Add a dedicated specification page for name normalization

Author: pradyunsg

source/specifications/declaring-project-metadata.rst

@@ -70,7 +70,7 @@ The complete list of keys allowed in the ``[project]`` table are:
 
 The name of the project.
 
-Tools SHOULD normalize this name, as specified by :pep:`503`, as soon
+Tools SHOULD :ref:`normalize <name-normalization>` this name, as soon
 as it is read for internal consistency.
 
 

source/specifications/index.rst

@@ -15,6 +15,7 @@ Package Distribution Metadata
 .. toctree::
    :maxdepth: 1
 
+   name-normalization
    core-metadata
    version-specifiers
    dependency-specifiers

source/specifications/name-normalization.rst

@@ -0,0 +1,39 @@
+.. _name-normalization:
+
+==========================
+Package name normalization
+==========================
+
+Project names are "normalized" for use in various contexts. This document describes how project names should be normalized.
+
+Valid non-normalized names
+--------------------------
+
+A valid name consists only of ASCII letters and numbers, period,
+underscore and hyphen. It must start and end with a letter or number.
+This means that valid project names are limited to those which match the
+following regex (run with ``re.IGNORECASE``)::
+
+    ^([A-Z0-9]|[A-Z0-9][A-Z0-9._-]*[A-Z0-9])$
+
+Normalization
+-------------
+
+The name should be lowercased with all runs of the characters ``.``, ``-``, or ``_`` replaced with a single ``-`` character. This can be implemented in Python with the re module:
+
+.. code-block:: python
+
+    import re
+
+    def normalize(name):
+        return re.sub(r"[-_.]+", "-", name).lower()
+
+This means that the following names are all equivalent:
+
+* ``friendly-bard``  (normalized form)
+* ``Friendly-Bard``
+* ``FRIENDLY-BARD``
+* ``friendly.bard``
+* ``friendly_bard``
+* ``friendly--bard``
+* ``FrIeNdLy-._.-bArD`` (a _terrible_ way to write a name, but it is valid)