diff() compared source/target objects purely by key set, ignoring
relative member order. For ordered_json (insertion-ordered, vector-
backed object_t), two objects that differ only in member order are
unequal via operator==, but diff() never emitted any patch operation
to fix the order, so source.patch(diff(source, target)) == target
could fail to hold.
Fix by detecting when common keys appear in a different relative
order in source vs. target (or when a new key would need to land
somewhere other than the end), and in that case removing and
re-adding the affected keys in target's order, which relies on
patch()'s "add" op appending new keys at the end of an ordered_map.
For plain json (std::map-backed, always key-sorted iteration) this
is a no-op and the original minimal per-key diff path is unchanged.
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
When iteration_proxy_value<iter_impl<ordered_json>> appears in a context
that requires it to be complete (function or lambda parameter), the
compiler instantiates basic_json<ordered_map> and walks into
set_parents(iterator, typename iterator::difference_type)
while iterator is still incomplete, failing with "invalid use of
incomplete type".
basic_json::difference_type is already std::ptrdiff_t, so just naming
the underlying type directly avoids the dependent lookup. Behavior and
ABI are unchanged. This was the approach suggested in the issue thread.
Added a regression case in unit-ordered_json.cpp using the same trigger
pattern (lambda parameter naming the proxy type).
Fixes#3732
Signed-off-by: Akhilesh Arora <akhildawra@gmail.com>
Niels Lohmann
Akhilesh Arora
