PEP 661: Add missing sections and correctly populate Post-History (#4050)

peps/pep-0661.rst

@@ -6,7 +6,7 @@ Status: Draft
 Type: Standards Track
 Content-Type: text/x-rst
 Created: 06-Jun-2021
-Post-History: 06-Jun-2021
+Post-History: `20-May-2021 <https://discuss.python.org/t/sentinel-values-in-the-stdlib/8810>`__, `06-Jun-2021 <https://discuss.python.org/t/pep-661-sentinel-values/9126>`__
 
 
 TL;DR: See the `Specification`_ and `Reference Implementation`_.
@@ -195,6 +195,35 @@ add minimal complexity.
 Ordering comparisons are undefined for sentinel objects.
 
 
+Backwards Compatibility
+=======================
+
+While not breaking existing code, adding a new "sentinels" stdlib module could
+cause some confusion with regard to existing modules named "sentinels", and
+specifically with the "sentinels" package on PyPI.
+
+The existing "sentinels" package on PyPI [10]_ appears to be abandoned, with
+the latest release being made on Aug. 2016.  Therefore, using this name for a
+new stdlib module seems reasonable.
+
+If and when this PEP is accepted, it may be worth verifying if this has indeed
+been abandoned, and if so asking to transfer ownership to the CPython
+maintainers to reduce the potential for confusion with the new stdlib module.
+
+
+How to Teach This
+=================
+
+The normal types of documentation of new stdlib modules and features, namely
+doc-strings, module docs and a section in "What's New", should suffice.
+
+
+Security Implications
+=====================
+
+This proposal should have no security implications.
+
+
 Reference Implementation
 ========================
 
@@ -385,8 +414,17 @@ Additional Notes
   for these sentinels, where different options were discussed.
 
 
-References
+Open Issues
-==========
+===========
+
+* **Is adding a new stdlib module the right way to go?** I could not find any
+  existing module which seems like a logical place for this.  However, adding
+  new stdlib modules should be done judiciously, so perhaps choosing an
+  existing module would be preferable even if it is not a perfect fit?
+
+
+Footnotes
+=========
 
 .. [1] Python-Dev mailing list: `The repr of a sentinel <https://mail.python.org/archives/list/python-dev@python.org/thread/ZLVPD2OISI7M4POMTR2FCQTE6TPMPTO3/>`_
 .. [2] Python-Dev mailing list: `"The stdlib contains tons of sentinels" <https://mail.python.org/archives/list/python-dev@python.org/message/JBYXQH3NV3YBF7P2HLHB5CD6V3GVTY55/>`_
@@ -397,6 +435,7 @@ References
 .. [7] `Reference implementation at the taleinat/python-stdlib-sentinels GitHub repo <https://github.com/taleinat/python-stdlib-sentinels>`_
 .. [8] `bpo-35712: Make NotImplemented unusable in boolean context <https://github.com/python/cpython/issues/79893>`_
 .. [9] `Discussion thread about type signatures for these sentinels on the typing-sig mailing list <https://mail.python.org/archives/list/typing-sig@python.org/thread/NDEJ7UCDPINP634GXWDARVMTGDVSNBKV/#LVCPTY26JQJW7NKGKGAZXHQKWVW7GOGL>`_
+.. [10] `sentinels package on PyPI <https://pypi.org/project/sentinels/>`_
 
 
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