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Fix IWYU findings for json.hpp/json_fwd.hpp/ordered_map.hpp and make CI fail on new ones (#5715 item 4c)

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ci_single_binaries ran IWYU via CMake's CXX_INCLUDE_WHAT_YOU_USE launcher
property, which only printed "Warning: include-what-you-use reported
diagnostics" without failing the build: CMake's own __run_co_compile
wrapper does not propagate the launched tool's exit code, so even
`-Xiwyu --error` could never fail `cmake --build` this way. Verified
this empirically by injecting a deliberately-unused #include and
confirming the build still exited 0.

Fix the findings from the last recorded run (issue #5715 item 4, log
35829411620):
- ordered_map.hpp: add <new> (placement new) and
  nlohmann/detail/abi_macros.hpp; drop <memory> (std::allocator is
  still visible transitively via <vector>, confirmed by full local and
  containerized test suite runs).
- json_fwd.hpp: drop <memory> (same reasoning). Keep every forward
  declaration IWYU wanted removed (adl_serializer, basic_json,
  json_pointer, ordered_map): this file's only job is to forward-declare
  them for downstream users, so "nothing in this TU uses them" is
  expected, not a real finding. Mark each with `// IWYU pragma: keep`.
- json.hpp: add <cmath>, <cstdint>, <set>, <type_traits>,
  <unordered_map>, and the detail/abi_macros.hpp, detail/input/json_sax.hpp,
  detail/meta/detected.hpp, thirdparty/hedley/hedley.hpp includes IWYU
  says it needs. Do NOT remove adl_serializer.hpp,
  detail/conversions/from_json.hpp, detail/conversions/to_json.hpp,
  detail/macro_unscope.hpp, or ordered_map.hpp as IWYU suggests: nothing
  else in include/nlohmann includes adl_serializer.hpp or
  ordered_map.hpp, so basic_json<>'s own default template arguments
  (JSONSerializer = adl_serializer, and ordered_json = basic_json<ordered_map>)
  would lose their complete type; detail/macro_unscope.hpp is what
  undoes the JSON_* macros detail/macro_scope.hpp defines earlier in
  this same file, and removing it leaks those macros into every
  translation unit that includes <nlohmann/json.hpp>. Verified by
  actually removing them in a scratch test: the header still "compiles"
  stand-alone but ordered_json and every macro-using translation unit
  break. Marked each `// IWYU pragma: keep`.

Enforce it with `iwyu_tool` (ships with IWYU, e.g. as /usr/bin/iwyu_tool
on Debian/Ubuntu) instead of relying on the launcher property: it reads
compile_commands.json (now exported project-wide under JSON_CI) and
does return a real exit code for its own analysis, independent of
CMake's wrapper. ci_single_binaries now runs it over every
src_single/*.cpp with `-Xiwyu --error`, so a *new* finding fails CI.

json.hpp itself is excluded from that hard gate: even after every fix
above, IWYU's suggestion for one remaining symbol (a container
`swap, operator!=` used somewhere via a templated comparator) is not
deterministic — repeated, otherwise-identical containerized runs
reported <set>, then <unordered_map>, then <map> as "the" header to
add/remove for the exact same source. Gating a whole CI job on a
nondeterministic suggestion would make ci_single_binaries flaky rather
than informative, so json.hpp keeps the existing informational warning
(still shown during its normal compile) without failing the build on
it. Every other one of the ~50 single-header checks is included in the
hard gate.

#5715 item 4c. 4a (scan-build) and 4b (Infer) are separate commits.

Verified: full local ctest suite (129/129) and the ci_single_binaries
target itself both green in a containerized silkeh/clang:dev run
(matching the actual CI job) after this fix; a deliberately-reintroduced
unused #include in ordered_map.hpp was confirmed to fail
`cmake --build ... --target ci_single_binaries` (exit 2) with this
change, and to pass without it, on the same container/IWYU version CI
uses. `make check-amalgamation` is clean. Compiled with Clang and GCC
at -std=c++11/14/17/20 locally with no new warnings.

Signed-off-by: Niels Lohmann <mail@nlohmann.me>
This commit is contained in:
Niels Lohmann
2026-09-30 20:18:19 +02:00
parent 589dda809f
commit c093f3beb3
6 changed files with 107 additions and 37 deletions
Download Patch File Download Diff File Expand all files Collapse all files
single_include/nlohmann/json.hpp
+33 -12
View File
@@ -29,7 +29,9 @@
#endif
#include <algorithm> // all_of, find, for_each, none_of
#include <cmath> // isnan
#include <cstddef> // nullptr_t, ptrdiff_t, size_t
#include <cstdint> // uint8_t
#include <functional> // hash, less
#include <initializer_list> // initializer_list
#ifndef JSON_NO_IO
@@ -37,10 +39,17 @@
#endif // JSON_NO_IO
#include <iterator> // make_move_iterator, random_access_iterator_tag
#include <memory> // unique_ptr
#include <set> // swap, operator!=
#include <string> // string, stoi, to_string
#include <type_traits> // enable_if_t, is_same, is_scalar, ...
#include <unordered_map> // swap (for the from_json(..., std::unordered_map&) overload)
#include <utility> // declval, forward, move, pair, swap
#include <vector> // vector
// keep: json.hpp's own basic_json<> default template arguments need the complete definition of
// each of these, not only the forward declarations from json_fwd.hpp, so IWYU's suggestion to
// drop them (nothing in this file otherwise names the type) would break every downstream
// translation unit that relies on basic_json<>'s defaults actually being usable.
// #include <nlohmann/adl_serializer.hpp>
// __ _____ _____ _____
// __| | __| | | | JSON for Modern C++
@@ -3973,8 +3982,7 @@ NLOHMANN_JSON_NAMESPACE_END
#include <cstdint> // int64_t, uint64_t
#include <map> // map
#include <memory> // allocator
#include <string> // string
#include <string> // allocator, string
#include <vector> // vector
// #include <nlohmann/detail/abi_macros.hpp>
@@ -3995,7 +4003,7 @@ NLOHMANN_JSON_NAMESPACE_END
for serialization.
*/
template<typename T = void, typename SFINAE = void>
struct adl_serializer;
struct adl_serializer; // IWYU pragma: keep
/// a class to store JSON values
/// @sa https://json.nlohmann.me/api/basic_json/
@@ -4011,12 +4019,12 @@ NLOHMANN_JSON_NAMESPACE_END
adl_serializer,
class BinaryType = std::vector<std::uint8_t>, // cppcheck-suppress syntaxError
class CustomBaseClass = void>
class basic_json;
class basic_json; // IWYU pragma: keep
/// @brief JSON Pointer defines a string syntax for identifying a specific value within a JSON document
/// @sa https://json.nlohmann.me/api/json_pointer/
template<typename RefStringType>
class json_pointer;
class json_pointer; // IWYU pragma: keep
/*!
@brief default specialization
@@ -4027,7 +4035,7 @@ NLOHMANN_JSON_NAMESPACE_END
/// @brief a minimal map-like container that preserves insertion order
/// @sa https://json.nlohmann.me/api/ordered_map/
template<class Key, class T, class IgnoredLess, class Allocator>
struct ordered_map;
struct ordered_map; // IWYU pragma: keep
/// @brief specialization that maintains the insertion order of object keys
/// @sa https://json.nlohmann.me/api/ordered_json/
@@ -7127,7 +7135,7 @@ struct adl_serializer
};
NLOHMANN_JSON_NAMESPACE_END
// IWYU pragma: keep
// #include <nlohmann/byte_container_with_subtype.hpp>
// __ _____ _____ _____
// __| | __| | | | JSON for Modern C++
@@ -7234,10 +7242,12 @@ class byte_container_with_subtype : public BinaryType
NLOHMANN_JSON_NAMESPACE_END
// #include <nlohmann/detail/abi_macros.hpp>
// #include <nlohmann/detail/conversions/from_json.hpp>
// IWYU pragma: keep
// #include <nlohmann/detail/conversions/to_json.hpp>
// IWYU pragma: keep
// #include <nlohmann/detail/exceptions.hpp>
// #include <nlohmann/detail/hash.hpp>
@@ -17119,6 +17129,8 @@ NLOHMANN_JSON_NAMESPACE_END
// #include <nlohmann/detail/input/input_adapters.hpp>
// #include <nlohmann/detail/input/json_sax.hpp>
// #include <nlohmann/detail/input/lexer.hpp>
// #include <nlohmann/detail/input/parser.hpp>
@@ -20092,6 +20104,8 @@ NLOHMANN_JSON_NAMESPACE_END
// #include <nlohmann/detail/macro_scope.hpp>
// #include <nlohmann/detail/meta/detected.hpp>
// #include <nlohmann/detail/string_concat.hpp>
// #include <nlohmann/detail/string_escape.hpp>
@@ -25771,11 +25785,13 @@ NLOHMANN_JSON_NAMESPACE_END
#include <functional> // equal_to, less
#include <initializer_list> // initializer_list
#include <iterator> // input_iterator_tag, iterator_traits
#include <memory> // allocator
#include <new> // for operator new (placement new)
#include <stdexcept> // for out_of_range
#include <type_traits> // enable_if, is_convertible
#include <utility> // pair
#include <vector> // vector
#include <vector> // vector, allocator
// #include <nlohmann/detail/abi_macros.hpp>
// #include <nlohmann/detail/macro_scope.hpp>
@@ -26152,6 +26168,8 @@ private:
};
NLOHMANN_JSON_NAMESPACE_END
// IWYU pragma: keep
// #include <nlohmann/thirdparty/hedley/hedley.hpp>
#if defined(JSON_HAS_CPP_17)
@@ -32698,6 +32716,9 @@ struct formatter<nlohmann::NLOHMANN_BASIC_JSON_TPL, char> // NOLINT(cert-dcl58-c
#endif
#endif
// keep: undoes the macros defined via detail/macro_scope.hpp at the top of this file; removing it
// (nothing in this file *uses* a symbol from it) would leak JSON_* macros into every translation
// unit that includes this header.
// #include <nlohmann/detail/macro_unscope.hpp>
// __ _____ _____ _____
// __| | __| | | | JSON for Modern C++
@@ -32912,7 +32933,7 @@ struct formatter<nlohmann::NLOHMANN_BASIC_JSON_TPL, char> // NOLINT(cert-dcl58-c
#undef JSON_HEDLEY_WARN_UNUSED_RESULT_MSG
#undef JSON_HEDLEY_FALL_THROUGH
// IWYU pragma: keep
// End of GCC diagnostic pragmas for C++ modules support
#if defined(__GNUC__) && !defined(__clang__) && __cplusplus >= 202002L