Cargo Features

random-access-disk = { version = "3.0.0", default-features = false, features = ["sparse", "async-std", "tokio"] }
default = async-std, sparse

These default features are set whenever random-access-disk is added without default-features = false somewhere in the dependency tree.

sparse default = libc

Features from optional dependencies

In crates that don't use the dep: syntax, optional dependencies automatically become Cargo features.

async-std default

With default features

tokio implicit feature

With fs and io-util

libc sparse

With default (std)