pythongh-113358: Fix rendering tracebacks with exceptions with a brok…

…en __getattr__ (pythonGH-113359)

cherry picked from commit 04fabe2

Adjusted for 3.11, because exception printing also happens in C
code. For simplicity, instead of including the repr of the exception
that happened during __getattr__, this just prints that an error
occured.

Co-authored-by: Jérome Perrin <perrinjerome@gmail.com>
Co-authored-by: Irit Katriel <1055913+iritkatriel@users.noreply.github.com>

Lib/test/test_traceback.py

@@ -1601,6 +1601,21 @@ def __repr__(self):
         err_msg = '<note str() failed>'
         self.assertEqual(self.get_report(e), vanilla + err_msg + '\nFinal Note\n')
 
+        # an exception with a broken __getattr__ raising a non expected error
+        class BrokenException(Exception):
+            broken = False
+            def __getattr__(self, name):
+                if self.broken:
+                    raise ValueError(f'no {name}')
+                raise AttributeError(name)
+
+        e = BrokenException(123)
+        vanilla = self.get_report(e)
+        e.broken = True
+        self.assertEqual(
+            self.get_report(e),
+            vanilla + "Ignored error getting __notes__\n")
+
     def test_exception_with_multiple_notes(self):
         for e in [ValueError(42), SyntaxError('bad syntax')]:
             with self.subTest(e=e):

Lib/traceback.py

@@ -733,7 +733,10 @@ def __init__(self, exc_type, exc_value, exc_traceback, *, limit=None,
         # Capture now to permit freeing resources: only complication is in the
         # unofficial API _format_final_exc_line
         self._str = _safe_string(exc_value, 'exception')
-        self.__notes__ = getattr(exc_value, '__notes__', None)
+        try:
+            self.__notes__ = getattr(exc_value, '__notes__', None)
+        except Exception as e:
+            self.__notes__ = ['Ignored error getting __notes__']
 
         if exc_type and issubclass(exc_type, SyntaxError):
             # Handle SyntaxError's specially

Misc/NEWS.d/next/Library/2023-12-21-14-55-06.gh-issue-113358.nRkiSL.rst

@@ -0,0 +1 @@
+Fix rendering tracebacks with exceptions with a broken __getattr__

Python/pythonrun.c

@@ -1219,7 +1219,11 @@ print_exception(struct exception_print_context *ctx, PyObject *value)
     /* grab the type and notes now because value can change below */
     PyObject *type = (PyObject *) Py_TYPE(value);
     if (_PyObject_LookupAttr(value, &_Py_ID(__notes__), &notes) < 0) {
-        goto error;
+        PyErr_Clear();
+        notes = Py_BuildValue("[s]", "Ignored error getting __notes__");
+        if (notes == NULL) {
+            goto error;
+        }
     }
 
     if (print_exception_file_and_line(ctx, &value) < 0) {