red citrus
Is it possible to add a proc macro for code that you don't own? for example is there a way i could add a derive macro to some pub struct from another crate? like if i wanted some fn to be called at the beginning of any of the serialize funtions is it even possible to put a derive macro on this struct?
https://docs.rs/serde_json/latest/serde_json/struct.Serializer.html
or maybe there's a trick with newtype to do this?
copper stone
Serde in particular does support this
copper stone
Look into its "remote derive" feature
However, there is no general solution. The derive has to support it
Before you use remote derives, check if the crate has a serde feature, or something related, to turn on derives of their own
red citrus
ah, interesting. I wouldnt have guessed that from the name, but thats really cool.
But as a general answer to the question, that's not something you can usually do, but serde (and some other crates) do allow that?
copper stone
Serde has a slightly weird API for it: it makes you write a copy of the foreign type, put the derive on the copy, and say "this is actually meant to implement for (a newtype around) the foreign type".
It makes sense owing to the limits of what macros can see: only their input.
But it does require some extra work, so it's not that common
