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#![doc(html_root_url = "https://docs.rs/serde_dhall/0.3.0")] //! [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`][from_str] 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::de::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)?; //! //! 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::de::Result<()> { //! use serde::Deserialize; //! //! #[derive(Debug, 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)?; //! assert_eq!(point.x, 1); //! assert_eq!(point.y, 2); //! //! # Ok(()) //! # } //! ``` //! //! # Type correspondence //! //! The following Dhall types correspond to the following Rust types: //! //! Dhall | Rust //! -------|------ //! `Bool` | `bool` //! `Natural` | `u64`, `u32`, ... //! `Integer` | `i64`, `i32`, ... //! `Double` | `f64`, `f32`, ... //! `Text` | `String` //! `List T` | `Vec<T>` //! `Optional T` | `Option<T>` //! `{ x: T, y: U }` | structs //! `{ _1: T, _2: U }` | `(T, U)`, structs //! `{ x: T, y: T }` | `HashMap<String, T>`, structs //! `< x: T \| y: U >` | enums //! `T -> U` | unsupported //! `Prelude.JSON.Type` | unsupported //! `Prelude.Map.Type T U` | unsupported //! //! //! # 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][from_str]. //! //! [serde_json::from_str]: https://docs.serde.rs/serde_json/de/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, and that it can be deserialized into the required Rust type. However types are //! first-class in Dhall, and this library allows you to additionally check that some 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: you can provide the type as Dhall text or you //! can let Rust infer it for you. //! //! To provide a type written in Dhall, first parse it into a [`serde_dhall::Value`][Value], then //! pass it to [`from_str_check_type`][from_str_check_type]. //! //! ```rust //! # fn main() -> serde_dhall::de::Result<()> { //! use serde_dhall::Value; //! use std::collections::HashMap; //! //! // Parse a Dhall type //! let point_type_str = "{ x: Natural, y: Natural }"; //! let point_type: Value = serde_dhall::from_str(point_type_str)?; //! //! // 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: HashMap<String, usize> = //! serde_dhall::from_str_check_type(point_data, &point_type)?; //! //! 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(()) //! # } //! ``` //! //! You can also let Rust infer the appropriate Dhall type, using the [StaticType] trait. //! //! ```rust //! # fn main() -> serde_dhall::de::Result<()> { //! use serde::Deserialize; //! use serde_dhall::StaticType; //! //! #[derive(Debug, 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: Point = serde_dhall::from_str_auto_type(data)?; //! 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_auto_type::<Point>(invalid_data).is_err()); //! # Ok(()) //! # } //! ``` //! //! [dhall]: https://dhall-lang.org/ //! [serde]: https://docs.serde.rs/serde/ //! [serde::Deserialize]: https://docs.serde.rs/serde/trait.Deserialize.html mod serde; mod static_type; #[doc(inline)] pub use de::{from_str, from_str_auto_type, from_str_check_type}; #[doc(hidden)] pub use dhall_proc_macros::StaticType; pub use static_type::StaticType; #[doc(inline)] pub use value::Value; // A Dhall value. #[doc(hidden)] pub mod value { use dhall::syntax::Builtin; use dhall::{Normalized, NormalizedExpr, Parsed}; use super::de::{Error, Result}; /// A Dhall value #[derive(Debug, Clone, PartialEq, Eq)] pub struct Value(Normalized); impl Value { pub fn from_str(s: &str, ty: Option<&Value>) -> Result<Self> { Value::from_str_using_dhall_error_type(s, ty).map_err(Error::Dhall) } fn from_str_using_dhall_error_type( s: &str, ty: Option<&Value>, ) -> dhall::error::Result<Self> { let resolved = Parsed::parse_str(s)?.resolve()?; let typed = match ty { None => resolved.typecheck()?, Some(t) => resolved.typecheck_with(t.as_normalized())?, }; Ok(Value(typed.normalize())) } pub(crate) fn to_expr(&self) -> NormalizedExpr { self.0.to_expr() } pub(crate) fn as_normalized(&self) -> &Normalized { &self.0 } pub(crate) fn make_builtin_type(b: Builtin) -> Self { Value(Normalized::make_builtin_type(b)) } pub(crate) fn make_optional_type(t: Value) -> Self { Value(Normalized::make_optional_type(t.0)) } pub(crate) fn make_list_type(t: Value) -> Self { Value(Normalized::make_list_type(t.0)) } // Made public for the StaticType derive macro #[doc(hidden)] pub fn make_record_type( kts: impl Iterator<Item = (String, Value)>, ) -> Self { Value(Normalized::make_record_type(kts.map(|(k, t)| (k, t.0)))) } #[doc(hidden)] pub fn make_union_type( kts: impl Iterator<Item = (String, Option<Value>)>, ) -> Self { Value(Normalized::make_union_type( kts.map(|(k, t)| (k, t.map(|t| t.0))), )) } } impl super::de::sealed::Sealed for Value {} impl super::de::Deserialize for Value { fn from_dhall(v: &Value) -> Result<Self> { Ok(v.clone()) } } } /// Deserialize Dhall data to a Rust data structure. pub mod de { use super::StaticType; use super::Value; pub use error::{Error, Result}; mod error { use dhall::error::Error as DhallError; pub type Result<T> = std::result::Result<T, Error>; #[derive(Debug)] #[non_exhaustive] pub enum Error { Dhall(DhallError), Deserialize(String), } impl std::fmt::Display for Error { fn fmt(&self, f: &mut std::fmt::Formatter) -> std::fmt::Result { match self { Error::Dhall(err) => write!(f, "{}", err), Error::Deserialize(err) => write!(f, "{}", err), } } } impl std::error::Error for Error {} impl serde::de::Error for Error { fn custom<T>(msg: T) -> Self where T: std::fmt::Display, { Error::Deserialize(msg.to_string()) } } } pub(crate) mod sealed { pub trait Sealed {} } /// A data structure that can be deserialized from a Dhall expression /// /// This is automatically implemented for any type that [serde][serde] /// can deserialize. /// /// This trait cannot be implemented manually. pub trait Deserialize: sealed::Sealed + Sized { /// See [serde_dhall::from_str][crate::from_str] fn from_dhall(v: &Value) -> Result<Self>; } /// Deserialize an instance of type `T` from a string of Dhall text. /// /// This will recursively resolve all imports in the expression, and /// typecheck it before deserialization. Relative imports will be resolved relative to the /// provided file. More control over this process is not yet available /// but will be in a coming version of this crate. pub fn from_str<T>(s: &str) -> Result<T> where T: Deserialize, { T::from_dhall(&Value::from_str(s, None)?) } /// Deserialize an instance of type `T` from a string of Dhall text, /// additionally checking that it matches the supplied type. /// /// Like [from_str], but this additionally checks that /// the type of the provided expression matches the supplied type. pub fn from_str_check_type<T>(s: &str, ty: &Value) -> Result<T> where T: Deserialize, { T::from_dhall(&Value::from_str(s, Some(ty))?) } /// Deserialize an instance of type `T` from a string of Dhall text, /// additionally checking that it matches the type of `T`. /// /// Like [from_str], but this additionally checks that /// the type of the provided expression matches the output type `T`. The [StaticType] trait /// captures Rust types that are valid Dhall types. pub fn from_str_auto_type<T>(s: &str) -> Result<T> where T: Deserialize + StaticType, { from_str_check_type(s, &<T as StaticType>::static_type()) } }