bpo-46434: Handle missing docstrings in pdb help (GH-30705)

(cherry picked from commit 60705cff70576482fea31dcafbf8a37cbb751ea5)

Co-authored-by: Tom Sparrow <793763+sparrowt@users.noreply.github.com>

2 files changed, 24 insertions, 0 deletions

diff --git a/Lib/pdb.py b/Lib/pdb.py
index 9432111..7ab50b4 100755
--- a/Lib/pdb.py
+++ b/Lib/pdb.py
@@ -1493,6 +1493,9 @@ class Pdb(bdb.Bdb, cmd.Cmd):
                 self.error('No help for %r; please do not run Python with -OO '
                            'if you need command help' % arg)
                 return
+            if command.__doc__ is None:
+                self.error('No help for %r; __doc__ string missing' % arg)
+                return
             self.message(command.__doc__.rstrip())
 
     do_h = do_help
diff --git a/Lib/test/test_pdb.py b/Lib/test/test_pdb.py
index d4c037d..6ac1a4a 100644
--- a/Lib/test/test_pdb.py
+++ b/Lib/test/test_pdb.py
@@ -1463,6 +1463,27 @@ def bœr():
         self.assertNotIn(b'SyntaxError', stdout,
                          "Got a syntax error running test script under PDB")
 
+    def test_issue46434(self):
+        # Temporarily patch in an extra help command which doesn't have a
+        # docstring to emulate what happens in an embeddable distribution
+        script = """
+            def do_testcmdwithnodocs(self, arg):
+                pass
+
+            import pdb
+            pdb.Pdb.do_testcmdwithnodocs = do_testcmdwithnodocs
+        """
+        commands = """
+            continue
+            help testcmdwithnodocs
+        """
+        stdout, stderr = self.run_pdb_script(script, commands)
+        output = (stdout or '') + (stderr or '')
+        self.assertNotIn('AttributeError', output,
+                         'Calling help on a command with no docs should be handled gracefully')
+        self.assertIn("*** No help for 'testcmdwithnodocs'; __doc__ string missing", output,
+                      'Calling help on a command with no docs should print an error')
+
     def test_issue13183(self):
         script = """
             from bar import bar