fix: add notesMasterIdLst element when creating notes master

When python-pptx creates a notes master on first access to
slide.notes_slide, it correctly creates the NotesMasterPart and
adds the relationship in the .rels file, but omits the corresponding
<p:notesMasterIdLst> reference from presentation.xml. Without this
element, OOXML consumers cannot discover the notes master from the
presentation element, even though the relationship and part exist.

This causes Apple Keynote (and potentially other consumers) to
fail to recognize the notes master, breaking speaker notes import.

This fix:
- Adds CT_NotesMasterIdList and CT_NotesMasterIdListEntry element
  classes with proper ZeroOrOne/RequiredAttribute declarations
- Registers both element classes in the oxml element class lookup
- Adds a ZeroOrOne declaration for notesMasterIdLst on
  CT_Presentation with correct successor sequence
- Updates PresentationPart.notes_master_part to populate the
  notesMasterIdLst element with the relationship ID after creating
  the notes master relationship

Closes #1051

Author: robertbrodie

src/pptx/oxml/__init__.py

@@ -273,6 +273,8 @@ def register_element_cls(nsptagname: str, cls: Type[BaseOxmlElement]):
 
 
 from pptx.oxml.presentation import (  # noqa: E402
+    CT_NotesMasterIdList,
+    CT_NotesMasterIdListEntry,
     CT_Presentation,
     CT_SlideId,
     CT_SlideIdList,
@@ -281,6 +283,8 @@ def register_element_cls(nsptagname: str, cls: Type[BaseOxmlElement]):
     CT_SlideSize,
 )
 
+register_element_cls("p:notesMasterId", CT_NotesMasterIdListEntry)
+register_element_cls("p:notesMasterIdLst", CT_NotesMasterIdList)
 register_element_cls("p:presentation", CT_Presentation)
 register_element_cls("p:sldId", CT_SlideId)
 register_element_cls("p:sldIdLst", CT_SlideIdList)

src/pptx/oxml/presentation.py

@@ -17,6 +17,7 @@ class CT_Presentation(BaseOxmlElement):
     get_or_add_sldSz: Callable[[], CT_SlideSize]
     get_or_add_sldIdLst: Callable[[], CT_SlideIdList]
     get_or_add_sldMasterIdLst: Callable[[], CT_SlideMasterIdList]
+    get_or_add_notesMasterIdLst: Callable[[], CT_NotesMasterIdList]
 
     sldMasterIdLst: CT_SlideMasterIdList | None = (
         ZeroOrOne(  # pyright: ignore[reportAssignmentType]
@@ -30,6 +31,17 @@ class CT_Presentation(BaseOxmlElement):
             ),
         )
     )
+    notesMasterIdLst: CT_NotesMasterIdList | None = (
+        ZeroOrOne(  # pyright: ignore[reportAssignmentType]
+            "p:notesMasterIdLst",
+            successors=(
+                "p:handoutMasterIdLst",
+                "p:sldIdLst",
+                "p:sldSz",
+                "p:notesSz",
+            ),
+        )
+    )
     sldIdLst: CT_SlideIdList | None = ZeroOrOne(  # pyright: ignore[reportAssignmentType]
         "p:sldIdLst", successors=("p:sldSz", "p:notesSz")
     )
@@ -115,6 +127,30 @@ class CT_SlideMasterIdListEntry(BaseOxmlElement):
     rId: str = RequiredAttribute("r:id", XsdString)  # pyright: ignore[reportAssignmentType]
 
 
+class CT_NotesMasterIdList(BaseOxmlElement):
+    """`p:notesMasterIdLst` element.
+
+    Child of `p:presentation` containing a reference to the notes master that belongs to the
+    presentation.
+    """
+
+    _add_notesMasterId: Callable[..., CT_NotesMasterIdListEntry]
+    notesMasterId = ZeroOrOne("p:notesMasterId")
+
+    def add_notesMasterId(self, rId: str) -> CT_NotesMasterIdListEntry:
+        """Create and return a new `p:notesMasterId` child element with r:id set to `rId`."""
+        return self._add_notesMasterId(rId=rId)
+
+
+class CT_NotesMasterIdListEntry(BaseOxmlElement):
+    """`p:notesMasterId` element.
+
+    Child of `p:notesMasterIdLst` containing an `rId` reference to the notes master part.
+    """
+
+    rId: str = RequiredAttribute("r:id", XsdString)  # pyright: ignore[reportAssignmentType]
+
+
 class CT_SlideSize(BaseOxmlElement):
     """`p:sldSz` element.
 

src/pptx/parts/presentation.py

@@ -72,7 +72,8 @@ def notes_master_part(self) -> NotesMasterPart:
             return self.part_related_by(RT.NOTES_MASTER)
         except KeyError:
             notes_master_part = NotesMasterPart.create_default(self.package)
-            self.relate_to(notes_master_part, RT.NOTES_MASTER)
+            rId = self.relate_to(notes_master_part, RT.NOTES_MASTER)
+            self._element.get_or_add_notesMasterIdLst().add_notesMasterId(rId)
             return notes_master_part
 
     @lazyproperty

tests/parts/test_presentation.py

@@ -65,13 +65,21 @@ def but_it_adds_a_notes_master_part_when_needed(
         NotesMasterPart_ = class_mock(request, "pptx.parts.presentation.NotesMasterPart")
         NotesMasterPart_.create_default.return_value = notes_master_part_
         part_related_by_.side_effect = KeyError
-        prs_part = PresentationPart(None, None, package_, None)
+        relate_to_.return_value = "rId42"
+        prs_elm = element("p:presentation/p:sldMasterIdLst")
+        prs_part = PresentationPart(None, None, package_, prs_elm)
 
         notes_master_part = prs_part.notes_master_part
 
         NotesMasterPart_.create_default.assert_called_once_with(package_)
         relate_to_.assert_called_once_with(prs_part, notes_master_part_, RT.NOTES_MASTER)
         assert notes_master_part is notes_master_part_
+        # --- notesMasterIdLst element was added to presentation.xml ---
+        notesMasterIdLst = prs_elm.notesMasterIdLst
+        assert notesMasterIdLst is not None
+        notesMasterId = notesMasterIdLst.notesMasterId
+        assert notesMasterId is not None
+        assert notesMasterId.rId == "rId42"
 
     def it_provides_access_to_its_notes_master(self, request, notes_master_part_):
         notes_master_ = instance_mock(request, NotesMaster)