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Fix problems in PR2117 #2213

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Fix problems in PR2117 #2213

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000c133
fix compiler error C2440 in VS
dota17 Jun 22, 2020
4c4af3b
add travis task : run testcases in C++17
dota17 Jun 24, 2020
e0f6c96
detect the exception in testcase - SECTION("null")
dota17 Jun 24, 2020
7df758f
rename CMAKECXXSTANDARD by CMAKE_CXX_STANDARD
dota17 Jun 28, 2020
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17 changes: 16 additions & 1 deletion .travis.yml
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Original file line number Diff line number Diff line change
Expand Up @@ -218,6 +218,17 @@ matrix:
sources: ['ubuntu-toolchain-r-test']
packages: ['g++-9', 'ninja-build']

- os: linux
compiler: gcc
env:
- COMPILER=g++-9
- CXXFLAGS=-std=c++17
- CMAKECXXSTANDARD=17
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addons:
apt:
sources: ['ubuntu-toolchain-r-test']
packages: ['g++-9', 'ninja-build']

# Linux / Clang

- os: linux
Expand Down Expand Up @@ -328,7 +339,11 @@ script:

# compile and execute unit tests
- mkdir -p build && cd build
- cmake .. ${CMAKE_OPTIONS} -DJSON_MultipleHeaders=${MULTIPLE_HEADERS} -GNinja && cmake --build . --config Release
- if [[ "${CMAKECXXSTANDARD}" != "" ]]; then
cmake .. ${CMAKE_OPTIONS} -DJSON_MultipleHeaders=${MULTIPLE_HEADERS} -DCMAKE_CXX_STANDARD=${CMAKECXXSTANDARD} -GNinja && cmake --build . --config Release ;
else
cmake .. ${CMAKE_OPTIONS} -DJSON_MultipleHeaders=${MULTIPLE_HEADERS} -GNinja && cmake --build . --config Release ;
fi
- ctest -C Release --timeout 2700 -V -j
- cd ..

Expand Down
9 changes: 6 additions & 3 deletions test/src/unit-conversions.cpp
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Expand Up @@ -1710,7 +1710,8 @@ TEST_CASE("std::optional")
std::optional<std::string> opt_null;

CHECK(json(opt_null) == j_null);
CHECK(std::optional<std::string>(j_null) == std::nullopt);
CHECK_THROWS_WITH(std::optional<std::string>(j_null) == std::nullopt,
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Why is null not converted to a nullopt here?

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See 2.b in my comments.

I agree with this view:

The reason is the template optional(U&&) constructor template, which is supposed to activate when T (int) is constructible from U and U is neither std::in_place_t nor optional, and direct-initialize T from it. And so it does, stamping out optional(foo&).

j_null is basic_json, and there is a way that basic_json can be converted to string by calling void from_json(const BasicJsonType& j, typename BasicJsonType::string_t& s)

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This may be a technical explanation, but as I user, when I ask to translate a JSON value to a std::optional<std::string>, then I expect this behavior:

  • string values are stored as value,
  • null is stored as std::nullopt, and
  • all other values throw

At least this is what the code

#ifdef JSON_HAS_CPP_17
template<typename BasicJsonType, typename T>
void from_json(const BasicJsonType& j, std::optional<T>& opt)
{
    if (j.is_null())
    {
        opt = std::nullopt;
    }
    else
    {
        opt = j.template get<T>();
    }
}
#endif

tries to accomplish.

"[json.exception.type_error.302] type must be string, but is null");
}

SECTION("string")
Expand Down Expand Up @@ -1746,7 +1747,8 @@ TEST_CASE("std::optional")
std::vector<std::optional<int>> opt_array = {{1, 2, std::nullopt}};

CHECK(json(opt_array) == j_array);
CHECK(std::vector<std::optional<int>>(j_array) == opt_array);
std::vector<std::optional<int>> tmp = j_array;
CHECK(tmp == opt_array);
}

SECTION("object")
Expand All @@ -1755,7 +1757,8 @@ TEST_CASE("std::optional")
std::map<std::string, std::optional<int>> opt_object {{"one", 1}, {"two", 2}, {"zero", std::nullopt}};

CHECK(json(opt_object) == j_object);
CHECK(std::map<std::string, std::optional<int>>(j_object) == opt_object);
std::map<std::string, std::optional<int>> tmp =j_object;
CHECK(tmp == opt_object);
}
}
#endif