Any crate (or plan for a crate) for a serde 1.0 compatible HJSON?

The most advanced work I found on this topic (hjson-rust) seems to have reached a dead end.

Is there another project somewhere ? Are there people working on making a new serde (and derive) compatible crate for HJSON ? Do they need help ?

I'm not familiar with HJSON, but if it's just another serialization format like json, bson, etc then you can write the crate yourself. Have a look at serde.rs for how to go about it.

That's probably what I'll end up doing, as I've already written JSON (de)serializers in other languages, but I wanted to check this wasn't a duplicate effort, especially as HJSON doesn't look as easy to deal with efficiently as JSON.

I just did a quick search on crates.io. Looks like someone already did.

None of those is compatible with serde 1.0, which means for example you can't use the derive.

The crates.io site gives a comprehensive list of all crates that have been uploaded and match the search criteria. So you'll have to either fork one of the crates and make it compatible, or write it yourself.