From 8d09216470a3af2af03d76db41036d52c6d7e5ad Mon Sep 17 00:00:00 2001
From: Tom Sparrow <793763+sparrowt@users.noreply.github.com>
Date: Fri, 21 Jan 2022 17:00:48 +0000
Subject: [PATCH] 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>
---
 Lib/pdb.py                                    |  3 +++
 Lib/test/test_pdb.py                          | 21 +++++++++++++++++++
 Misc/ACKS                                     |  1 +
 .../2022-01-20-10-35-10.bpo-46434.geS-aP.rst  |  2 ++
 4 files changed, 27 insertions(+)
 create mode 100644 Misc/NEWS.d/next/Library/2022-01-20-10-35-10.bpo-46434.geS-aP.rst

diff --git a/Lib/pdb.py b/Lib/pdb.py
index 943211158ac41e..7ab50b4845d3e6 100755
--- a/Lib/pdb.py
+++ b/Lib/pdb.py
@@ -1493,6 +1493,9 @@ def do_help(self, arg):
                 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 d4c037dabff97e..6ac1a4a3c30255 100644
--- a/Lib/test/test_pdb.py
+++ b/Lib/test/test_pdb.py
@@ -1463,6 +1463,27 @@ def test_issue7964(self):
         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
diff --git a/Misc/ACKS b/Misc/ACKS
index 9292bdc8dc73b7..7f9166cd74cfab 100644
--- a/Misc/ACKS
+++ b/Misc/ACKS
@@ -1668,6 +1668,7 @@ Evgeny Sologubov
 Cody Somerville
 Anthony Sottile
 Edoardo Spadolini
+Tom Sparrow
 Geoffrey Spear
 Clay Spence
 Stefan Sperling
diff --git a/Misc/NEWS.d/next/Library/2022-01-20-10-35-10.bpo-46434.geS-aP.rst b/Misc/NEWS.d/next/Library/2022-01-20-10-35-10.bpo-46434.geS-aP.rst
new file mode 100644
index 00000000000000..6000781fa5aea9
--- /dev/null
+++ b/Misc/NEWS.d/next/Library/2022-01-20-10-35-10.bpo-46434.geS-aP.rst
@@ -0,0 +1,2 @@
+:mod:`pdb` now gracefully handles ``help`` when :attr:`__doc__` is missing,
+for example when run with pregenerated optimized ``.pyc`` files.