In RustCrypto we got a request to add no_std tag to our crates. The crates are already added to the no-std category, so on the first glance it looks like a needless duplication of information. But on the other hand, tags are more visible on crates.io and more familiar to users. A significant number of crates uses the no_std tag (948 crates) instead or in addition to the no-std category (8305 crates), including some high profile crates like serde.
What do you think about such duplication? Should it be encouraged or discouraged?
Tags are freeform while categories have a curated set of allowed values. There is no way to prevent this duplication other than to nicely ask everyone who uses the no_std tag to stop doing so.
Yes, this is why I am asking whether such duplication should be discouraged, i.e. that the recommendation for new crates would be to not add duplicating tags and for existing ones to remove them after an appropriate category is introduced.
I think it wouldn't be a good idea to add the no_std tag because it will encourage more duplication. Actually, there is a relatively low number of crates using this tag, and much more using the no-std category. But if you add the no_std tag, it will increase the number of crate using it so it legitimate the duplication. In my mind, it's better to keep only the no-std category - unless everyone agrees on the fact that a tag is more relevant, and everyone use the tag instead of the category.