feat: add MultipleMasterLayoutsError exception and enhance get_master_layout function to handle multiple master layouts

Author: ya7010

src/tppt/exception.py

@@ -73,3 +73,15 @@ def __init__(self, slide_master_name: str) -> None:
     @property
     def message(self) -> str:
         return f"No slide with MasterLayout tag found in {self.slide_master_name}"
+
+
+class MultipleMasterLayoutsError(TpptException, ValueError):
+    """Multiple master layouts defined."""
+
+    def __init__(self, slide_master_name: str, layout_names: list[str]) -> None:
+        self.slide_master_name = slide_master_name
+        self.layout_names = layout_names
+
+    @property
+    def message(self) -> str:
+        return f"Multiple master layouts defined in {self.slide_master_name}: {', '.join(self.layout_names)}"

src/tppt/slide_master.py

@@ -4,6 +4,7 @@
 
 from tppt.exception import (
     MasterLayoutNotFoundError,
+    MultipleMasterLayoutsError,
     SlideMasterAttributeMustBeSlideLayoutError,
     SlideMasterAttributeNotFoundError,
 )
@@ -107,15 +108,25 @@ class DefaultSlideMaster(SlideMaster):
 
 def get_master_layout(slide_master: type[SlideMaster]) -> type[SlideLayout]:
     """Get the slide tagged with MasterLayout."""
+    master_layouts = []
+    master_layout_names = []
+
     for attr_name, annotation in slide_master.__annotations__.items():
         origin = get_origin(annotation)
         if origin is Annotated:
             args = get_args(annotation)
             # Check the class name instead of directly checking the type of args[1]
             if len(args) > 1 and args[1].__class__.__name__ == "MasterLayout":
-                return getattr(slide_master, attr_name)
+                master_layouts.append(getattr(slide_master, attr_name))
+                master_layout_names.append(attr_name)
+
+    if not master_layouts:
+        raise MasterLayoutNotFoundError(slide_master.__name__)
+
+    if len(master_layouts) > 1:
+        raise MultipleMasterLayoutsError(slide_master.__name__, master_layout_names)
 
-    raise MasterLayoutNotFoundError(slide_master.__name__)
+    return master_layouts[0]
 
 
 def get_layouts(slide_master: type[SlideMaster]) -> list[type[SlideLayout]]: