[Question] When using direct parsing, what happens if a key in the JSON is not in the struct?

[DUOLabs333]

Let's say we have struct B. B has three attributes. Now let's say I want to parse_into a string s with 4 keys, and 3 of them are attributes of B. Will the parsing succeed?

[grisumbras]

This is considered an error by the parser.

[DUOLabs333]

Is there a way to turn it off? I have some JSON with some extra keys I use for logging purposes, but shouldn't matter to the underlying struct, as it could change. As far as I can tell, both glaze and daw_json_link support this, but I would like to not have to add another dependency (I'm only direct parsing for some of the JSON strings).

[grisumbras]

The way to allow missing keys is to use an optional as the member's type. E.g.

struct S {
  int n; // required
  std::optional<std::string> s; // not required
};

If that doesn't work for you, you can write a tag_invoke overload and convert with value_to.

[DUOLabs333]

As it turns out, I can rework my system to not have any unused keys, but that could be useful if it later becomes a hard dependency. Thanks.