jqish
| Crates.io | jqish |
| lib.rs | jqish |
| version | 0.1.1 |
| created_at | 2025-09-22 23:18:09.491131+00 |
| updated_at | 2025-09-23 03:26:07.433265+00 |
| description | A subset of the `jq` language for working with in-memory data structures |
| homepage | |
| repository | |
| max_upload_size | |
| id | 1850730 |
| size | 130,989 |
Lina Butler (linabutler)
documentation
README
jqish: A jq-like expression parser
jqish implements a subset of the jq language for querying and transforming JSON-like data.
While the venerable jq is a command-line tool that operates on JSON text, jqish is a library that operates on data structures in your program. Think of it like an alternative to JSONPath or JSON Pointer.
🚧 This project is still under development. There's a grammar and parser, but no evaluator yet.
Usage
Add jqish to your project's Cargo.toml:
[dependencies]
jqish = "0.1"
Quick Start
use jqish::{parse, Expr};
// Parse a simple object property access.
let expr = parse(".name").unwrap();
println!("{:?}", expr); // Expr::Index(...)
// Parse an expression that constructs an object.
let expr = parse("{name, age: .user.age, active}").unwrap();
println!("{:?}", expr); // Expr::Object([...])
// Parse a more complex expression.
let expr = parse("not (.foo | .bar // .baz)").unwrap();
println!("{:?}", expr); // Expr::Not(...)
Grammar comparison
✅ Supported
These features parse as described in the jq manual.
Filters
| Identity | . |
| Object identifier-indexing | .foo, .foo.bar, ."foo-bar" |
| Array and object indexing | .[0], .["key"], .[.expr] |
| Array slicing | .[1:3], .[2:], .[:5], .[:], .[-3], .[length() % 2] |
| Optionals | .foo?, ."foo-bar".baz?, .[1]? |
Types and values
| Numbers | 42, -10, 3.14, -1e10, 1.5e-3 |
| Strings | "hello", 'good-bye', "with \"escapes\"" |
| Literals | true, false, null |
| Array construction | [], [1, 2, 3], `[.a, .b, .c |
| Object construction | {}, {hello: "world"}, {name: .user, age, "favorite-name": .color}, {(.key): .value, (.prefix + .suffix): .result} |
Expressions and operators
| Pipes | `.a |
| Arithmetic operations | +, -, *, /, % |
| Comparisons | ==, !=, <, >, <=, >= |
| Boolean operators | a and b, a or b, not b |
| Alternatives | a // b |
| Grouping | (. + 2) * 5 |
❌ Not supported
Because jqish is designed to be embedded in a larger Rust program, it's missing some of jq's advanced features.
- Iterators and generators, including recursive descent:
.[],.foo[],.. | .a?. Since ajqishexpression can only return a single result, there's no way to represent the output of an iterator, generator, or recursive descent. - Control flow:
if-then-else,while,try-catch, and recursion. You can write more complex transformations that need these constructs in Rust. - Variables, including assignment operators:
... as $ident - Destructuring alternatives, because these require variables to work:
.[] as {$a, $b, c: {$d, $e}} ?// {$a, $b, c: [{$d, $e}]} | {$a, $b, $d, $e} - String interpolation:
"Hello \(name)" - Defining functions
- Modules
- Comments
License
jqish is distributed under the terms of either the MIT license or the Apache 2.0 license.
The jqish language is based on the syntax and semantics of jq, which is distributed under the MIT license.