From 1e03fffa850e4a7f87af9a0f530152ebad612455 Mon Sep 17 00:00:00 2001
From: Carl Meyer <carl@oddbird.net>
Date: Wed, 22 Apr 2020 13:24:03 -0600
Subject: [PATCH 1/4] Deprecate lib2to3 module in light of PEP 617.

---
 Doc/library/2to3.rst    | 12 +++++++-----
 Lib/lib2to3/__init__.py |  9 ++++++++-
 2 files changed, 15 insertions(+), 6 deletions(-)

diff --git a/Doc/library/2to3.rst b/Doc/library/2to3.rst
index eb4c9185f48bf2..f21b05ee7a4e38 100644
--- a/Doc/library/2to3.rst
+++ b/Doc/library/2to3.rst
@@ -9,9 +9,7 @@
 of *fixers* to transform it into valid Python 3.x code.  The standard library
 contains a rich set of fixers that will handle almost all code.  2to3 supporting
 library :mod:`lib2to3` is, however, a flexible and generic library, so it is
-possible to write your own fixers for 2to3.  :mod:`lib2to3` could also be
-adapted to custom applications in which Python code needs to be edited
-automatically.
+possible to write your own fixers for 2to3.
 
 
 .. _2to3-using:
@@ -466,9 +464,13 @@ and off individually.  They are described here in more detail.
 
 --------------
 
+.. deprecated:: 3.10
+   Python 3.9 will switch to a PEG parser (see :pep:`617`), and Python 3.10 may
+   include new language syntax that is not parsable by lib2to3's LL(1) parser.
+   The ``lib2to3`` module may be removed from the standard library in a future
+   Python version.
+
 .. note::
 
    The :mod:`lib2to3` API should be considered unstable and may change
    drastically in the future.
-
-.. XXX What is the public interface anyway?
diff --git a/Lib/lib2to3/__init__.py b/Lib/lib2to3/__init__.py
index ea30561d839798..7de54ca9b02fdc 100644
--- a/Lib/lib2to3/__init__.py
+++ b/Lib/lib2to3/__init__.py
@@ -1 +1,8 @@
-#empty
+import warnings
+
+
+warnings.warn(
+    "lib2to3 is deprecated and may not be able to parse Python 3.10+",
+    PendingDeprecationWarning,
+    stacklevel=2,
+)

From eeaf6299454a53ef832fa45099be818fdcc80406 Mon Sep 17 00:00:00 2001
From: "blurb-it[bot]" <43283697+blurb-it[bot]@users.noreply.github.com>
Date: Wed, 22 Apr 2020 20:55:17 +0000
Subject: [PATCH 2/4] =?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/2020-04-22-20-55-17.bpo-40360.Er8sv-.rst | 1 +
 1 file changed, 1 insertion(+)
 create mode 100644 Misc/NEWS.d/next/Library/2020-04-22-20-55-17.bpo-40360.Er8sv-.rst

diff --git a/Misc/NEWS.d/next/Library/2020-04-22-20-55-17.bpo-40360.Er8sv-.rst b/Misc/NEWS.d/next/Library/2020-04-22-20-55-17.bpo-40360.Er8sv-.rst
new file mode 100644
index 00000000000000..290dd453bd4ad9
--- /dev/null
+++ b/Misc/NEWS.d/next/Library/2020-04-22-20-55-17.bpo-40360.Er8sv-.rst
@@ -0,0 +1 @@
+The :mod:`lib2to3` module is pending deprecation due to :pep:`617`.
\ No newline at end of file

From c511f0481d1b9f869c1d8f613db17da38aa06ec9 Mon Sep 17 00:00:00 2001
From: Carl Meyer <carl@oddbird.net>
Date: Wed, 22 Apr 2020 15:04:49 -0600
Subject: [PATCH 3/4] Add links to other options.

---
 Doc/library/2to3.rst | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/Doc/library/2to3.rst b/Doc/library/2to3.rst
index f21b05ee7a4e38..1d7bd262872905 100644
--- a/Doc/library/2to3.rst
+++ b/Doc/library/2to3.rst
@@ -468,9 +468,13 @@ and off individually.  They are described here in more detail.
    Python 3.9 will switch to a PEG parser (see :pep:`617`), and Python 3.10 may
    include new language syntax that is not parsable by lib2to3's LL(1) parser.
    The ``lib2to3`` module may be removed from the standard library in a future
-   Python version.
+   Python version. Consider third-party alternatives such as `LibCST`_ or
+   `parso`_.
 
 .. note::
 
    The :mod:`lib2to3` API should be considered unstable and may change
    drastically in the future.
+
+.. _LibCST: https://libcst.readthedocs.io/
+.. _parso: https://parso.readthedocs.io/

From 3b3dd143ee329a8a587f8d49fba007ffa299a733 Mon Sep 17 00:00:00 2001
From: Carl Meyer <carl@oddbird.net>
Date: Wed, 22 Apr 2020 15:29:37 -0600
Subject: [PATCH 4/4] Fix AllTest.

---
 Lib/lib2to3/__init__.py  | 2 +-
 Lib/test/test___all__.py | 1 +
 2 files changed, 2 insertions(+), 1 deletion(-)

diff --git a/Lib/lib2to3/__init__.py b/Lib/lib2to3/__init__.py
index 7de54ca9b02fdc..4224dffef42957 100644
--- a/Lib/lib2to3/__init__.py
+++ b/Lib/lib2to3/__init__.py
@@ -2,7 +2,7 @@
 
 
 warnings.warn(
-    "lib2to3 is deprecated and may not be able to parse Python 3.10+",
+    "lib2to3 package is deprecated and may not be able to parse Python 3.10+",
     PendingDeprecationWarning,
     stacklevel=2,
 )
diff --git a/Lib/test/test___all__.py b/Lib/test/test___all__.py
index c077881511b8ce..0ba243ee4e74e4 100644
--- a/Lib/test/test___all__.py
+++ b/Lib/test/test___all__.py
@@ -17,6 +17,7 @@ def check_all(self, modname):
         names = {}
         with support.check_warnings(
             (".* (module|package)", DeprecationWarning),
+            (".* (module|package)", PendingDeprecationWarning),
             ("", ResourceWarning),
             quiet=True):
             try: