WIP: respects DefaultVal in schema and adds default value to schema. fixes #679, #396

[autoantwort]

fixes #679, #396

[gemini-code-assist]

Code Review

This pull request introduces support for generating default values in JSON schemas by adding a WithDefault schema type and updating the parsers to extract and serialize default values. However, several critical issues were identified in the review: a compilation failure occurs when a struct contains a mix of DefaultVal and non-DefaultVal fields due to invalid .get() calls on standard types; template deduction and type conversion issues with (void*) nullptr will cause compilation errors in NamedTupleParser::to_schema; and storing default values as std::string leads to double-serialization (e.g., "default": "10" instead of "default": 10) in the output schema.

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[liuzicheng1987]

@autoantwort, I don't think it's a good idea to be trying to fix two problems at once and fixing #396 is tricky. There is a reason no one really took it up in years.

Also I am very concerned about the proposed the solution of passing a void ptr.

I didn't know you were going to propose a fix, so I started working on my own:

#681

This fixes #679, but still needs some adaptions for some non-JSON formats.

[liuzicheng1987]

@autoantwort, if you want to fix #396, I think the best way would be to transform the struct with the default values into an rfl::Generic and then pass that to the to_schema function. That might actually work.

[autoantwort]

@autoantwort, if you want to fix #396, I think the best way would be to transform the struct with the default values into an rfl::Generic and then pass that to the to_schema function. That might actually work.

Yeah that worked.

I didn't know you were going to propose a fix, so I started working on my own: #681

Ok so you want to continue yours and I than rebase this on yours or you use the idea from here in #681 or in a new PR?

[liuzicheng1987]

@autoantwort, I think I can continue on mine to fix #679 and then we can dedicate this PR to fixing #396

[liuzicheng1987]

@autoantwort I have just merged my PR which fixes #679, you can merge main into this branch and then continue working on #396.

[autoantwort]

Done