Cargo Features

[dependencies]
target_build_utils = { version = "0.3.1", default-features = false, features = ["serde_json"] }
default = serde_json

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

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_json default

Enables serde_json ^0.9