PEP 685: address more feedback (python#2418)

pep-0685.rst

@@ -50,18 +50,18 @@ Rationale
 This collapses any run of the substitution character down to a single
 character,
 e.g. ``---`` gets collapsed down to ``-``.
-This does not produce a valid Python identifier as specified by the
-core metadata 2.2 specification for extra names.
+This does **not** produce a valid Python identifier as specified by
+the core metadata 2.2 specification for extra names.
 
 `Setuptools 60 does normalization <https://github.com/pypa/setuptools/blob/b2f7b8f92725c63b164d5776f85e67cc560def4e/pkg_resources/__init__.py#L1324-L1330>`__
 via::
 
-    re.sub('[^A-Za-z0-9.-]+', '_', name).lower()
+    re.sub(r'[^A-Za-z0-9-.]+', '_', name).lower()
 
 The use of an underscore/``_`` differs from PEP 503's use of a
 hyphen/``-``.
-Runs of ``_``, unlike PEP 503, do **not** get collapsed,
-e.g. ``___`` stays the same.
+Runs of ``.`` and ``-``, unlike PEP 503, do **not** get collapsed,
+e.g. ``..`` stays the same.
 
 For pip 22, its
 "extra normalisation behaviour is quite convoluted and erratic" [pip-erratic]_,
@@ -80,10 +80,9 @@ using the semantics outlined in `PEP 503 for names <https://peps.python.org/pep-
 
 The `core metadata`_ specification will be updated such that the allowed
 names for `Provides-Extra`_ matches what :pep:`508` specifies for names.
-As this is a superset of what is currently allowed by the core metadata 2.2
-specification,
-it allows for a *loosening* of the naming requirements.
-It will also bring extra naming in line with that of the Name_ field.
+This will bring extra naming in line with that of the Name_ field.
+Because this changes what is considered valid, it will lead to a core
+metadata version increase to ``2.3``.
 
 For tools writing `core metadata`_,
 they MUST write out extra names in their normalized form.
@@ -92,7 +91,15 @@ when used in the `Requires-Dist`_ field.
 
 Tools generating metadata MUST raise an error if a user specified
 two or more extra names which would normalize to the same name.
-Tools SHOULD warn users when an invalid extra name is read.
+Tools generating metadata MUST raise an error if an invalid extra
+name is provided as appropriate for the specified core metadata version.
+If an older core metadata version is specified and the name would be
+invalid with newer core metadata versions,
+tools SHOULD warn the user.
+Tools SHOULD warn users when an invalid extra name is read and not use
+the name to avoid ambiguity.
+Tools MAY raise an error instead of a warning when reading an
+invalid name if they so desire.
 
 
 Backwards Compatibility
@@ -152,12 +159,14 @@ it will also implement this PEP.
 Rejected Ideas
 ==============
 
-Normalize names according to PEP 503
-------------------------------------
+Using setuptools 60's normalization
+-----------------------------------
 
-For backwards-compatibility concerns,
-it was decided not to strictly follow how :pep:`503` normalizes
-distribution names.
+Initially this PEP proposed following setuptools to try and minimize
+backwards-compatibility issues.
+But after checking various wheels on PyPI,
+it became clear that standardizing **all** naming on :pep:`508` and
+:pep:`503` semantics was easier and better long-term.
 
 
 Open Issues