darling is a crate for proc macro authors, which enables parsing attributes into structs. It is heavily inspired by serde both in its internals and in its API.
darling provides a set of traits which can be derived or manually implemented.
FromMetaItem is used to extract values from a meta-item in an attribute. Implementations are likely reusable for many libraries, much like FromStr or serde::Deserialize. Trait implementations are provided for primitives, some std types, and some syn types.FromDeriveInput is implemented or derived by each proc-macro crate which depends on darling. This is the root for input parsing; it gets access to the identity, generics, and visibility of the target type, and can specify which attribute names should be parsed or forwarded from the input AST.FromField is implemented or derived by each proc-macro crate which depends on darling. Structs deriving this trait will get access to the identity (if it exists), type, and visibility of the field.```rust,ignore
extern crate darling;
pub struct Lorem {
#[darling(default = "local", rename = "sit")]
ipsum: bool,
#[darling(default)]
dolor: Option
Darling's features are built to work well for real-world projects.
serde.FromDeriveInput and FromField can declare properties named ident, vis, ty, attrs, and generics to automatically get copies of the matching values from the input AST.#[darling(map="path")] to specify a function that runs on the result of parsing a meta-item field. This can change the return type, which enables you to parse to an intermediate form and convert that to the type you need in your struct.#[darling(skip)] to mark a field that shouldn't be read from attribute meta-items.