Cargo Features

text_placeholder = { version = "0.5.0", default-features = false, features = ["std", "struct_context"] }
default = std

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

std default struct_context?
struct_context = serde, serde_json, std

Optional dependency in order to use structs for context instead of a HashMap.

Features from optional dependencies

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

serde struct_context?
serde_json struct_context?