build(json): migrate nlohmann/json → Glaze v7.6.0 (~9-15x parse speedup)#7
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…dup)
Replaces the nlohmann/json v3.11.3 FetchContent dep with Glaze v7.6.0.
The public client surface (CDOClient::get_*, DataServiceClient::get_*,
parse_csv_data / parse_ssv_data) is unchanged; internal
`from_json(const nlohmann::json&, T&)` overloads and the transitional
`json_string` / `json_int` / `json_double` / `json_bool` helpers are
replaced with `deserialize_<T>(std::string_view, T&) -> Result<void>`
in the `ncei::` namespace.
Static-shape model structs (Dataset, DataCategory, DataType,
LocationCategory, Location, CDOStation, DataRecord, DatasetField,
DatasetMetadata, DataSearchResult, DatasetSearchResult) get
`glz::meta` specializations in their per-model `.cpp` files. The CDO
list-response envelope (`{metadata: {resultset: {...}}, results:
[...]}`) is parsed via a single templated meta in the internal-only
`src/models/pagination_detail.hpp` — every endpoint shares it. The
DataPoint family (user-driven TMAX/TMIN/PRCP columns -> attribute
pairs) uses `glz::generic` AST walking and is flagged with
`TODO(glaze):` markers.
`ncei::detail::kReadOpts` carries the CDO-friendly opts combo
(`error_on_unknown_keys = false` + `skip_null_members_on_read = true`)
since Glaze v7.6.0's `glz::opts` doesn't ship `skip_null_members_on_read`
as a base-struct member.
Benchmark (x86_64-v3, GCC 13.3, -O3 -DNDEBUG, 21 KB CDO stations
envelope, 1k iters):
- nlohmann/json v3.11.3 : ~360-590 us/op (pre-migration baseline)
- glaze v7.6.0 : ~32-40 us/op (post-migration)
- speedup : 9-15x
Removed `src/core/pagination.cpp` (its `from_json(ResultSetMetadata)`
overload is now redundant — the templated envelope meta handles it).
Added `tests/glaze_test.cpp` (parse-shape parity) and
`tests/parse_benchmark.cpp` (200 us/op regression cap, 30s ctest
timeout).
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Summary
common_glaze_detail.hpp+pagination_detail.hpp(templatedglz::meta<CDOResponseEnvelope<T>>)from_response) ported toglz::genericdispatchCDOClient/DataServiceClientAPI unchangedBenchmark
x86_64-v3, GCC 13.3, -O3 -DNDEBUG, 21 KB CDO
/stations?limit=100envelope, 1k iters:glz::generic fallbacks
DataPoint/DataPointCollection— user-driven TMAX/TMIN/PRCP/SNOW columns sit as siblings to fixed DATE/STATION keys, no staticglz::metapossible. TaggedTODO(glaze):.core/error.cpp::from_response— 3 error shapes (CDO + Data Service + RFC 7807) dispatched via runtime branching.Test plan
make format && make lint && cmake --build build && ctest --output-on-failure166/166 passcpp_auto_auditclean