gh-80731: Avoid executing code in except block in cmd (GH-111740)

Lib/cmd.py

@@ -210,9 +210,8 @@ class Cmd:
         if cmd == '':
             return self.default(line)
         else:
-            try:
-                func = getattr(self, 'do_' + cmd)
-            except AttributeError:
+            func = getattr(self, 'do_' + cmd, None)
+            if func is None:
                 return self.default(line)
             return func(arg)
 

Lib/test/test_cmd.py

@@ -244,6 +244,21 @@ class TestAlternateInput(unittest.TestCase):
              "(Cmd) *** Unknown syntax: EOF\n"))
 
 
+class CmdPrintExceptionClass(cmd.Cmd):
+    """
+    GH-80731
+    cmd.Cmd should print the correct exception in default()
+    >>> mycmd = CmdPrintExceptionClass()
+    >>> try:
+    ...     raise ValueError("test")
+    ... except ValueError:
+    ...     mycmd.onecmd("not important")
+    (<class 'ValueError'>, ValueError('test'))
+    """
+
+    def default(self, line):
+        print(sys.exc_info()[:2])
+
 def load_tests(loader, tests, pattern):
     tests.addTest(doctest.DocTestSuite())
     return tests

Lib/test/test_pdb.py

@@ -2349,6 +2349,31 @@ def test_pdb_issue_gh_108976():
     (Pdb) continue
     """
 
+
+def test_pdb_issue_gh_80731():
+    """See GH-80731
+
+    pdb should correctly print exception info if in an except block.
+
+    >>> with PdbTestInput([  # doctest: +ELLIPSIS
+    ...     'import sys',
+    ...     'sys.exc_info()',
+    ...     'continue'
+    ... ]):
+    ...     try:
+    ...         raise ValueError('Correct')
+    ...     except ValueError:
+    ...         import pdb; pdb.Pdb(nosigint=True, readrc=False).set_trace()
+    ...         pass
+    > <doctest test.test_pdb.test_pdb_issue_gh_80731[0]>(10)<module>()
+    -> pass
+    (Pdb) import sys
+    (Pdb) sys.exc_info()
+    (<class 'ValueError'>, ValueError('Correct'), <traceback object at ...>)
+    (Pdb) continue
+    """
+
+
 def test_pdb_ambiguous_statements():
     """See GH-104301
 

Misc/NEWS.d/next/Library/2023-11-04-21-12-27.gh-issue-80731.Wq51xg.rst

@@ -0,0 +1 @@
+Avoid executing the default function in :class:`cmd.Cmd` in an except block