Niels Lohmann 99716a5ade Keep multimaps with enum keys as arrays of pairs ...

With JSON_USE_OBJECTS_FOR_ENUM_KEYED_MAPS, is_enum_keyed_map also matched
std::multimap and std::unordered_multimap. Storing them as objects throws
type_error.318 as soon as a key occurs twice, which is the normal case for
a multimap, so such values could no longer be serialized at all once the
macro was enabled, although they are stored losslessly as arrays of
[key, value] pairs without it.

Exclude maps with non-unique keys from is_enum_keyed_map. They are
detected by insert(value_type) returning an iterator rather than a
pair<iterator, bool>. Map-like types without such an insert() are still
treated as before.

Signed-off-by: Niels Lohmann <mail@nlohmann.me>

2026-09-27 18:24:48 +02:00

..

nlohmann

Keep multimaps with enum keys as arrays of pairs

2026-09-27 18:24:48 +02:00