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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-regression3.cpp
+5 -241
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-regression3-cpp<NN>.cpp. This file stays C++11-only.
#include "doctest_compatibility.h"
@@ -48,38 +47,8 @@ using ordered_json = nlohmann::ordered_json;
#include <type_traits>
#include <utility>
#ifdef JSON_HAS_CPP_17
#include <any>
#include <variant>
#endif
#ifdef JSON_HAS_CPP_17
#if __has_include(<optional>)
#include <optional>
#elif __has_include(<experimental/optional>)
#endif
/////////////////////////////////////////////////////////////////////
// for #4804
/////////////////////////////////////////////////////////////////////
using json_4804 = nlohmann::json::with_binary_t<std::vector<std::byte>>;
#endif
#ifdef JSON_HAS_CPP_20
#if __has_include(<span>)
#include <span>
#endif
#endif
// the explicit instantiation for #4825 is in unit-explicit_instantiation.cpp
/////////////////////////////////////////////////////////////////////
// for #4440
/////////////////////////////////////////////////////////////////////
#if JSON_HAS_RANGES == 1
#include <ranges>
#endif
// NLOHMANN_JSON_SERIALIZE_ENUM uses a static std::pair
DOCTEST_CLANG_SUPPRESS_WARNING_PUSH
DOCTEST_CLANG_SUPPRESS_WARNING("-Wexit-time-destructors")
@@ -194,22 +163,6 @@ inline void from_json(const json& j, for_3171_base& tb) // NOLINT(misc-use-inter
tb._from_json(j);
}
/////////////////////////////////////////////////////////////////////
// for #3312
/////////////////////////////////////////////////////////////////////
#ifdef JSON_HAS_CPP_20
struct for_3312
{
std::string name;
};
inline void from_json(const json& j, for_3312& obj) // NOLINT(misc-use-internal-linkage)
{
j.at("name").get_to(obj.name);
}
#endif
/////////////////////////////////////////////////////////////////////
// for #3204
/////////////////////////////////////////////////////////////////////
@@ -273,37 +226,8 @@ struct Example_3810
NLOHMANN_DEFINE_TYPE_NON_INTRUSIVE(Example_3810, bla) // NOLINT(misc-use-internal-linkage)
/////////////////////////////////////////////////////////////////////
// for #4740
/////////////////////////////////////////////////////////////////////
#ifdef JSON_HAS_CPP_17
struct Example_4740
{
std::optional<std::string> host = std::nullopt;
std::optional<int> port = std::nullopt;
NLOHMANN_DEFINE_TYPE_INTRUSIVE_WITH_DEFAULT(Example_4740, host, port)
};
#endif
TEST_CASE("regression tests 3")
{
#if JSON_HAS_FILESYSTEM || JSON_HAS_EXPERIMENTAL_FILESYSTEM
// JSON_HAS_CPP_17 (do not remove; see note at top of file)
SECTION("issue #3070 - Version 3.10.3 breaks backward-compatibility with 3.10.2 ")
{
nlohmann::detail::std_fs::path text_path("/tmp/text.txt");
const json j(text_path);
const auto j_path = j.get<nlohmann::detail::std_fs::path>();
CHECK(j_path == text_path);
#if DOCTEST_CLANG || DOCTEST_GCC >= DOCTEST_COMPILER(8, 4, 0)
// only known to work on Clang and GCC >=8.4
CHECK_THROWS_WITH_AS(nlohmann::detail::std_fs::path(json(1)), "[json.exception.type_error.302] type must be string, but is number", json::type_error);
#endif
}
#endif
SECTION("issue #3077 - explicit constructor with default does not compile")
{
@@ -354,31 +278,6 @@ TEST_CASE("regression tests 3")
CHECK(td.str == "value");
}
#ifdef JSON_HAS_CPP_20
SECTION("issue #3312 - Parse to custom class from unordered_json breaks on G++11.2.0 with C++20")
{
// see test for #3171
const ordered_json j = {{"name", "class"}};
for_3312 obj{};
j.get_to(obj);
CHECK(obj.name == "class");
}
#endif
#if defined(JSON_HAS_CPP_17) && JSON_USE_IMPLICIT_CONVERSIONS
SECTION("issue #3428 - Error occurred when converting nlohmann::json to std::any")
{
const json j;
const std::any a1 = j;
std::any&& a2 = j;
CHECK(a1.type() == typeid(j));
CHECK(a2.type() == typeid(j));
}
#endif
SECTION("issue #3204 - ambiguous regression")
{
const for_3204_bar bar_from_foo([](for_3204_foo) noexcept {}); // NOLINT(performance-unnecessary-value-param)
@@ -421,28 +320,6 @@ TEST_CASE("regression tests 3")
CHECK(oj["test"].dump() == expected);
}
#ifdef JSON_HAS_CPP_17
SECTION("issue #4740 - build issue with std::optional")
{
const auto t1 = Example_4740();
const auto j1 = nlohmann::json(t1);
CHECK(j1.dump() == "{\"host\":null,\"port\":null}");
const auto t2 = j1.get<Example_4740>();
CHECK(!t2.host.has_value());
CHECK(!t2.port.has_value());
// improve coverage
auto t3 = Example_4740();
t3.port = 80;
t3.host = "example.com";
const auto j2 = nlohmann::json(t3);
CHECK(j2.dump() == "{\"host\":\"example.com\",\"port\":80}");
const auto t4 = j2.get<Example_4740>();
CHECK(t4.host.has_value());
CHECK(t4.port.has_value());
}
#endif
#if !defined(_MSVC_LANG)
// MSVC returns garbage on invalid enum values, so this test is excluded
// there.
@@ -457,119 +334,7 @@ TEST_CASE("regression tests 3")
}
#endif
#ifdef JSON_HAS_CPP_17
SECTION("issue #4804: from_cbor incompatible with std::vector<std::byte> as binary_t")
{
const std::vector<std::uint8_t> data = {0x80};
const auto decoded = json_4804::from_cbor(data);
CHECK((decoded == json_4804::array()));
}
#ifndef SKIP_TESTS_FOR_ENUM_SERIALIZATION
SECTION("discussion #4209 - custom BinaryType direct assignment and round-tripping")
{
// Test that assigning a custom BinaryType directly creates a binary value, not an array
const std::vector<std::byte> original{std::byte{1}, std::byte{2}, std::byte{3}};
const json_4804 j = original;
CHECK(j.is_binary());
CHECK(!j.is_array());
// Test round-tripping: extracting the binary value back as the custom container type
const auto extracted = j.get<std::vector<std::byte>>();
CHECK(extracted == original);
// Test that the default json alias behavior is unchanged: std::vector<uint8_t> -> array
const json default_json = std::vector<std::uint8_t> {1, 2, 3};
CHECK(default_json.is_array());
CHECK(!default_json.is_binary());
}
SECTION("discussion #4209 - custom BinaryType extraction from parsed array")
{
// Test that extracting a custom BinaryType from a parsed JSON array still works
// (not just from a binary-typed node)
const auto j = json_4804::parse("[1,2,3]");
CHECK(j.is_array());
CHECK(!j.is_binary());
// Extracting as custom BinaryType should work from arrays
const auto extracted = j.get<std::vector<std::byte>>();
CHECK(extracted.size() == 3);
CHECK(extracted[0] == std::byte{1});
CHECK(extracted[1] == std::byte{2});
CHECK(extracted[2] == std::byte{3});
}
#endif
SECTION("issue #5046 - implicit conversion of return json to std::optional no longer implicit")
{
const json jval{};
auto GetValue = [](const json & valRoot) -> std::optional<json>
{
if (valRoot.contains("default"))
{
return valRoot.at("default");
}
return std::nullopt;
};
auto result = GetValue(jval);
CHECK(!result.has_value());
}
#endif
#if JSON_HAS_RANGES == 1
SECTION("issue #4440 - assert when using std::views::filter and GCC 10")
{
auto noOpFilter = std::views::filter([](auto&&) noexcept
{
return true;
});
json j = {1, 2, 3};
auto filtered = j | noOpFilter;
CHECK(*filtered.begin() == 1);
}
#endif
#if JSON_HAS_RANGE_VIEW_CONVERSION
SECTION("issue #4916 - constructing array from C++20 ranges view does not work")
{
std::vector<int> nums{1, 2, 37, 42, 21};
auto filteredNums = nums | std::views::filter([](int i)
{
return i > 10;
});
json const j(filteredNums);
CHECK(j.type() == json::value_t::array);
CHECK(j == json({37, 42, 21}));
}
#endif
// owning_view is not available in libstdc++ < 12
#if JSON_HAS_RANGE_VIEW_CONVERSION && !(defined(__GLIBCXX__) && _GLIBCXX_RELEASE < 12)
SECTION("issue #4916 - constructing array from prvalue C++20 ranges view (owning_view)")
{
json const j(std::vector<int> {1, 2, 37, 42, 21} | std::views::filter([](int i)
{
return i > 10;
}));
CHECK(j.type() == json::value_t::array);
CHECK(j == json({37, 42, 21}));
}
#endif
#if JSON_HAS_RANGE_VIEW_CONVERSION
SECTION("issue #4916 - constructing array from C++20 transform view (prvalue elements)")
{
std::vector<int> nums{1, 2, 3};
auto t = nums | std::views::transform([](int i) noexcept
{
return i * 2;
});
json const j(t);
CHECK(j.type() == json::value_t::array);
CHECK(j == json({2, 4, 6}));
}
#endif
}
TEST_CASE_TEMPLATE("issue #4798 - nlohmann::json::to_msgpack() encode float NaN as double", T, double, float) // NOLINT(readability-math-missing-parentheses, bugprone-throwing-static-initialization)
@@ -914,7 +679,6 @@ TEST_CASE("issue #5402 - update(merge_objects=true) overwrites a primitive with
CHECK(mixed == json({{"keep", {{"a", 1}, {"b", 2}}}, {"replace", {{"x", 2}}}}));
}
TEST_CASE("regression test #5476 - array type without reserve()")
{
// the capacity reserved for definite-length arrays must not require the