Fix unused-variable false positive when using same name for multiple exceptions (#10436)

Author: zenlyj

doc/whatsnew/fragments/10426.false_positive

@@ -0,0 +1,3 @@
+Fix a false positive for ``unused-variable`` when multiple except handlers bind the same name under a try block.
+
+Closes #10426

pylint/checkers/variables.py

@@ -2843,9 +2843,7 @@ def _check_is_unused(
                 return
 
             # Special case for exception variable
-            if isinstance(stmt.parent, nodes.ExceptHandler) and any(
-                n.name == name for n in stmt.parent.nodes_of_class(nodes.Name)
-            ):
+            if self._is_exception_binding_used_in_handler(stmt, name):
                 return
 
             self.add_message(message_name, args=name, node=stmt)
@@ -2921,6 +2919,15 @@ def _check_unused_arguments(
 
         self.add_message("unused-argument", args=name, node=stmt, confidence=confidence)
 
+    def _is_exception_binding_used_in_handler(
+        self, stmt: nodes.NodeNG, name: str
+    ) -> bool:
+        return (
+            isinstance(stmt.parent, nodes.ExceptHandler)
+            and stmt is stmt.parent.name
+            and any(n.name == name for n in stmt.parent.nodes_of_class(nodes.Name))
+        )
+
     def _check_late_binding_closure(self, node: nodes.Name) -> None:
         """Check whether node is a cell var that is assigned within a containing loop.
 
@@ -3252,6 +3259,8 @@ def _check_globals(self, not_consumed: Consumption) -> None:
             for node in node_lst:
                 if in_type_checking_block(node):
                     continue
+                if self._is_exception_binding_used_in_handler(node, name):
+                    continue
                 self.add_message("unused-variable", args=(name,), node=node)
 
     # pylint: disable = too-many-branches

tests/functional/u/unused/unused_global_variable2.py

@@ -9,3 +9,11 @@
 
 
 VAR = 'pylint'  # [unused-variable]
+
+
+try:
+    pass
+except TypeError as exc:
+    print(exc)
+except ValueError as exc:
+    print(exc)

tests/functional/u/unused/unused_variable.py

@@ -187,6 +187,17 @@ def sibling_except_handlers():
     except ValueError as e:
         print(e)
 
+
+def test_multiple_except_handlers_under_try():
+    try:
+        pass
+    except TypeError as exc:
+        print(exc)
+    except ValueError as exc:
+        print(exc)
+    except ArithmeticError as exc:
+        print(exc)
+
 def func6():
     a = 1
 

tests/functional/u/unused/unused_variable.txt

@@ -26,4 +26,4 @@ unused-variable:150:4:154:26:func4:Unused variable 'error':UNDEFINED
 redefined-outer-name:153:8:154:26:func4:Redefining name 'error' from outer scope (line 150):UNDEFINED
 unused-variable:161:4:162:12:main:Unused variable 'e':UNDEFINED
 undefined-loop-variable:168:10:168:11:main:Using possibly undefined loop variable 'e':UNDEFINED
-unused-variable:217:8:218:16:test_regression_8595:Unused variable 'e':UNDEFINED
+unused-variable:228:8:229:16:test_regression_8595:Unused variable 'e':UNDEFINED