Back-annotating the logic errors onto the source JSON file/stream.

[roszakg]

Hi @danielaparker,

I'm looking into back annotating the logical errors into the source JSON file/stream.
If there a way to retrieve the location for a given jsoncons::json/jsoncons::ojscon object?

What would be the canonical way of doing that?
Can I parse whole file and get the location of the given element or do I need to somehow incrementally parse the file and check of application specific errors during the parsing?

Any help would be greatly appreciated.

Thanks,
Grzegorz

[danielaparker]

A basic_json doesn't contain any location information back into the original source.

You could use a filter to examine the json events before they are written into the json document:

#include <jsoncons/json.hpp>

using namespace jsoncons;

int main() 
{
    std::string str = R"({
        "address-book" :
        [
        {
            "name":"Jane Roe",
                "email" : "[email protected]"
        },
        {
             "name":"John",
             "email" : "[email protected]"
        }
        ]
    })";

    class validate_filter : public json_filter
    {
        std::string member_name_;

    public:
        validate_filter(json_visitor& visitor)
            : json_filter(visitor)
        {
        }

    private:
        bool visit_key(const string_view_type& name,
            const ser_context& context,
            std::error_code& ec) override
        {
            member_name_ = name;
            return this->destination().key(name, context, ec);
        }

        bool visit_string(const string_view_type& val,
            semantic_tag tag,
            const ser_context& context,
            std::error_code& ec) override
        {
            if (member_name_ == "name")
            {
                std::size_t end_first = val.find_first_of(" \t");
                std::size_t start_last = val.find_first_not_of(" \t", end_first);
                if (start_last == string_view_type::npos)
                {
                    std::cout << "Incomplete name '" << val
                        << "' at line " << context.line()
                        << " and column " << context.column() << std::endl;
                }
            }
                
            return this->destination().string_value(val, tag, context, ec);
        }
    };

    json_decoder<json> decoder;
    validate_filter filter(decoder);
    json_string_reader reader(str, filter);
    reader.read();

    json doc = decoder.get_result();
}

Output:

Incomplete name 'John' at line 9 and column 27