How to avoid Serde needing the Default trait for a field that skips serialization?

Question

I have this struct that is created by deserializing with Serde and I want to have a field of type Url in it which is not deserialized:

#[derive(Deserialize, Debug)]
pub struct Flow {
    #[serde(skip_deserializing)]
    pub source: Url,
}

Playground

Serde complains about Url not satisfying the Default trait. I have tried with and without deriving Default. Is my only option for me to implement the Default trait for Url myself?

Answer 1

You can use #[serde(default = "path")] on the field to give a function with the signature fn() -> Url that should be called if the field is missing.

Answer 2

It's also possible to implement Deserialize yourself and handle missing values appropriately.