-        raise ValueError(f"orphaned object {type(o)=}: parent is None")
 
 
 def CheckQuad(q: typing.Any) -> bool:

tests/test_parent.py

@@ -0,0 +1,16 @@
+import pymupdf
+
+
+def test_parent():
+    """Test invalidating parent on page re-assignment."""
+    doc = pymupdf.open()
+    page = doc.new_page()
+    a = page.add_highlight_annot(page.rect)  # insert annotation on page 0
+    page = doc.new_page()  # make a new page, should orphanate annotation
+    try:
+        print(a)  # should raise
+        error = False
+    except ValueError as e:
+        assert str(e) == "orphaned object: parent is dead"
+        error = True
+    assert error