summaryrefslogtreecommitdiff
path: root/serde_dhall/src/lib.rs
blob: d8a093caf87d13211b849fe7ce76cd741c061804 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
#![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};