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//! ## Overview //! //! > Prior to v0.4.0 this crate was named [json-query]. //! //! This rust crate provides access to [jq] 1.6 via the `libjq` C API (rather than //! "shelling out"). //! //! By leveraging [jq] we can extract data from json strings using `jq`'s dsl. //! //! This crate requires Rust **1.32** or above. //! //! ## Usage //! //! The interface provided by this crate is very basic. You supply a jq program //! string and a string to run the program over. //! //! ```rust //! use jq_rs; //! // ... //! //! let res = jq_rs::run(".name", r#"{"name": "test"}"#); //! assert_eq!(res.unwrap(), "\"test\"\n".to_string()); //! ``` //! //! In addition to running one-off programs with `jq_rs::run()`, you can also //! use `jq_rs::compile()` to compile a jq program and reuse it with //! different inputs. //! //! ```rust //! use jq_rs; //! //! let tv_shows = r#"[ //! {"title": "Twilight Zone"}, //! {"title": "X-Files"}, //! {"title": "The Outer Limits"} //! ]"#; //! //! let movies = r#"[ //! {"title": "The Omen"}, //! {"title": "Amityville Horror"}, //! {"title": "The Thing"} //! ]"#; //! //! let mut program = jq_rs::compile("[.[].title] | sort").unwrap(); //! //! assert_eq!( //! &program.run(tv_shows).unwrap(), //! "[\"The Outer Limits\",\"Twilight Zone\",\"X-Files\"]\n" //! ); //! //! assert_eq!( //! &program.run(movies).unwrap(), //! "[\"Amityville Horror\",\"The Omen\",\"The Thing\"]\n", //! ); //! ``` //! //! ## A Note on Performance //! //! While the benchmarks are far from exhaustive, they indicate that much of the //! runtime of a simple jq program goes to the compilation. In fact, the compilation //! is _quite expensive_. //! //! ```text //! run one off time: [48.594 ms 48.689 ms 48.800 ms] //! Found 6 outliers among 100 measurements (6.00%) //! 3 (3.00%) high mild //! 3 (3.00%) high severe //! //! run pre-compiled time: [4.0351 us 4.0708 us 4.1223 us] //! Found 15 outliers among 100 measurements (15.00%) //! 6 (6.00%) high mild //! 9 (9.00%) high severe //! ``` //! //! If you have a need to run the same jq program multiple times it is //! _highly recommended_ to retain a pre-compiled `JqProgram` and reuse it. //! //! ## Handling Output //! //! The return values from jq are _strings_ since there is no certainty that the //! output will be valid json. As such the output will need to be parsed if you want //! to work with the actual data types being represented. //! //! In such cases you may want to pair this crate with [serde_json] or similar. //! //! For example, here we want to extract the numbers from a set of objects: //! //! ```rust //! use jq_rs; //! use serde_json::{self, json}; //! //! // ... //! //! let data = json!({ //! "movies": [ //! { "title": "Coraline", "year": 2009 }, //! { "title": "ParaNorman", "year": 2012 }, //! { "title": "Boxtrolls", "year": 2014 }, //! { "title": "Kubo and the Two Strings", "year": 2016 }, //! { "title": "Missing Link", "year": 2019 } //! ] //! }); //! //! let query = "[.movies[].year]"; //! // program output as a json string... //! let output = jq_rs::run(query, &data.to_string()).unwrap(); //! // ... parse via serde //! let parsed: Vec<i64> = serde_json::from_str(&output).unwrap(); //! //! assert_eq!(vec![2009, 2012, 2014, 2016, 2019], parsed); //! ``` //! //! Barely any of the options or flags available from the [jq] cli are exposed //! currently. //! Literally all that is provided is the ability to execute a _jq program_ on a blob //! of json. //! Please pardon my dust as I sort out the details. //! //! ## Linking to libjq //! //! This crate requires access to `libjq` at build and/or runtime depending on the //! your choice. //! //! When the `bundled` feature is enabled (**off by default**) `libjq` is provided //! and linked statically to your crate by [jq-sys] and [jq-src]. Using this feature //! requires having autotools and gcc in `PATH` in order for the to build to work. //! //! Without the `bundled` feature, _you_ will need to ensure your crate //! can link to `libjq` in order for the bindings to work. //! //! You can choose to compile `libjq` yourself, or perhaps install it via your //! system's package manager. //! See the [jq-sys building docs][jq-sys-building] for details on how to share //! hints with the [jq-sys] crate on how to link. //! //! [jq]: https://github.com/stedolan/jq //! [serde_json]: https://github.com/serde-rs/json //! [jq-rs]: https://crates.io/crates/jq-rs //! [json-query]: https://crates.io/crates/json-query //! [jq-sys]: https://github.com/onelson/jq-sys //! [jq-sys-building]: https://github.com/onelson/jq-sys#building //! [jq-src]: https://github.com/onelson/jq-src #![deny(missing_docs)] extern crate jq_sys; #[cfg(test)] #[macro_use] extern crate serde_json; mod errors; mod jq; use std::ffi::CString; pub use errors::{Error, Result}; /// Run a jq program on a blob of json data. /// /// In the case of failure to run the program, feedback from the jq api will be /// available in the supplied `String` value. /// Failures can occur for a variety of reasons, but mostly you'll see them as /// a result of bad jq program syntax, or invalid json data. pub fn run(program: &str, data: &str) -> Result<String> { compile(program)?.run(data) } /// A pre-compiled jq program which can be run against different inputs. pub struct JqProgram { jq: jq::Jq, } impl JqProgram { /// Runs a json string input against a pre-compiled jq program. pub fn run(&mut self, data: &str) -> Result<String> { if data.trim().is_empty() { // During work on #4, #7, the parser test which allows us to avoid a memory // error shows that an empty input just yields an empty response BUT our // implementation would yield a parse error. return Ok("".into()); } let input = CString::new(data)?; self.jq.execute(input) } } /// Compile a jq program then reuse it, running several inputs against it. pub fn compile(program: &str) -> Result<JqProgram> { let prog = CString::new(program)?; Ok(JqProgram { jq: jq::Jq::compile_program(prog)?, }) } #[cfg(test)] mod test { use super::{compile, run, Error}; use matches::assert_matches; use serde_json; #[test] fn reuse_compiled_program() { let query = r#"if . == 0 then "zero" elif . == 1 then "one" else "many" end"#; let mut prog = compile(&query).unwrap(); assert_eq!(prog.run("2").unwrap(), "\"many\"\n"); assert_eq!(prog.run("1").unwrap(), "\"one\"\n"); assert_eq!(prog.run("0").unwrap(), "\"zero\"\n"); } #[test] fn jq_state_is_not_global() { let input = r#"{"id": 123, "name": "foo"}"#; let query1 = r#".name"#; let query2 = r#".id"#; // Basically this test is just to check that the state pointers returned by // `jq::init()` are completely independent and don't share any global state. let mut prog1 = compile(&query1).unwrap(); let mut prog2 = compile(&query2).unwrap(); assert_eq!(prog1.run(input).unwrap(), "\"foo\"\n"); assert_eq!(prog2.run(input).unwrap(), "123\n"); assert_eq!(prog1.run(input).unwrap(), "\"foo\"\n"); assert_eq!(prog2.run(input).unwrap(), "123\n"); } fn get_movies() -> serde_json::Value { json!({ "movies": [ { "title": "Coraline", "year": 2009 }, { "title": "ParaNorman", "year": 2012 }, { "title": "Boxtrolls", "year": 2014 }, { "title": "Kubo and the Two Strings", "year": 2016 }, { "title": "Missing Link", "year": 2019 } ] }) } #[test] fn identity_nothing() { assert_eq!(run(".", "").unwrap(), "".to_string()); } #[test] fn identity_empty() { assert_eq!(run(".", "{}").unwrap(), "{}\n".to_string()); } #[test] fn extract_dates() { let data = get_movies(); let query = "[.movies[].year]"; let output = run(query, &data.to_string()).unwrap(); let parsed: Vec<i64> = serde_json::from_str(&output).unwrap(); assert_eq!(vec![2009, 2012, 2014, 2016, 2019], parsed); } #[test] fn extract_name() { let res = run(".name", r#"{"name": "test"}"#); assert_eq!(res.unwrap(), "\"test\"\n".to_string()); } #[test] fn unpack_array() { let res = run(".[]", "[1,2,3]"); assert_eq!(res.unwrap(), "1\n2\n3\n".to_string()); } #[test] fn compile_error() { let res = run(". aa12312me dsaafsdfsd", "{\"name\": \"test\"}"); assert_matches!(res, Err(Error::InvalidProgram)); } #[test] fn parse_error() { let res = run(".", "{1233 invalid json ahoy : est\"}"); assert_matches!(res, Err(Error::System { .. })); } #[test] fn just_open_brace() { let res = run(".", "{"); assert_matches!(res, Err(Error::System { .. })); } #[test] fn just_close_brace() { let res = run(".", "}"); assert_matches!(res, Err(Error::System { .. })); } #[test] fn total_garbage() { let data = r#" { moreLike: "an object literal but also bad" loveToDangleComma: true, }"#; let res = run(".", data); assert_matches!(res, Err(Error::System { .. })); } pub mod mem_errors { //! Attempting run a program resulting in bad field access has been //! shown to sometimes trigger a use after free or double free memory //! error. //! //! Technically the program and inputs are both valid, but the //! evaluation of the program causes bad memory access to happen. //! //! https://github.com/onelson/json-query/issues/4 use super::*; #[test] fn missing_field_access() { let prog = ".[] | .hello"; let data = "[1,2,3]"; let res = run(prog, data); assert_matches!(res, Err(Error::System { .. })); } #[test] fn missing_field_access_compiled() { let mut prog = compile(".[] | .hello").unwrap(); let data = "[1,2,3]"; let res = prog.run(data); assert_matches!(res, Err(Error::System { .. })); } } }