Error parsing nullable quoted_num

[stephanyuan]

Error parsing nullable quoted_num

[stephenberry]

This does seem like a useful feature to support. Are you also wanting null to be supported because this is an optional? It seems like empty quotes is more of an error and that null would be more appropriate. But, perhaps you're required to handle empty quotes and want to do so with an optional?

[justend29]

I agree - empty strings should by default produce an error when using quoted_num because you are explicitly stating "parse numbers that are enclosed in strings", which an empty string is not.

Nevertheless, handling an explicit null value seems the idiomatic way to convey no value, which is currently not supported with quoted_num. Would adding that support be appropriate?

[stephanyuan]

Yeah, I actually am required to handle empty quotes rather than null, read the doc and thought optional would be my choice. But anyway, I agree on this point that empty quoted_num is more of an error.

Another point would be the inconsistent missing-key-error-handling between string type and quoted_num type when they are defined as nullable.

For example, say I have error_on_missing_keys set to true:

// missing string type key, glz::read returns success
{"num":"123"}  
struct msg1_t {
    std::string                num;
    std::optional<std::string> str;
};

// missing quoted_num type key, glz::read returns missing_key error
{"str":"abc"} 
struct msg2_t {
    std::optional<double> num;
    std::string           str;
};

[stephenberry]

In #932 I merged in support for the major features requested in this issue.

• Wrappers like quoted_num now behave like nullable types when they contain a nullable type
• error_on_missing_keys now doesn't error if the optional is not set, like other nullable types

I did not add support for parsing empty strings as null optionals. I feel like this is a corner case that probably should be handled through a custom parser using glz::custom or glz::to_json/glz::from_json.

I'm going to close this issue because of the major improvements, and if you need assistance creating a custom parser, feel free to post another issue or discussion.