From a675ee2de1dc78aa8ea38f74a0c692425edf1521 Mon Sep 17 00:00:00 2001
From: Irit Katriel <iritkatriel@yahoo.com>
Date: Mon, 30 Aug 2021 14:47:36 +0100
Subject: [PATCH 1/3] bpo-31299: make it possible to filter out frames from
 tracebacks

---
 Doc/library/traceback.rst  |  3 ++-
 Lib/test/test_traceback.py | 28 ++++++++++++++++++++++++++++
 Lib/traceback.py           |  3 +++
 3 files changed, 33 insertions(+), 1 deletion(-)

diff --git a/Doc/library/traceback.rst b/Doc/library/traceback.rst
index 83d5c8c6fcbd320..e71af262a308657 100644
--- a/Doc/library/traceback.rst
+++ b/Doc/library/traceback.rst
@@ -357,7 +357,8 @@ capture data for later printing in a lightweight fashion.
 
       Returns a string for printing one of the frames involved in the stack.
       This method gets called for each frame object to be printed in the
-      :class:`StackSummary`.
+      :class:`StackSummary`. If it returns ``None``, the frame is omitted
+       from the output.
 
       .. versionadded:: 3.11
 
diff --git a/Lib/test/test_traceback.py b/Lib/test/test_traceback.py
index 5d48e9d7ff0397d..d1967aabb29a1c9 100644
--- a/Lib/test/test_traceback.py
+++ b/Lib/test/test_traceback.py
@@ -1514,6 +1514,34 @@ def some_inner():
             s.format(),
             [f'{__file__}:{some_inner.__code__.co_firstlineno + 1}'])
 
+    def test_dropping_frames(self):
+         def f():
+             1/0
+
+         def g():
+             try:
+                 f()
+             except:
+                 return sys.exc_info()
+
+         exc_info = g()
+
+         class Skip_G(traceback.StackSummary):
+             def format_frame(self, frame):
+                 if frame.name == 'g':
+                     return None
+                 return super().format_frame(frame)
+
+         stack = Skip_G.extract(
+             traceback.walk_tb(exc_info[2])).format()
+
+         self.assertEqual(len(stack), 1)
+         lno = f.__code__.co_firstlineno + 1
+         self.assertEqual(
+             stack[0],
+             f'  File "{__file__}", line {lno}, in f\n    1/0\n'
+         )
+
 
 class TestTracebackException(unittest.TestCase):
 
diff --git a/Lib/traceback.py b/Lib/traceback.py
index 4ad8c9a17b349c1..8d83fd9b517e6ca 100644
--- a/Lib/traceback.py
+++ b/Lib/traceback.py
@@ -515,6 +515,9 @@ def format(self):
         last_name = None
         count = 0
         for frame in self:
+            formatted_frame = self.format_frame(frame)
+            if formatted_frame is None:
+                continue
             if (last_file is None or last_file != frame.filename or
                 last_line is None or last_line != frame.lineno or
                 last_name is None or last_name != frame.name):

From f67d98417ec17f2c0cf78c0c1e6db90a2b461f32 Mon Sep 17 00:00:00 2001
From: "blurb-it[bot]" <43283697+blurb-it[bot]@users.noreply.github.com>
Date: Mon, 30 Aug 2021 13:55:11 +0000
Subject: [PATCH 2/3] =?UTF-8?q?=F0=9F=93=9C=F0=9F=A4=96=20Added=20by=20blu?=
 =?UTF-8?q?rb=5Fit.?=
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

---
 .../NEWS.d/next/Library/2021-08-30-13-55-09.bpo-31299.9QzjZs.rst | 1 +
 1 file changed, 1 insertion(+)
 create mode 100644 Misc/NEWS.d/next/Library/2021-08-30-13-55-09.bpo-31299.9QzjZs.rst

diff --git a/Misc/NEWS.d/next/Library/2021-08-30-13-55-09.bpo-31299.9QzjZs.rst b/Misc/NEWS.d/next/Library/2021-08-30-13-55-09.bpo-31299.9QzjZs.rst
new file mode 100644
index 000000000000000..1ffa0b15172ee73
--- /dev/null
+++ b/Misc/NEWS.d/next/Library/2021-08-30-13-55-09.bpo-31299.9QzjZs.rst
@@ -0,0 +1 @@
+Add option to completely drop frames from a traceback by returning ``None`` from a :meth:`~traceback.StackSummary.format_frame` override.
\ No newline at end of file

From 35616dde763f81ca5b81cfe47ec9e1d1fb03e23b Mon Sep 17 00:00:00 2001
From: Irit Katriel <iritkatriel@yahoo.com>
Date: Mon, 30 Aug 2021 15:05:26 +0100
Subject: [PATCH 3/3] fix whitespace

---
 Doc/library/traceback.rst | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/Doc/library/traceback.rst b/Doc/library/traceback.rst
index e71af262a308657..7b230495b7b564a 100644
--- a/Doc/library/traceback.rst
+++ b/Doc/library/traceback.rst
@@ -358,7 +358,7 @@ capture data for later printing in a lightweight fashion.
       Returns a string for printing one of the frames involved in the stack.
       This method gets called for each frame object to be printed in the
       :class:`StackSummary`. If it returns ``None``, the frame is omitted
-       from the output.
+      from the output.
 
       .. versionadded:: 3.11