Fix Pyreverse duplicate annotations (#9012)

Author: nickdrozd

doc/whatsnew/fragments/8888.bugfix

@@ -0,0 +1,3 @@
+Don't show duplicate type annotations in Pyreverse diagrams.
+
+Closes #8888

pylint/pyreverse/diagrams.py

@@ -178,7 +178,11 @@ def class_names(self, nodes_lst: Iterable[nodes.NodeNG]) -> list[str]:
                     node_name = node.name
                     names.append(node_name)
         # sorted to get predictable (hence testable) results
-        return sorted(names)
+        return sorted(
+            name
+            for name in names
+            if all(name not in other or name == other for other in names)
+        )
 
     def has_node(self, node: nodes.NodeNG) -> bool:
         """Return true if the given node is included in the diagram."""

tests/pyreverse/functional/class_diagrams/attributes/duplicates.mmd

@@ -2,8 +2,8 @@ classDiagram
   class A {
   }
   class DuplicateAnnotations {
-    lav : list, list[str]
-    val : str, str | int
+    lav : list[str]
+    val : str | int
     bar() None
   }
   class DuplicateArrows {

tests/pyreverse/functional/class_diagrams/attributes/duplicates.py

@@ -20,7 +20,7 @@ def __init__(self):
 
 
 
-# OPEN BUG: https://github.com/pylint-dev/pylint/issues/8888
+# Test for https://github.com/pylint-dev/pylint/issues/8888
 class DuplicateAnnotations:
     def __init__(self) -> None:
         self.val: str | int = "1"