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Reduce test compile times (spike)

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Two changes roughly halve the CPU time needed to build the unit tests
(clang 21: ~300 s -> ~150 s, GCC 16: ~750-820 s -> ~395-420 s, Debug):

- Move the C++14/17/20-dependent tests into separate
  unit-<name>-cpp<N>.cpp files. A test file is built for every standard
  whose JSON_HAS_CPP_<N> macro it mentions, so far whole large files were
  rebuilt for C++14/17/20 because of a few #ifdef sections. The main files
  are now built for C++11 only; the ci_test_*_cxx<N> jobs still build
  every file for every standard.

- Add the CMake option JSON_TestUnityBuild (ON by default, OFF with
  MinGW): compatible test files are compiled in batches as one
  translation unit so they share the template instantiations of the
  library. Each file keeps its own CTest test, which runs the batch
  executable filtered to that file's test cases. The binary-format tests
  form an explicit group; the rest is batched by JSON_TestUnityBatchSize.

Fix the name clashes that merging files exposed, document the rules for
test files in tests/README.md, and point CONTRIBUTING.md to it.

Signed-off-by: Niels Lohmann <mail@nlohmann.me>
This commit is contained in:
Niels Lohmann committed 2026-10-09 16:49:45 +02:00
1 parent d33068da73
commit 993e37e7ec
44 files changed
+3965 -2225
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tests/src/unit-conversions1.cpp
+5 -76
View File
@@ -6,12 +6,11 @@
// SPDX-FileCopyrightText: 2013-2026 Niels Lohmann <https://nlohmann.me>
// SPDX-License-Identifier: MIT
// cmake/test.cmake selects the C++ standard versions with which to build a
// unit test based on the presence of JSON_HAS_CPP_<VERSION> macros.
// When using macros that are only defined for particular versions of the standard
// (e.g., JSON_HAS_FILESYSTEM for C++17 and up), please mention the corresponding
// version macro in a comment close by, like this:
// JSON_HAS_CPP_<VERSION> (do not remove; see note at top of file)
// cmake/test.cmake builds a unit test with C++ standards beyond C++11 only if the
// source file mentions the corresponding version macro. To avoid rebuilding this
// large file for every standard, tests that depend on the standard version (e.g.,
// those using JSON_HAS_FILESYSTEM, JSON_HAS_RANGES, or JSON_HAS_THREE_WAY_COMPARISON)
// go into a separate file unit-conversions1-cpp<NN>.cpp. This file stays C++11-only.
#include "doctest_compatibility.h"
@@ -31,25 +30,6 @@ using nlohmann::json;
DOCTEST_CLANG_SUPPRESS_WARNING_PUSH
DOCTEST_CLANG_SUPPRESS_WARNING("-Wexit-time-destructors")
#if (defined(__cplusplus) && __cplusplus >= 201703L) || (defined(_HAS_CXX17) && _HAS_CXX17 == 1) // fix for issue #464
#define JSON_HAS_CPP_17
#define JSON_HAS_CPP_14
#elif (defined(__cplusplus) && __cplusplus >= 201402L) || (defined(_HAS_CXX14) && _HAS_CXX14 == 1)
#define JSON_HAS_CPP_14
#endif
#ifdef JSON_HAS_CPP_17
#if __has_include(<optional>)
#include <optional>
#elif __has_include(<experimental/optional>)
#include <experimental/optional>
#endif
#endif
#if defined(JSON_HAS_CPP_17)
#include <string_view>
#endif
TEST_CASE("value conversion")
{
SECTION("get an object (explicit)")
@@ -519,13 +499,6 @@ TEST_CASE("value conversion")
const std::string s = j.get<std::string>();
CHECK(json(s) == j);
}
#if defined(JSON_HAS_CPP_17)
SECTION("std::string_view")
{
std::string_view const s = j.get<std::string_view>();
CHECK(json(s) == j);
}
#endif
SECTION("exception in case of a non-string type")
{
@@ -551,26 +524,6 @@ TEST_CASE("value conversion")
json(json::value_t::number_float).get<json::string_t>(),
"[json.exception.type_error.302] type must be string, but is number", json::type_error&);
}
#if defined(JSON_HAS_CPP_17)
SECTION("exception in case of a non-string type using string_view")
{
CHECK_THROWS_WITH_AS(json(json::value_t::null).get<std::string_view>(),
"[json.exception.type_error.302] type must be string, but is null", json::type_error&);
CHECK_THROWS_WITH_AS(json(json::value_t::object).get<std::string_view>(),
"[json.exception.type_error.302] type must be string, but is object", json::type_error&);
CHECK_THROWS_WITH_AS(json(json::value_t::array).get<std::string_view>(),
"[json.exception.type_error.302] type must be string, but is array", json::type_error&);
CHECK_THROWS_WITH_AS(json(json::value_t::boolean).get<std::string_view>(),
"[json.exception.type_error.302] type must be string, but is boolean", json::type_error&);
CHECK_THROWS_WITH_AS(json(json::value_t::number_integer).get<std::string_view>(),
"[json.exception.type_error.302] type must be string, but is number", json::type_error&);
CHECK_THROWS_WITH_AS(json(json::value_t::number_unsigned).get<std::string_view>(),
"[json.exception.type_error.302] type must be string, but is number", json::type_error&);
CHECK_THROWS_WITH_AS(json(json::value_t::number_float).get<std::string_view>(),
"[json.exception.type_error.302] type must be string, but is number", json::type_error&);
}
#endif
}
SECTION("get a string (explicit, get_to)")
@@ -591,15 +544,6 @@ TEST_CASE("value conversion")
j.get_to(s);
CHECK(json(s) == j);
}
#if defined(JSON_HAS_CPP_17)
SECTION("std::string_view")
{
std::string const s = "previous value";
std::string_view sv = s;
j.get_to(sv);
CHECK(json(sv) == j);
}
#endif
}
SECTION("get null (explicit)")
@@ -638,14 +582,6 @@ TEST_CASE("value conversion")
CHECK(json(s) == j);
}
#if defined(JSON_HAS_CPP_17)
SECTION("std::string_view")
{
std::string_view const s = j.get<std::string_view>();
CHECK(json(s) == j);
}
#endif
SECTION("std::string")
{
const std::string s = j;
@@ -1256,11 +1192,4 @@ TEST_CASE("value conversion")
#endif
}
#ifdef JSON_HAS_CPP_17
#undef JSON_HAS_CPP_17
#endif
#ifdef JSON_HAS_CPP_14
#undef JSON_HAS_CPP_14
#endif
DOCTEST_CLANG_SUPPRESS_WARNING_POP