Add exception for finally statements executing before the return

Author: jacobtylerwalls

pylint/checkers/variables.py

@@ -659,9 +659,22 @@ def get_next_to_consume(self, node):
                     )
                     # If the try block returns we assume that assignments in the except
                     # handlers could have happened.
-                    and not any(
-                        isinstance(try_statement, nodes.Return)
-                        for try_statement in n.statement(future=True).parent.parent.body
+                    and (
+                        not any(
+                            isinstance(try_statement, nodes.Return)
+                            for try_statement in n.statement(
+                                future=True
+                            ).parent.parent.body
+                        )
+                        # But not if this node is in the final block, which will
+                        # execute before the return.
+                        or (
+                            isinstance(node_statement.parent, nodes.TryFinally)
+                            and node_statement in node_statement.parent.finalbody
+                            and n.statement(future=True).parent.parent.parent.parent_of(
+                                node_statement
+                            )
+                        )
                     )
                 )
                 or n.statement(future=True).parent.parent_of(node)

tests/functional/u/use/used_before_assignment_except_handler_for_try_with_return.py

@@ -0,0 +1,15 @@
+"""Tests for used-before-assignment with assignments in except handlers after
+try blocks with return statements.
+See: https://github.com/PyCQA/pylint/issues/5500.
+"""
+def function():
+    """Assume except blocks execute if the try block returns."""
+    try:
+        success_message = "success message"
+        return success_message
+    except ValueError:
+        failure_message = "failure message"
+    finally:
+        print(failure_message)  # [used-before-assignment]
+
+    return failure_message

tests/functional/u/use/used_before_assignment_except_handler_for_try_with_return.txt

@@ -0,0 +1 @@
+used-before-assignment:13:14:13:29:function:Using variable 'failure_message' before assignment:UNDEFINED