NLOHMANN_DEFINE_TYPE_NON_INTRUSIVE_WITH_DEFAULT can not parse { "key" : null}

[engine5d]

Description

struct Data{
std::string key;
}

if json likes
{ "key": null }
the NLOHMANN_DEFINE_TYPE_NON_INTRUSIVE_WITH_DEFAULT to "Data" type occurs exception.

if json like
{ "key" : "" }

it' OK.

Reproduction steps

reproduction ...

Expected vs. actual results

error

Minimal code example

No response

Error messages

No response

Compiler and operating system

win10 vs 2017

Library version

develope

Validation

• The bug also occurs if the latest version from the develop branch is used.
• I can successfully compile and run the unit tests.

[nlohmann]

I assume the exception complains about the type. null cannot be converted into a std::string automatically. If you want to have some custom behavior in this situation (e.g., null converting to the empty string), then you need to define the conversion manually with user-defined to_json/from_json functions.

See https://json.nlohmann.me/api/macros/nlohmann_define_type_non_intrusive/#examples for examples which code the macros create. You can start from there and add your desired behavior.

[nlohmann]

@engine5d Do you need further assistance with this issue?

[engine5d]

thanks. with user-defined to_json/from_json is ok although it's complicated

[wwwtiger2022]

It's better add a flag in these templates, or a new template, to allow json null convert to empty string.