Prost convert

FAQ

Why not use the standard From and TryFrom trait?

We redefine our own conversion trait which might not seem logical.

The main reason is to support removing unwanted optional field

In rust we have

impl<T> From<T> for Option<T> { /**/}

which allows

let o: Option<u8> = Option::from(67);
assert_eq!(Some(67), o);

But if we have

struct U;

impl From<U> for T { /**/}

we don't have

impl<T, U> From<U> for Option<T>
where
    T: From<U>,
{
    fn from(value: U) -> Self {
        Some(value.into())
    }
}

We can't add this impl due to the orphan rule, so we add our own conversion trait. It’s mostly transparent to the user because most of the time it will be impl through a derive macro.

TODO

• impl for NonZero types from the std.
• Explore the possibility to use an associated type for the error.
• impl for Bytes https://docs.rs/prost/latest/prost/trait.Message.html#foreign-impls
• Prost support to switch from HashMap to BTreeMap so we should support BTreeMap also.
• Should we make a blanket impl for all the type in the std that impl From/TryFrom (ex u16 and u32). Useful when we have a native type (u16) that can’t be express in the proto. If we don't control the proto and and they define a uint64 and we want a u16 we could provide conversion too.

License

Licensed under either of

• Apache License, Version 2.0 (LICENSE-APACHE or http://www.apache.org/licenses/LICENSE-2.0)
• MIT license (LICENSE-MIT or http://opensource.org/licenses/MIT)

at your option.

Contribution

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