From 9f8282de6bdc3e1f976318821ff151ed45fedc56 Mon Sep 17 00:00:00 2001
From: Tian Gao <gaogaotiantian@hotmail.com>
Date: Mon, 9 Oct 2023 01:17:24 -0700
Subject: gh-106670: Set convenience variable for post mortem debugging
 (#110493)

---
 Lib/pdb.py                                                        | 8 ++++++++
 Lib/test/test_pdb.py                                              | 6 ++++++
 .../next/Library/2023-10-07-00-18-40.gh-issue-106670.kCGyRc.rst   | 1 +
 3 files changed, 15 insertions(+)
 create mode 100644 Misc/NEWS.d/next/Library/2023-10-07-00-18-40.gh-issue-106670.kCGyRc.rst

diff --git a/Lib/pdb.py b/Lib/pdb.py
index fd62d24..2cbd6f6 100755
--- a/Lib/pdb.py
+++ b/Lib/pdb.py
@@ -304,6 +304,14 @@ class Pdb(bdb.Bdb, cmd.Cmd):
         # cache it here to ensure that modifications are not overwritten.
         self.curframe_locals = self.curframe.f_locals
         self.set_convenience_variable(self.curframe, '_frame', self.curframe)
+
+        if self._chained_exceptions:
+            self.set_convenience_variable(
+                self.curframe,
+                '_exception',
+                self._chained_exceptions[self._chained_exception_index],
+            )
+
         return self.execRcLines()
 
     # Can be executed earlier than 'setup' if desired
diff --git a/Lib/test/test_pdb.py b/Lib/test/test_pdb.py
index 8fed1d0..b1652e9 100644
--- a/Lib/test/test_pdb.py
+++ b/Lib/test/test_pdb.py
@@ -859,9 +859,11 @@ def test_post_mortem_chained():
     >>> with PdbTestInput([  # doctest: +ELLIPSIS, +NORMALIZE_WHITESPACE
     ...     'exceptions',
     ...     'exceptions 0',
+    ...     '$_exception',
     ...     'up',
     ...     'down',
     ...     'exceptions 1',
+    ...     '$_exception',
     ...     'up',
     ...     'down',
     ...     'exceptions -1',
@@ -882,6 +884,8 @@ def test_post_mortem_chained():
     (Pdb) exceptions 0
     > <doctest test.test_pdb.test_post_mortem_chained[0]>(3)test_function_2()
     -> 1/0
+    (Pdb) $_exception
+    ZeroDivisionError('division by zero')
     (Pdb) up
     > <doctest test.test_pdb.test_post_mortem_chained[1]>(3)test_function_reraise()
     -> test_function_2()
@@ -891,6 +895,8 @@ def test_post_mortem_chained():
     (Pdb) exceptions 1
     > <doctest test.test_pdb.test_post_mortem_chained[1]>(5)test_function_reraise()
     -> raise ZeroDivisionError('reraised') from e
+    (Pdb) $_exception
+    ZeroDivisionError('reraised')
     (Pdb) up
     > <doctest test.test_pdb.test_post_mortem_chained[2]>(5)test_function()
     -> test_function_reraise()
diff --git a/Misc/NEWS.d/next/Library/2023-10-07-00-18-40.gh-issue-106670.kCGyRc.rst b/Misc/NEWS.d/next/Library/2023-10-07-00-18-40.gh-issue-106670.kCGyRc.rst
new file mode 100644
index 0000000..3a06616
--- /dev/null
+++ b/Misc/NEWS.d/next/Library/2023-10-07-00-18-40.gh-issue-106670.kCGyRc.rst
@@ -0,0 +1 @@
+In :mod:`pdb`, set convenience variable ``$_exception`` for post mortem debugging.
-- 
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