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#![doc(html_root_url = "https://docs.rs/serde_dhall/0.6.0")] #![warn(missing_docs, missing_doc_code_examples)] //! [Dhall][dhall] is a programmable configuration language that provides a non-repetitive //! alternative to JSON and YAML. //! //! You can think of Dhall as: JSON + types + imports + functions //! //! For a description of the Dhall language, examples, tutorials, and more, see the [language //! website][dhall]. //! //! This crate provides support for consuming Dhall files the same way you would consume JSON or //! YAML. It uses the [Serde][serde] serialization library to provide drop-in support for Dhall //! for any datatype that supports serde (and that's a lot of them !). //! //! This library is limited to deserializing (reading) Dhall values; serializing (writing) //! values to Dhall is not supported. //! //! # Basic usage //! //! The main entrypoint of this library is the [`from_str`](fn.from_str.html) function. It reads a string //! containing a Dhall expression and deserializes it into any serde-compatible type. //! //! This could mean a common Rust type like `HashMap`: //! //! ```rust //! # fn main() -> serde_dhall::Result<()> { //! use std::collections::HashMap; //! //! // Some Dhall data //! let data = "{ x = 1, y = 1 + 1 } : { x: Natural, y: Natural }"; //! //! // Deserialize it to a Rust type. //! let deserialized_map: HashMap<String, usize> = serde_dhall::from_str(data).parse()?; //! //! let mut expected_map = HashMap::new(); //! expected_map.insert("x".to_string(), 1); //! expected_map.insert("y".to_string(), 2); //! //! assert_eq!(deserialized_map, expected_map); //! # Ok(()) //! # } //! ``` //! //! or a custom datatype, using serde's `derive` mechanism: //! //! ```rust //! # fn main() -> serde_dhall::Result<()> { //! use serde::Deserialize; //! //! #[derive(Deserialize)] //! struct Point { //! x: u64, //! y: u64, //! } //! //! // Some Dhall data //! let data = "{ x = 1, y = 1 + 1 } : { x: Natural, y: Natural }"; //! //! // Convert the Dhall string to a Point. //! let point: Point = serde_dhall::from_str(data).parse()?; //! assert_eq!(point.x, 1); //! assert_eq!(point.y, 2); //! //! # Ok(()) //! # } //! ``` //! //! # Replacing `serde_json` or `serde_yaml` //! //! If you used to consume JSON or YAML, you only need to replace [`serde_json::from_str`] or //! [`serde_yaml::from_str`] with [`serde_dhall::from_str(…).parse()`](fn.from_str.html). //! //! [`serde_json::from_str`]: https://docs.serde.rs/serde_json/fn.from_str.html //! [`serde_yaml::from_str`]: https://docs.serde.rs/serde_yaml/fn.from_str.html //! //! //! # Additional Dhall typechecking //! //! When deserializing, normal type checking is done to ensure that the returned value is a valid //! Dhall value. However types are //! first-class in Dhall, and this library allows you to additionally check that the input data //! matches a given Dhall type. That way, a type error will be caught on the Dhall side, and have //! pretty and explicit errors that point to the source file. //! //! There are two ways to typecheck a Dhall value in this way: you can provide the type manually or //! you can let Rust infer it for you. //! //! To let Rust infer the appropriate Dhall type, use the [StaticType](trait.StaticType.html) //! trait. //! //! ```rust //! # fn main() -> serde_dhall::Result<()> { //! use serde::Deserialize; //! use serde_dhall::StaticType; //! //! #[derive(Deserialize, StaticType)] //! struct Point { //! x: u64, //! y: u64, //! } //! //! // Some Dhall data //! let data = "{ x = 1, y = 1 + 1 }"; //! //! // Convert the Dhall string to a Point. //! let point = serde_dhall::from_str(data) //! .static_type_annotation() //! .parse::<Point>()?; //! assert_eq!(point.x, 1); //! assert_eq!(point.y, 2); //! //! // Invalid data fails the type validation //! let invalid_data = "{ x = 1, z = 0.3 }"; //! assert!( //! serde_dhall::from_str(invalid_data) //! .static_type_annotation() //! .parse::<Point>() //! .is_err() //! ); //! # Ok(()) //! # } //! ``` //! //! To provide a type manually, you need a [`SimpleType`](enum.SimpleType.html) value. You //! can parse it from some Dhall text like you would parse any other value. //! //! ```rust //! # fn main() -> serde_dhall::Result<()> { //! use serde_dhall::SimpleType; //! use std::collections::HashMap; //! //! // Parse a Dhall type //! let point_type_str = "{ x: Natural, y: Natural }"; //! let point_type = serde_dhall::from_str(point_type_str).parse::<SimpleType>()?; //! //! // Some Dhall data //! let point_data = "{ x = 1, y = 1 + 1 }"; //! //! // Deserialize the data to a Rust type. This checks that //! // the data matches the provided type. //! let deserialized_map = serde_dhall::from_str(point_data) //! .type_annotation(&point_type) //! .parse::<HashMap<String, usize>>()?; //! //! let mut expected_map = HashMap::new(); //! expected_map.insert("x".to_string(), 1); //! expected_map.insert("y".to_string(), 2); //! //! assert_eq!(deserialized_map, expected_map); //! # Ok(()) //! # } //! ``` //! //! # Controlling deserialization //! //! If you need more control over the process of reading Dhall values, e.g. disabling //! imports, see the [`Deserializer`] methods. //! //! [`Deserializer`]: struct.Deserializer.html //! [dhall]: https://dhall-lang.org/ //! [serde]: https://docs.serde.rs/serde/ //! [serde::Deserialize]: https://docs.serde.rs/serde/trait.Deserialize.html #[cfg(doctest)] mod test_readme { doc_comment::doctest!("../../README.md"); } mod deserialize; mod error; mod options; mod static_type; /// Dhall values mod value; #[doc(hidden)] pub use dhall_proc_macros::StaticType; pub use deserialize::FromDhall; pub(crate) use deserialize::Sealed; pub(crate) use error::ErrorKind; pub use error::{Error, Result}; pub use options::{from_file, from_str, Deserializer}; pub use static_type::StaticType; pub use value::{SimpleType, Value};