Fix NLOHMANN_DEFINE_TYPE_INTRUSIVE_WITH_DEFAULT with an empty JSON instance

[NissimBendanan]

Do not throw an exception when trying to get default value from empty json
fix the issue #4507

class Foo {
 public:
  NLOHMANN_DEFINE_TYPE_INTRUSIVE_WITH_DEFAULT(Foo, a, b)

  Foo() = default;

  int a{10};
  std::string b{"bar"};

  void log() {
    std::cout << "a: " << a << std::endl;
    std::cout << "b: " << b << std::endl;
  }
};

// with an empty json, an exception is thrown instead of getting default values
static void JsonTest_empty_json() {
  nlohmann::json json{};
  auto foo = Foo(json);
  foo.log();
}

---

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• Changes are described in the pull request, or an existing issue is referenced.
• The test suite compiles and runs without error.
• Code coverage is 100%. Test cases can be added by editing the test suite.
• The source code is amalgamated; that is, after making changes to the sources in the include/nlohmann directory, run make amalgamate to create the single-header files single_include/nlohmann/json.hpp and single_include/nlohmann/json_fwd.hpp. The whole process is described here.

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[NissimBendanan]

@gregmarr I will update the PR according to our decision to change only this macro NLOHMANN_JSON_FROM_WITH_DEFAULT

I will change only this file: include\nlohmann\detail\macro_scope.hpp
I will not touch this one: single_include\nlohmann\json.hpp
right?

should also add a test case or update a previous one?
any clue to do this? in which file? how to compile/run the tests?

Thanks

[gregmarr]

@NissimBendanan
From the checklist in the PR template:

The source code is amalgamated; that is, after making changes to the sources in the include/nlohmann directory, run make amalgamate to create the single-header files single_include/nlohmann/json.hpp and single_include/nlohmann/json_fwd.hpp. The whole process is described here.

[gregmarr]

NLOHMANN_DEFINE_TYPE_INTRUSIVE_WITH_DEFAULT is tested in https://github.com/nlohmann/json/blob/develop/tests/src/unit-udt_macro.cpp

[NissimBendanan]

I pushed a new version where I added a check of an empty json.
@nlohmann @gregmarr can you please review?
Thanks

[github-actions]

🔴 Amalgamation check failed! 🔴

The source code has not been amalgamated. @NissimBendanan
Please read and follow the Contribution Guidelines.

[coveralls]

coverage: 99.639%. remained the same
when pulling 548c47b on NissimBendanan:fix_default_value
into 6057b31 on nlohmann:develop.

[NissimBendanan]

I don't understand how to get rid of those errors. here in Amalgamation check failed! 🔴

Format (1)
2754c2754
< #define NLOHMANN_JSON_FROM_WITH_DEFAULT(v1) nlohmann_json_t.v1 = nlohmann_json_j.value(#v1, nlohmann_json_default_obj.v1);

#define NLOHMANN_JSON_FROM_WITH_DEFAULT(v1) nlohmann_json_t.v1 = !nlohmann_json_j.is_null() ? nlohmann_json_j.value(#v1, nlohmann_json_default_obj.v1) : nlohmann_json_default_obj.v1;
Error: Process completed with exit code 1.

locally the single_include files are generated with success.
so so how to fix all of those errors?

[nlohmann]

Use Astyle 3.1 and run make amalgamate.

[NissimBendanan]

I am using astyle 3.1:

nbendana@tlv-wp4ww:/Projects/json$ astyle --version
Artistic Style Version 3.1
nbendana@tlv-wp4ww:/Projects/json$ make amalgamate
make pretty
make[1]: Entering directory '/home/nbendana/Projects/json'
astyle
--style=allman
--indent=spaces=4
--indent-modifiers
--indent-switches
--indent-preproc-block
--indent-preproc-define
--indent-col1-comments
--pad-oper
--pad-header
--align-pointer=type
--align-reference=type
--add-braces
--convert-tabs
--close-templates
--lineend=linux
--preserve-date
--suffix=none
--formatted
include/nlohmann/adl_serializer.hpp include/nlohmann/byte_container_with_subtype.hpp include/nlohmann/detail/abi_macros.hpp include/nlohmann/detail/conversions/from_json.hpp include/nlohmann/detail/conversions/to_chars.hpp include/nlohmann/detail/conversions/to_json.hpp include/nlohmann/detail/exceptions.hpp include/nlohmann/detail/hash.hpp include/nlohmann/detail/input/binary_reader.hpp 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 include/nlohmann/detail/input/position_t.hpp include/nlohmann/detail/iterators/internal_iterator.hpp include/nlohmann/detail/iterators/iter_impl.hpp include/nlohmann/detail/iterators/iteration_proxy.hpp include/nlohmann/detail/iterators/iterator_traits.hpp include/nlohmann/detail/iterators/json_reverse_iterator.hpp include/nlohmann/detail/iterators/primitive_iterator.hpp include/nlohmann/detail/json_custom_base_class.hpp include/nlohmann/detail/json_pointer.hpp include/nlohmann/detail/json_ref.hpp include/nlohmann/detail/macro_scope.hpp include/nlohmann/detail/macro_unscope.hpp include/nlohmann/detail/meta/call_std/begin.hpp include/nlohmann/detail/meta/call_std/end.hpp include/nlohmann/detail/meta/cpp_future.hpp include/nlohmann/detail/meta/detected.hpp include/nlohmann/detail/meta/identity_tag.hpp include/nlohmann/detail/meta/is_sax.hpp include/nlohmann/detail/meta/std_fs.hpp include/nlohmann/detail/meta/type_traits.hpp include/nlohmann/detail/meta/void_t.hpp include/nlohmann/detail/output/binary_writer.hpp include/nlohmann/detail/output/output_adapters.hpp include/nlohmann/detail/output/serializer.hpp include/nlohmann/detail/string_concat.hpp include/nlohmann/detail/string_escape.hpp include/nlohmann/detail/value_t.hpp include/nlohmann/json.hpp include/nlohmann/json_fwd.hpp include/nlohmann/ordered_map.hpp include/nlohmann/thirdparty/hedley/hedley.hpp include/nlohmann/thirdparty/hedley/hedley_undef.hpp tests/abi/config/config.hpp tests/abi/config/custom.cpp tests/abi/config/default.cpp tests/abi/config/noversion.cpp tests/abi/diag/diag.cpp tests/abi/diag/diag.hpp tests/abi/diag/diag_off.cpp tests/abi/diag/diag_on.cpp tests/abi/inline_ns/use_current.cpp tests/abi/inline_ns/use_v3_10_5.cpp tests/abi/main.cpp tests/benchmarks/src/benchmarks.cpp tests/cmake_add_subdirectory/project/main.cpp tests/cmake_fetch_content/project/main.cpp tests/cmake_fetch_content2/project/main.cpp tests/cmake_import/project/main.cpp tests/cmake_import_minver/project/main.cpp tests/cmake_target_include_directories/project/Bar.cpp tests/cmake_target_include_directories/project/Bar.hpp tests/cmake_target_include_directories/project/Foo.cpp tests/cmake_target_include_directories/project/Foo.hpp tests/cmake_target_include_directories/project/main.cpp tests/cuda_example/json_cuda.cu tests/src/fuzzer-driver_afl.cpp tests/src/fuzzer-parse_bjdata.cpp tests/src/fuzzer-parse_bson.cpp tests/src/fuzzer-parse_cbor.cpp tests/src/fuzzer-parse_json.cpp tests/src/fuzzer-parse_msgpack.cpp tests/src/fuzzer-parse_ubjson.cpp tests/src/make_test_data_available.hpp tests/src/test_utils.hpp tests/src/unit-32bit.cpp tests/src/unit-algorithms.cpp tests/src/unit-allocator.cpp tests/src/unit-alt-string.cpp tests/src/unit-assert_macro.cpp tests/src/unit-binary_formats.cpp tests/src/unit-bjdata.cpp tests/src/unit-bson.cpp tests/src/unit-byte_container_with_subtype.cpp tests/src/unit-capacity.cpp tests/src/unit-cbor.cpp tests/src/unit-class_const_iterator.cpp tests/src/unit-class_iterator.cpp tests/src/unit-class_lexer.cpp tests/src/unit-class_parser.cpp tests/src/unit-comparison.cpp tests/src/unit-concepts.cpp tests/src/unit-constructor1.cpp tests/src/unit-constructor2.cpp tests/src/unit-convenience.cpp tests/src/unit-conversions.cpp tests/src/unit-custom-base-class.cpp tests/src/unit-deserialization.cpp tests/src/unit-diagnostics.cpp tests/src/unit-disabled_exceptions.cpp tests/src/unit-element_access1.cpp tests/src/unit-element_access2.cpp tests/src/unit-hash.cpp tests/src/unit-inspection.cpp tests/src/unit-items.cpp tests/src/unit-iterators1.cpp tests/src/unit-iterators2.cpp tests/src/unit-json_patch.cpp tests/src/unit-json_pointer.cpp tests/src/unit-large_json.cpp tests/src/unit-merge_patch.cpp tests/src/unit-meta.cpp tests/src/unit-modifiers.cpp tests/src/unit-msgpack.cpp tests/src/unit-no-mem-leak-on-adl-serialize.cpp tests/src/unit-noexcept.cpp tests/src/unit-ordered_json.cpp tests/src/unit-ordered_map.cpp tests/src/unit-pointer_access.cpp tests/src/unit-readme.cpp tests/src/unit-reference_access.cpp tests/src/unit-regression1.cpp tests/src/unit-regression2.cpp tests/src/unit-serialization.cpp tests/src/unit-testsuites.cpp tests/src/unit-to_chars.cpp tests/src/unit-type_traits.cpp tests/src/unit-ubjson.cpp tests/src/unit-udl.cpp tests/src/unit-udt.cpp tests/src/unit-udt_macro.cpp tests/src/unit-unicode1.cpp tests/src/unit-unicode2.cpp tests/src/unit-unicode3.cpp tests/src/unit-unicode4.cpp tests/src/unit-unicode5.cpp tests/src/unit-user_defined_input.cpp tests/src/unit-windows_h.cpp tests/src/unit-wstring.cpp tests/src/unit.cpp single_include/nlohmann/json.hpp single_include/nlohmann/json_fwd.hpp docs/examples/*.cpp
make[1]: Leaving directory '/home/nbendana/Projects/json'
nbendana@tlv-wp4ww:~/Projects/json$

[NissimBendanan]

for this failure:

ci_static_analysis (ci_test_amalgamation)

I run locally without error:

nbendana@tlv-wp4ww:~/Projects/json$ cmake -S . -B build -DJSON_CI=On
-- Found Python3: /usr/bin/python3 (found version "3.12.3") found components: Interpreter 
-- 🔖 Artistic Style 3.1 (/usr/bin/astyle)
-- 🔖 Clang 18.1.3 (/usr/bin/clang++)
-- 🔖 Clang-Tidy 18.1.3 (/usr/bin/clang-tidy)
-- 🔖 CMake 3.28.3 (/usr/bin/cmake)
-- 🔖 Cppcheck  (CPPCHECK_TOOL-NOTFOUND)
-- 🔖 GCC 13.3.0 (/usr/bin/g++-13)
-- 🔖 GCOV 13.3.0 (/usr/bin/gcov)
-- 🔖 Git 2.43.0 (/usr/bin/git)
-- 🔖 include-what-you-use  (IWYU_TOOL-NOTFOUND)
-- 🔖 Infer  (INFER_TOOL-NOTFOUND)
-- 🔖 LCOV  (LCOV_TOOL-NOTFOUND)
-- 🔖 Ninja 1.11.1 (/usr/bin/ninja)
-- 🔖 OCLint  (OCLINT_TOOL-NOTFOUND)
-- 🔖 Valgrind  (VALGRIND_TOOL-NOTFOUND)
-- Using the multi-header code from /home/nbendana/Projects/json/include/
-- Operating system: Linux-5.15.167.4-microsoft-standard-WSL2; Distributor ID:  Ubuntu; Description:    Ubuntu 24.04.1 LTS; Release:    24.04; Codename:        noble; Linux tlv-wp4ww 5.15.167.4-microsoft-standard-WSL2 #1 SMP Tue Nov 5 00:21:55 UTC 2024 x86_64 x86_64 x86_64 GNU/Linux
-- Compiler: c++ (Ubuntu 13.3.0-6ubuntu2~24.04) 13.3.0; Copyright (C) 2023 Free Software Foundation, Inc.; This is free software; see the source for copying conditions.  There is NO; warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
-- Testing standards: 11 14 17 20 23
-- Configuring done (3.7s)
-- Generating done (0.3s)
-- Build files have been written to: /home/nbendana/Projects/json/build
nbendana@tlv-wp4ww:~/Projects/json$ cmake --build build --target ci_test_amalgamation
Check amalgamation and indentation
Creating amalgamation:
 - processing "include/nlohmann/json.hpp"
...done!


Creating amalgamation:
 - processing "include/nlohmann/json_fwd.hpp"
...done!


Built target ci_test_amalgamation
nbendana@tlv-wp4ww:~/Projects/json$ 

[github-actions]

🔴 Amalgamation check failed! 🔴

The source code has not been amalgamated. @NissimBendanan
Please read and follow the Contribution Guidelines.

[nlohmann]

I am working on #4573 to fix the astyle call.

[nlohmann]

#4573 is merged now. Please update to the latest develop branch and try again.

[NissimBendanan]

after updating with last version, I still have this error:

Formatted  /home/runner/work/json/json/single_include/nlohmann/json.hpp
2764c2764
< #define NLOHMANN_JSON_FROM_WITH_DEFAULT(v1) nlohmann_json_t.v1 = nlohmann_json_j.value(#v1, nlohmann_json_default_obj.v1);
---
> #define NLOHMANN_JSON_FROM_WITH_DEFAULT(v1) nlohmann_json_t.v1 = !nlohmann_json_j.is_null() ? nlohmann_json_j.value(#v1, nlohmann_json_default_obj.v1) : nlohmann_json_default_obj.v1;
gmake[3]: *** [CMakeFiles/ci_test_amalgamation.dir/build.make:80: CMakeFiles/ci_test_amalgamation] Error 1
gmake[2]: *** [CMakeFiles/Makefile2:1484: CMakeFiles/ci_test_amalgamation.dir/all] Error 2
gmake[1]: *** [CMakeFiles/Makefile2:1491: CMakeFiles/ci_test_amalgamation.dir/rule] Error 2
gmake: *** [Makefile:511: ci_test_amalgamation] Error 2

Can you please explain what does this error mean? which check generate this error? how to get rid of it?
Thanks

[nlohmann]

You only changed the code in the include folder. From this, the single-header sources in single_include need to be created. This is done by calling make amalgamate. Please execute this step and commit the changes.

[github-actions]

🔴 Amalgamation check failed! 🔴

The source code has not been amalgamated. @NissimBendanan
Please read and follow the Contribution Guidelines.

[NissimBendanan]

so I need also to commit the change in single_include/nlohmann/json.hpp ?
From CONTRIBUTING.md it is not clear that I need to commit the changes of this file, just that it is auto generated ...

[nlohmann]

The contribution guidelines state:

Please do not edit the files single_include/nlohmann/json.hpp and single_include/nlohmann/json_fwd.hpp directly, but change the include/nlohmann sources and regenerate the files by executing make amalgamate.

I am currently revising the guidelines to make this more clear.

[nlohmann]

Looks good to me.

[nlohmann]

Thanks!