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Look up the key only once in the callback parser's key() #5831

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Merged
nlohmann merged 1 commit into from
Oct 15, 2026
Merged

Look up the key only once in the callback parser's key() #5831

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9 changes: 6 additions & 3 deletions include/nlohmann/detail/input/json_sax.hpp
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Original file line number Diff line number Diff line change
Expand Up @@ -674,16 +674,19 @@ class json_sax_dom_callback_parser
if (keep && ref_stack.back())
{
auto& obj = *ref_stack.back()->m_data.m_value.object;
const auto it = obj.find(val);
if (it != obj.end())
// a single lookup: insert the placeholder, or find the existing member
const auto inserted = obj.emplace(val, discarded);
const auto it = inserted.first;
if (!inserted.second)
{
// this is a duplicate key (legal in JSON); remember its
// current value so it can be restored later if the new
// value is rejected by the callback, instead of being
// erased together with the discarded placeholder
duplicate_key_stash.emplace_back(&(it->second), it->second);
it->second = discarded;
}
object_element = &(obj[val] = discarded);
object_element = &(it->second);
}

return true;
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9 changes: 6 additions & 3 deletions single_include/nlohmann/json.hpp
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