Support custom handling of extractor errors

[connec]

Example:

fn main() {
    ...
    App::new().resource("/items", |r| r.with(create_item))
    ...
}

#[derive(Deserialize)]
struct Item {
    ...
}

fn create_item(item: Json<Item>) -> HttpResponse {
    ...
}

Currently, if there is a deserialization error when attempting to extract an Item (e.g. because the JSON payload has missing fields, or is the wrong type) an empty HTTP 400 Bad Request response will be returned due to the impl of ResponseError for DeError.

Whilst this is sufficient for experimental or internal APIs, it would be useful to be able to customise or override how errors are handled. For myself, I wanted to include the text of the serialization error in the response body so consumers can debug their bad requests.

[fafhrd91]

added JsonConfig::error_handler()

[fafhrd91]

you can use this method https://actix.rs/actix-web/actix_web/error/struct.InternalError.html#method.from_response

[connec]

Wow, quick update, thanks! I will give it a try 😄

[fierydrake]

added JsonConfig::error_handler()

moved to here https://actix.rs/actix-web/actix_web/web/struct.JsonConfig.html#method.error_handler

[axic]

Active docs at https://docs.rs/actix-web/latest/actix_web/web/struct.JsonConfig.html#method.error_handler