Can't use with borrowed values in a struct

[kbknapp]

Myself and @savish are working on porting clap to use serde for all the serialization and deserialization in clap v3. Currently, YAML is the most popular format to deserialize from for clap (because it's the only supported way in v2 😜 ). So we started with a YAML test.

When trying to derive Deserialize for clap::App we run into the error about the 'de lifetime:

15 |     let app: App = serde_yaml::from_str(&yml).unwrap();
   |                         ^^^^^^^^^^^^^^^^^^^^
   |
   = note: required because of the requirements on the impl of `for<'de> _IMPL_DESERIALIZE_FOR_Point::_serde::Deserialize<'de>` for `App<'_,'_>`
   = note: required because of the requirements on the impl of `_IMPL_DESERIALIZE_FOR_Point::_serde::de::DeserializeOwned` for `App<'_,'_>`
   = note: required by `serde_yaml::from_str`

However, if we do the exact same test with serde_json (using a JSON document of course) everything works. So no changes to the clap::App struct, just using serde_json instead of serde_yaml it all works.

Version of serde_yaml

0.7.5

May be related to #85?

[dtolnay]

serde_json::from_str and serde_yaml::from_str have different signatures. YAML only supports deserializing owned data for now. I am not planning to work on this myself and I think it would be a fairly large amount of work, but I would happily accept a PR to support deserializing borrowed data.

[kbknapp]

Ah ok thanks! I didn't look at the implementation differences between the two. Perhaps once my workload lessens I can see what it would take to put this together.

[turboladen]

FWIW, I'm running into this as well. I've got a bit of a specialized port of Rails/Ruby's I18n YAML stuff for translating some things for a private crate. Since the data I'm after is really just a static lookup table (that's deserialized from YAML), I was hoping to generate a static struct containing the translations. Just thought I'd leave my use case here in case it helps give some clout to the ticket.

[dtolnay]

I posted a request for implementation for a new backend: dtolnay/request-for-implementation#9.

[dtolnay]

As of 0.9, serde-yaml uses a new YAML backend, which supports this.