PEP 736: Add 'How to Teach This' (#3838)

* Minor improvements

* Expand How to Teach This

* Fix explanation of f(*,x)

* Move How to Teach This

* Remove comment about syntax highlighting

* Clarify 'one name'

* Address comments

* Highlighting other references

* Add comment about extending the AST node attributes

* Clarify logic in case of expanding syntax on mouseover

* Fix list format

* Address willingc comments

* Retain 'a very simple' for discussion

* Add 'relatively straightforward'

peps/pep-0736.rst

@@ -145,15 +145,6 @@ Security Implications
 
 There are no security implications for this change.
 
-How to Teach This
-=================
-
-Programmers may learn about this feature as an optional abbreviated syntax where
-keyword arguments are taught. The
-`Python Glossary <https://docs.python.org/3/glossary.html#term-argument>`__ and
-`Tutorial <https://docs.python.org/3/tutorial/controlflow.html#keyword-arguments>`__
-may be updated accordingly.
-
 Prior Art
 =========
 
@@ -200,13 +191,13 @@ The purpose of this exercise was to compute statistics about the prevalence of
 this pattern and should not be interpreted as a recommendation that the proposed
 syntactic sugar should be applied universally.
 
-===================================================================== =============== ================ ============== ==============
+===================================================================== =============== ================ ============= ==============
 Statistic                                                             `polars <a_>`__ `fastapi <b_>`__ `rich <c_>`__ `httpx <d_>`__
-===================================================================== =============== ================ ============== ==============
+===================================================================== =============== ================ ============= ==============
 Number of keyword arguments of the form ``f(x=x)`` at invocation      1,654           1,408            566           759
 Percentage of keyword arguments of the form ``f(x=x)`` at invocation  15.83%          28.11%           15.74%        45.13%
 Lines saved                                                           170             35               62            117
-===================================================================== =============== ================ ============== ==============
+===================================================================== =============== ================ ============= ==============
 
 .. _a: https://github.com/joshuabambrick/polars/pull/1
 .. _b: https://github.com/joshuabambrick/fastapi/pull/1
@@ -214,7 +205,8 @@ Lines saved                                                           170
 .. _d: https://github.com/joshuabambrick/httpx/pull/1
 
 Based on this, we note that the ``f(x=x)`` keyword argument pattern is
-widespread, accounting for 10-20% of all keyword argument uses.
+widespread, accounting for anywhere from 15% to just below half of all keyword
+argument uses depending on the codebase.
 
 Proposed Syntax
 ===============
@@ -238,6 +230,43 @@ for the ``f(x=)`` form for the following reasons:
 * `A poll of Python developers <https://discuss.python.org/t/syntactic-sugar-to-encourage-use-of-named-arguments/36217/130>`__
   indicates that this is the most popular syntax among those proposed.
 
+How to Teach This
+=================
+
+To ease the communication of and search for this feature, it may also be
+valuable to provide this feature with a name, such as 'keyword argument
+shorthand'.
+
+Keen Python developers will likely hear about this feature through typical
+information channels, such as newsboards, social media, mailing lists, online
+forums, or word of mouth. Many more will encounter this feature while reading
+code and noting the omission of the value in a keyword argument at invocation,
+violating their expectations. We should ensure such developers have easy access
+to documentation that explains the semantics of this feature and that this
+documentation is easy to find when searching. For example, the
+`Python Glossary <https://docs.python.org/3/glossary.html#term-argument>`__ and
+`Tutorial <https://docs.python.org/3/tutorial/controlflow.html#keyword-arguments>`__
+may be updated accordingly and reasonable keywords may be used to help with
+search discoverability.
+`A StackOverflow question <https://stackoverflow.blog/2011/07/01/its-ok-to-ask-and-answer-your-own-questions/>`__
+could be written to help explain this feature to those searching for an
+explanation.
+
+A teacher may explain this feature to new Python programmers as, "where you see
+an argument followed by an equals sign, such as ``f(x=)``, this represents a
+keyword argument where the name of the argument and its value are the same. This
+can be written equivalently in the expanded notation, ``f(x=x)``." Depending on
+a student's background, a teacher might further compare this to equivalent
+syntax in other languages or Python's f-string syntax ``f"{x=}"``.
+
+To understand this, a student of Python would need to be familiar with the
+basics of functions in addition to the existing keyword argument syntax.
+Given that this feature is a relatively straightforward syntactic sugar, it is
+reasonable that a student who possesses a grasp of keyword arguments will be
+able to absorb this concept quickly. This is evidenced by the success of the
+f-string syntax as well as similar features in other languages (see
+`Prior Art`_).
+
 Rejected Ideas
 ==============
 
@@ -264,10 +293,10 @@ However, we object that:
   positional or named. The ``*`` could easily be missed in a long argument list
   and named arguments may be read as positional or vice versa.
 * It is unclear whether keyword arguments for which the value was not elided may
-  follow the ``*``. If so, then their relative position will be inconsistent but
-  if not, then an arbitrary grouping is enforced between different types of
-  keyword arguments and reordering would be necessary if only one name was
-  changed.
+  follow the ``*``. If so, then their relative position will be confusingly
+  arbitrary, but if not, then an arbitrary grouping is enforced between
+  different types of keyword arguments and reordering of arguments would be
+  necessary if only one name (the argument or its value) was changed.
 * The use of ``*`` in function calls is established and this proposal would
   introduce a new effect which could cause confusion. For example,
   ``f(a, *x, y)`` would mean something different than ``f(a, *, x, y)``.
@@ -455,12 +484,24 @@ One option is to:
 * Jump to the argument in the function definition if the caret/cursor is on the
   argument
 * Jump to the definition of the elided variable if the caret/cursor is on the
-  character following the ``=`` in our proposed syntax.
+  character following the ``=`` in our proposed syntax
 
 Another, potentially complementary, option would be to expand the syntax
 visually on mouseover and enable a ``Ctrl+Click`` (or ``Cmd+Click``) to the
 definition of the variable.
 
+Highlighting other references
+'''''''''''''''''''''''''''''
+
+IDEs frequently highlight matching code references to the value at the current
+caret/cursor position. With this shorthand syntax, when the caret/cursor is on
+the argument name it may be valuable to either:
+
+* Highlight both references to the argument and its value reflecting the fact
+  that this name now refers to both
+* Visually expand the syntax on mouseover (as above) and apply established
+  highlighting logic according to the cursor
+
 Rename symbol
 '''''''''''''
 
@@ -479,7 +520,8 @@ Reference Implementation
 ========================
 
 `A proposed implementation <https://github.com/Hels15/cpython/tree/last-build>`_
-for cpython has been provided by @Hels15.
+for cpython has been provided by @Hels15. We will extend this implementation to
+add an AST node attribute indicating for keywords whether the value was elided.
 
 References
 ==========