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 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215
//! [balena] **tem**plating **en**gine //! //! A crate that provides facilities to: //! //! * parse an expression //! * evaluate an expression //! * evaluate an expression as a boolean (logical expressions) //! * register custom functions and filters //! //! [Expression language documentation]. //! //! # Versioning //! //! This crate is being actively developed and it does NOT follow [Semantic Versioning] yet. //! It will follow semantic versioning when it reaches version 1.0. //! //! MINOR version changes denotes incompatible API changes and PATCH version changes denotes //! both new functionality in a backwards-compatible manner and backwards-compatible bug fixes. //! //! # Examples //! //! ## Helpers //! //! ### JSON evaluation //! //! ```rust //! use balena_temen::{evaluate, Value}; //! use serde_json::json; //! //! let data = json!({ //! "wifi": { //! "ssid": "Balena Ltd", //! "id": { //! "$$formula": "super.ssid | SLUGIFY" //! } //! } //! }); //! let evaluated = json!({ //! "wifi": { //! "ssid": "Balena Ltd", //! "id": "balena-ltd" //! } //! }); //! assert_eq!(evaluate(data).unwrap(), evaluated); //! ``` //! //! ### JSON with custom evaluation keyword //! //! ```rust //! use balena_temen::{Context, Engine, EngineBuilder, evaluate_with_engine, Value}; //! use serde_json::json; //! //! let data = json!({ //! "evalMePlease": "3 + 5 * 2" //! }); //! let evaluated = json!(13); //! //! let mut ctx = Context::default(); //! let engine: Engine = EngineBuilder::default() //! .eval_keyword("evalMePlease") //! .into(); //! //! assert_eq!(evaluate_with_engine(data, &engine, &mut ctx).unwrap(), evaluated); //! ``` //! //! ## Intermediate //! //! ### Single expression evaluation //! //! ```rust //! use balena_temen::{ //! ast::Identifier, //! Engine, Context, Value //! }; //! use serde_json::json; //! //! let engine = Engine::default(); // Default functions, filters //! let mut ctx = Context::default(); // Default context //! let position = Identifier::default(); // Evaluate from the root //! let data = Value::Null; //! //! assert_eq!( //! engine.eval("2 + 3", &position, &data, &mut ctx).unwrap(), //! json!(5) //! ); //! //! assert_eq!( //! engine.eval("`Balena templating engine!` | SLUGIFY", &position, &data, &mut ctx).unwrap(), //! json!("balena-templating-engine") //! ); //! ``` //! //! ### Single logical expression evaluation //! //! ```rust //! use balena_temen::{ //! ast::Identifier, //! Engine, Context, Value //! }; //! use serde_json::json; //! //! let engine = Engine::default(); // Default functions, filters //! let mut ctx = Context::default(); // Default context //! let position = Identifier::default(); // Evaluate from the root //! let data = Value::Null; //! //! assert_eq!( //! engine.eval_as_bool("1 == 1", &position, &data, &mut ctx).unwrap(), //! json!(true) //! ); //! //! assert_eq!( //! engine.eval_as_bool("2 > 4", &position, &data, &mut ctx).unwrap(), //! json!(false) //! ); //! //! assert_eq!( //! engine.eval_as_bool("1 > 4 or 3 > 2", &position, &data, &mut ctx).unwrap(), //! json!(true) //! ); //! ``` //! //! ## Advanced //! //! ### Custom functions and filters //! //! Visit [`EngineBuilder::function`] and [`EngineBuilder::filter`] methods //! documentation for examples. //! //! ### Expression parsing //! //! ```rust //! use balena_temen::ast::*; //! //! // Parse expression automatically //! let parsed: Expression = "1 + 2 == 3".parse().unwrap(); //! //! // Construct expression manually //! let lhs = Expression::new( //! ExpressionValue::Math( //! MathExpression::new( //! Expression::new(ExpressionValue::Integer(1)), //! Expression::new(ExpressionValue::Integer(2)), //! MathOperator::Addition //! ) //! ) //! ); //! let rhs = Expression::new( //! ExpressionValue::Integer(3) //! ); //! let full_expression = Expression::new( //! ExpressionValue::Logical( //! LogicalExpression::new( //! lhs, rhs, LogicalOperator::Equal //! ) //! ) //! ); //! //! // Compare and check that the expression was parsed correctly //! assert_eq!(parsed, full_expression); //! ``` //! //! Visit [ast] module documentation for more info. //! //! ### Identifier parsing //! //! ```rust //! use balena_temen::ast::*; //! //! let s = "wifi.networks[0].ssid"; //! //! // Parse it //! let parsed: Identifier = s.parse().unwrap(); //! //! // Create manually //! let manual = Identifier::default() //! .name("wifi") //! .name("networks") //! .index(0) //! .name("ssid"); //! //! assert_eq!(parsed, manual); //! ``` //! //! [balena]: https://www.balena.io //! [ast]: ast/index.html //! [`EngineBuilder::function`]: struct.EngineBuilder.html#method.function //! [`EngineBuilder::filter`]: struct.EngineBuilder.html#method.filter //! [Semantic Versioning]: https://semver.org/ //! [Expression language documentation]: https://github.com/balena-io-modules/balena-temen/blob/master/docs/expression.md #![allow(clippy::possible_missing_comma)] pub use serde_json::Value; pub use crate::{ builtin::{filter::FilterFn, function::FunctionFn}, context::Context, engine::{ builder::EngineBuilder, helper::{evaluate, evaluate_with_engine}, Engine, }, }; #[allow(deprecated)] pub use crate::engine::helper::{eval, eval_with_engine}; pub(crate) mod builtin; pub mod ast; mod context; mod engine; pub mod error; mod parser; mod utils;