gh-141510: Add PyAnyDict_AsNewDict() function by vstinner · Pull Request #145531 · python/cpython

This PR was big, so I merged unrelated changes as separated changes:

• commit 2cd0ddf fix frozendict.items() ^ frozendict.items().
• commit 0c29f83 modify PyDict_Copy() to no longer accept frozendict

@ZeroIntensity convinced me that supporting frozendict in PyDict_Copy() is a bad idea.

What's the motivation for this change?

When a function using PyDict_Copy() is modified to support frozendict, I have to write code like that:

    PyObject *dict;
    if (PyFrozenDict_Check(orig_dict)) {
        dict = PyDict_New();
        if (dict == NULL) {
            goto error;
        }
        if (PyDict_Merge(dict, orig_dict, 1) < 0) {
            Py_DECREF(dict);
            goto error;
        }
    }
    else {
        dict = PyDict_Copy(orig_dict);
        if (dict == NULL) {
            goto error;
        }
    }

I have to copy/paste this code. I would prefer to have a function doing that: convert a frozendict to a dict, copy a dict, or fail if the argument is not a dict or a frozendict. A dedicated function may be more efficient than PyDict_New()+PyDict_Merge().

Would something like PyAnyDict_AsNewDict be more useful?

Oh, I prefer this function over PyFrozenDict_AsDict().

@ZeroIntensity: What do you think of adding a new PyAnyDict_AsNewDict() function?