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Diffstat (limited to 'serde_dhall/src/lib.rs')
| -rw-r--r-- | serde_dhall/src/lib.rs | 279 |
1 files changed, 279 insertions, 0 deletions
diff --git a/serde_dhall/src/lib.rs b/serde_dhall/src/lib.rs new file mode 100644 index 0000000..3d07539 --- /dev/null +++ b/serde_dhall/src/lib.rs @@ -0,0 +1,279 @@ +#![feature(non_exhaustive)] + +//! [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 for now. +//! +//! # Examples +//! +//! ### Custom datatype +//! +//! If you have a custom datatype for which you derived [serde::Deserialize], chances are +//! you will be able to derive [StaticType] for it as well. +//! This allows easy type-safe deserializing. +//! +//! ```edition2018 +//! use serde::Deserialize; +//! use serde_dhall::{de::Error, StaticType}; +//! +//! #[derive(Debug, Deserialize, StaticType)] +//! struct Point { +//! x: u64, +//! y: u64, +//! } +//! +//! fn main() -> Result<(), Error> { +//! // 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(()) +//! } +//! ``` +//! +//! ### Loosely typed +//! +//! If you used to consume JSON or YAML in a loosely typed way, you can continue to do so +//! with Dhall. You only need to replace [serde_json::from_str] or [serde_yaml::from_str] +//! with [serde_dhall::from_str][from_str]. +//! More generally, if the [StaticType] derive doesn't suit your +//! needs, you can still deserialize any valid Dhall file that serde can handle. +//! +//! [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 +//! +//! ```edition2018 +//! # fn main() -> serde_dhall::de::Result<()> { +//! use std::collections::BTreeMap; +//! +//! // Some Dhall data +//! let data = "{ x = 1, y = 1 + 1 } : { x: Natural, y: Natural }"; +//! +//! // Deserialize it to a Rust type. +//! let deserialized_map: BTreeMap<String, usize> = serde_dhall::from_str(data)?; +//! +//! let mut expected_map = BTreeMap::new(); +//! expected_map.insert("x".to_string(), 1); +//! expected_map.insert("y".to_string(), 2); +//! +//! assert_eq!(deserialized_map, expected_map); +//! # Ok(()) +//! # } +//! ``` +//! +//! You can alternatively specify a Dhall type that the input should match. +//! +//! ```edition2018 +//! # fn main() -> serde_dhall::de::Result<()> { +//! use std::collections::BTreeMap; +//! +//! // Parse a Dhall type +//! let point_type_str = "{ x: Natural, y: Natural }"; +//! let point_type = 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 ensures that +//! // the data matches the point type. +//! let deserialized_map: BTreeMap<String, usize> = +//! serde_dhall::from_str_check_type(point_data, &point_type)?; +//! +//! let mut expected_map = BTreeMap::new(); +//! expected_map.insert("x".to_string(), 1); +//! expected_map.insert("y".to_string(), 2); +//! +//! assert_eq!(deserialized_map, expected_map); +//! # 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. +pub mod value { + use dhall::phase::{NormalizedExpr, Parsed, Typed}; + use dhall_syntax::Builtin; + + use super::de::{Error, Result}; + + /// A Dhall value + #[derive(Debug, Clone, PartialEq, Eq)] + pub struct Value(Typed); + + 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_typed())?, + }; + Ok(Value(typed)) + } + pub(crate) fn to_expr(&self) -> NormalizedExpr { + self.0.normalize_to_expr() + } + pub(crate) fn as_typed(&self) -> &Typed { + &self.0 + } + + pub(crate) fn make_builtin_type(b: Builtin) -> Self { + Value(Typed::make_builtin_type(b)) + } + pub(crate) fn make_optional_type(t: Value) -> Self { + Value(Typed::make_optional_type(t.0)) + } + pub(crate) fn make_list_type(t: Value) -> Self { + Value(Typed::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(Typed::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(Typed::make_union_type( + kts.map(|(k, t)| (k, t.map(|t| t.0))), + )) + } + } + + 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()) + } + } + } + + /// 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. + // TODO: seal trait + pub trait Deserialize: 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()) + } +} |