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+#![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())
+ }
+}