Cargo Features

[dependencies]
rrr = { version = "0.0.0", default-features = false, features = ["serde1"] }
default = serde1

The serde1 feature is set by default whenever rrr is added without default-features = false somewhere in the dependency tree.

serde1 default = serde

Enables serde of num-rational ^0.3.2

Features from optional dependencies

In crates that don't use the dep: syntax, optional dependencies automatically become Cargo features. These features may have been created by mistake, and this functionality may be removed in the future.

serde serde1