attributes serialization

[MarcAntoine-Arnaud]

How to serialise attributes on XML items ?
I d'ont see anything for that. Any suggestion ?

[oli-obk]

Yea attributes are a weird thing. I'm not sure how to handle them. We could rename fields to something like %foo, where the % denotes that the field is meant to be an attribute. This would require one to annotate all attributes, but would work quite nicely I think and remove all confusion we have currently in the deserializer.

[MarcAntoine-Arnaud]

Yep I think like in every library who manage XML ... It's still the same problem of naming.
But yep adding a prefix can made sense (which need to be a parameter) because with that we can generate reversible JSON.

[RReverser]

This would require one to annotate all attributes, but would work quite nicely I think and remove all confusion we have currently in the deserializer.

I agree, also was thinking about this approach to ensure roundtrips. Could avoid most annotations by using something like attr_width vs sub_item by default, but maybe that will be even more verbose?

[oli-obk]

Could avoid most annotations by using something like attr_width vs sub_item by default, but maybe that will be even more verbose?

You mean to require adding % for non-attributes?

[RReverser]

@oli-obk I mean to avoid any annotations and instead use prefixes for struct fields (which is essentially the same, just perhaps more convenient).

[oli-obk]

hmm.. I don't like that, because it exposes xml stuff to users of the struct who don't even care about xml

[RReverser]

Maybe... although author can still add annotations to rename it if it's a public structure / fields and not just for internal usage.

Probably you already know of it, but here there's a nice overview of some of the most common mapping conventions for attributes (and namespaces). The main problem is, there's all kind of conventions. Maybe a plugin system to allow choosing one's preferred method would be best?

[Boscop]

I think an annotation would be a good choice. Maybe #[xml(attribute)].

[oli-obk]

I think an annotation would be a good choice. Maybe #[xml(attribute)].

Serde has no support for such features. serde-xml is just a serde format, we can't create features that serde doesn't have and we can't parse extra attributes.

[oli-obk]

We'll also need to enforce that attribute-fields come before regular fields, because the serializer cannot look ahead. This is probably only doable with a runtime error though.

[anton-dutov]

So, may be like $value, but more complex #[serde(rename = "$xml:attr:name")] #[serde(rename = "$xml:value")]

[Boscop]

@anton-dutov Wouldn't that also affect json serializaton because it's #[serde(rename)]?