On Mon, 19 Jul 2021 at 21:32, Petr Viktorin <encukou@gmail.com> wrote:
> The proposal assumes that in the future, ``PyLocals_Get``, and thus
> ``locals()``, will never gain another kind of return value, however
> unlikely that is.
> AFAICS, code that uses this will usually check for a single special case
> and fall back (or error) for the other(s), so I think it'd be reasonable
> to make this an "enum" with two values. e.g.:
>
> int PyLocals_GetReturnBehavior();  # better name?
> #define PyLocals_DIRECT_REFERENCE 0
> #define PyLocals_SHALLOW_COPY 1

After looking at PyUnicode_Kind, PySendResult, and other already
public enums for inspiration, my proposed spelling is as follows:

====================
typedef enum {
    PyLocals_UNDEFINED = -1;
    PyLocals_DIRECT_REFERENCE = 0,
    PyLocals_SHALLOW_COPY = 1
} PyLocals_Kind;

PyLocals_Kind PyLocals_GetKind(void);
PyLocals_Kind PyFrame_GetLocalsKind(PyFrameObject *);
====================

The PyLocals_UNDEFINED case comes from PyLocals_GetKind() needing an
error value to return when the query API is called with no active
thread state.

I've updated the draft reference implementation to use this API, and
added the associated PEP changes to the review PR at
https://github.com/python/peps/pull/2038/files

Cheers,
Nick.

--
Nick Coghlan   |   ncoghlan@gmail.com   |   Brisbane, Australia
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