clarify default behavior of documentation field

[RalfJung]

Cc #11777, rust-lang/crates.io#1484

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[epage]

For myself, I feel like its a bug in the system that we have to add so much nuance here. If that bug isn't being fixed, should we just not reference this and encourage people to set the links?

[ehuss]

Yea, I would agree this seems like weird bug to document. I'm also a little confused, as it seems like the accepted solution should be relatively trivial (something like documentation.or_else(|| format!("https://docs.rs/{name}/latest/{name}")) in the search code).

[RalfJung]

See rust-lang/crates.io#1484, apparently what the crate page does is a lot more complicated than documentation.or_else and involves querying the docs.rs API to check if the crate is actually documented there.

[ehuss]

My comment was based on rust-lang/crates.io#1484 (comment), which says that the search results should not do that query, and instead just always link to the latest version if the documentation field is not specified. That might cause an issue when the docs are not yet ready, or failed to build, but would be no different than if the user specified the documentation field manually.

[RalfJung]

Yeah, agreed.

[weihanglo]

If we agree on seeing a fix on crates.io or other services, should this be closed?