Optional features are part of the crate — the project should say so

tomveens:

A hint from cargo.toml for rust-analyzer can be used to include optional features. But for that to make sense it should also benefit Cargo, and I don't know enough about Cargo's design to say if that's justified.

I think that default-features-for-development would benefit Cargo workflows, too. In particular, if cargo test enabled those features by default, then cargo test without arguments would be closer to “test everything reasonable”, instead of the status quo of not testing anything that’s an optional feature not enabled by anything in the workspace.