From e7053b7846d5f1fc0391e8ba75e92fb3cc0ef0ed Mon Sep 17 00:00:00 2001
From: Mark Byrne <mbyrnepr2@gmail.com>
Date: Sat, 7 May 2022 00:26:38 +0200
Subject: [PATCH] Add an exception for `IndexError` inside
 `uninferable_final_decorators` method.

---
 ChangeLog                                     |  2 ++
 doc/whatsnew/2.14.rst                         |  2 ++
 pylint/checkers/utils.py                      |  2 +-
 .../regression_6531_crash_index_error.py      | 28 +++++++++++++++++++
 4 files changed, 33 insertions(+), 1 deletion(-)
 create mode 100644 tests/functional/r/regression/regression_6531_crash_index_error.py

diff --git a/ChangeLog b/ChangeLog
index aec24186b6..c5983fd3a3 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -25,6 +25,8 @@ Release date: TBA
 
   Closes #4301
 
+* Fix ``IndexError`` crash in ``uninferable_final_decorators`` method.
+
 * By default the similarity checker will now ignore imports and ignore function signatures when computing
   duplication. If you want to keep the previous behaviour set ``ignore-imports`` and ``ignore-signatures`` to ``False``.
 
diff --git a/doc/whatsnew/2.14.rst b/doc/whatsnew/2.14.rst
index d59c4792ec..cfb4b57072 100644
--- a/doc/whatsnew/2.14.rst
+++ b/doc/whatsnew/2.14.rst
@@ -305,6 +305,8 @@ Other Changes
 * By default the similarity checker will now ignore imports and ignore function signatures when computing
   duplication. If you want to keep the previous behaviour set ``ignore-imports`` and ``ignore-signatures`` to ``False``.
 
+* Fix ``IndexError`` crash in ``uninferable_final_decorators`` method.
+
 * Pylint now expands the user path (i.e. ``~`` to ``home/yusef/``) and expands environment variables (i.e. ``home/$USER/$project``
   to ``home/yusef/pylint`` for ``USER=yusef`` and ``project=pylint``) for pyreverse's ``output-directory``,
   ``import-graph``, ``ext-import-graph``,  ``int-import-graph`` options, and the spell checker's ``spelling-private-dict-file``
diff --git a/pylint/checkers/utils.py b/pylint/checkers/utils.py
index 5a48ecf0a3..ecb7b68252 100644
--- a/pylint/checkers/utils.py
+++ b/pylint/checkers/utils.py
@@ -850,7 +850,7 @@ def uninferable_final_decorators(
         if isinstance(decorator, nodes.Attribute):
             try:
                 import_node = decorator.expr.lookup(decorator.expr.name)[1][0]
-            except AttributeError:
+            except (AttributeError, IndexError):
                 continue
         elif isinstance(decorator, nodes.Name):
             lookup_values = decorator.lookup(decorator.name)
diff --git a/tests/functional/r/regression/regression_6531_crash_index_error.py b/tests/functional/r/regression/regression_6531_crash_index_error.py
new file mode 100644
index 0000000000..9a2de9cdb4
--- /dev/null
+++ b/tests/functional/r/regression/regression_6531_crash_index_error.py
@@ -0,0 +1,28 @@
+# pylint: disable=missing-docstring, redefined-outer-name
+
+import pytest
+
+
+class Wallet:
+    def __init__(self):
+        self.balance = 0
+
+    def add_cash(self, earned):
+        self.balance += earned
+
+    def spend_cash(self, spent):
+        self.balance -= spent
+
+@pytest.fixture
+def my_wallet():
+    '''Returns a Wallet instance with a zero balance'''
+    return Wallet()
+
+@pytest.mark.parametrize("earned,spent,expected", [
+    (30, 10, 20),
+    (20, 2, 18),
+])
+def test_transactions(my_wallet, earned, spent, expected):
+    my_wallet.add_cash(earned)
+    my_wallet.spend_cash(spent)
+    assert my_wallet.balance == expected