fix required member check for described structs in parse_into

[Ramya-9353]

Repro: parse_into a described struct whose members are all required, from {"a": 1, "a": 2, "a": 3}. It reports success, and b and c keep whatever the caller's object held. Same for {"a": 2} as the second element of [{"a": 1, "b": 1, "c": "one"}, {"a": 2}] parsed into std::vector<X>.
Cause: activated_ counts values signalled rather than distinct members, and is never cleared, so a repeated key stands in for a missing one, and each object in a sequence starts from the previous object's count.
Fix: record which members have been set, and clear that record in on_object_begin, the way the sequence handler already clears its container in on_array_begin.

[cppalliance-bot]

An automated preview of the documentation is available at https://1182.json.prtest2.cppalliance.org/libs/json/doc/html/index.html

If more commits are pushed to the pull request, the docs will rebuild at the same URL.

2026-08-13 06:48:59 UTC

[cppalliance-bot]

GCOVR code coverage report https://1182.json.prtest2.cppalliance.org/gcovr/index.html
LCOV code coverage report https://1182.json.prtest2.cppalliance.org/genhtml/index.html
Coverage Diff Report https://1182.json.prtest2.cppalliance.org/diff-report/index.html

Build time: 2026-08-13 07:00:22 UTC

[cppalliance-bot]

Benchmark test results. More info at https://benchmark.cppalliance.org/jsonbenchmarks-pullrequests/1182/pullrequest.html

[grisumbras]

I will have to think a bit about this one. I'm not sure we should check for this, because non-unique keys are explicitly discouraged by the RFC. On the other hand, I see the value this adds.

[Ramya-9353]

On the RFC point: fair, though the patch does not actually reject duplicate keys as such. A document with repeated keys still parses so long as every required member is supplied somewhere; a repeat just no longer counts as a second distinct member. The other half of the bug also triggers with entirely unique keys: [{"a": 1, "b": 1, "c": "one"}, {"a": 2}] into std::vector<X> was accepted with the second element's b and c never written, because activated_ carried over the first object's count. Same carryover reaches map values and nested struct members.

[cppalliance-bot]

Benchmark test results. More info at https://benchmark.cppalliance.org/jsonbenchmarks-pullrequests/1182/pullrequest.html

[cppalliance-bot]

Benchmark test results. More info at https://benchmark.cppalliance.org/jsonbenchmarks-pullrequests/1182/pullrequest.html

[grisumbras]

Also, please rebase on current develop, so that CI stops failing.

[Ramya-9353]

Rebased onto current develop.

[cppalliance-bot]

Benchmark test results. More info at https://benchmark.cppalliance.org/jsonbenchmarks-pullrequests/1182/pullrequest.html

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 93.91%. Comparing base (bac1ab9) to head (9e9458f).

Additional details and impacted files

@@           Coverage Diff            @@
##           develop    #1182   +/-   ##
========================================
  Coverage    93.91%   93.91%           
========================================
  Files           91       91           
  Lines         9288     9290    +2     
========================================
+ Hits          8723     8725    +2     
  Misses         565      565           

Files with missing lines	Coverage Δ
include/boost/json/detail/parse_into.hpp	99.33% <100.00%> (+<0.01%)	⬆️

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