Serde: how to ignore errors?

[matklad]

I am using serde to parse a JSON config. It's important for me that this never fails. Specifically, if a field can't be deserialized because the config is in the wrong format, I want to set this field to config::Default basically. Is it possible to do this with serde?

EDIT: naturally, I also want to collect the list of observed errors, and presnt the to the user

[alice]

You can call unwrap_or_default on the result you got from serde.

[matklad]

That would set all fields to default values, and not only the problematic ones

[elomatreb]

Serde has field attributes to make this possible, either using the regular Default trait impl for the type or with a custom function.

[matklad]

It only helps if attribute is missing, not if it has a wrong format.

Ie, something like this:

// config.rs
struct Config { value:  u32}

// config.json
{
  "value": "92"
}

[alice]

The #[serde(deserialize_with = "path")] attribute can definitely take care of that too, as long as it's valid json.

[matklad]

Hm, indeed the attribute can help, if I annotate each field with the appropriate function, which also will have to duplicate my overall type's default... And I guess I won't get a list of errors that way?

[Hyeonu]

Sure why not

[jethrogb]

You might be able to use DeserializeSeed although I don't really know how it works.