Problem:
Empty string is a valid JSON key, but json_decode() treats an object
with empty key as ":help msgpack-special-dict". #20757
:echo json_decode('{"": "1"}')
{'_TYPE': [], '_VAL': [['', '1']]}
Note: vim returns `{'': '1'}`.
Solution:
Allow empty string as an object key.
Note that we still (currently) disallow empty keys in object_to_vim() (since 7c01d5ff92):
f64e4b43e1/src/nvim/api/private/converter.c (L333-L334)Fix#20757
Co-authored-by: Justin M. Keyes <justinkz@gmail.com>