Using Bytes on a &Vec<u8> field

[theastrallyforged]

.hg If you have, say, macro-generated code that serializes borrowed values, you can't currently use serde_with::Bytes with it (or you have to specialcase Vec<u8> in the macro and map it to [u8])

I did take a shot at implementing this myself, since I figured it'd be pretty simple, but I got stuck at adding a test for it: the test assumes that DeserializeAs is implemented as well as SerializeAs, and while you can deserialize a &[u8], I'm don't think you can deserialize a &Vec<u8>

[jonasbb]

In general, the type you write inside the serde_as attribute should mirror the field type. The only exceptions are the places where you want to change the behavior, such as for Vec<u8> -> Bytes or BTreeMap<X, Y> -> Vec<(X, Y)>. This also applies to references & which should be mirrored too.

This means you can write:

#[serde_as(as = "&Bytes")]
vec: &'a Vec<u8>,

This is possible due to the generic SerializeAs implementation for &T:

serde_with/serde_with/src/ser/impls.rs

Line 32 in 9e952e2

impl<'a, T, U> SerializeAs<&'a T> for &'a U