jsonptr - JSON Pointers (RFC 6901) for Rust

JSON Pointers (RFC 6901) defines a string syntax for identifying a specific location within a JSON, or similar, document. This crate provides two types, Pointer and PointerBuf (akin to Path and PathBuf), for working with them abstractly.

A pointer is composed of zero or more Tokens, single segments which represent a field of an object or an index of an array, and are bounded by either '/' or the end of the string. Tokens are lightly encoded, where '~' is escaped as "~0" due to it signaling encoding and '/' is escaped as "~1" because '/' separates tokens and would split the token into two otherwise.

Tokens can be iterated over using either Tokens, returned from the tokens method of a pointer or Components, returned from the components method. The difference being that Tokens iterates over each token in the pointer, while Components iterates over Components, which can represent the root of the document or a single token of the pointer.

Operations resolve, assign and delete are provided as traits with corresponding methods on pointer types. Implementations of each trait are provided for value types of the crates serde_json and toml. All operations are enabled by default but are gated by feature flags.

Usage

Parsing and General Usage

To parse a Pointer from a string, use either Pointer::parse, for potentially fallible parsing, or the const fn from_static to produce a &'static Pointer from a string that is known to be valid.

use jsonptr::Pointer;

let ptr = Pointer::parse("/examples/0/name").unwrap();
let static_ptr = Pointer::from_static("/examples/0/name");
assert_eq!(ptr, static_ptr);

assert_eq!(ptr.get(1..).unwrap(), Pointer::parse("/0/name").unwrap());

let parent = ptr.parent().unwrap();
assert_eq!(parent, Pointer::parse("/examples/0").unwrap());

let (token, remaining) = ptr.split_front().unwrap();
assert_eq!(token.decoded(), "examples");
assert_eq!(remaining, Pointer::parse("/0/name").unwrap());

PointerBufs can be parsed using PointerBuf::parse or constructed from an iterator of Tokens with the from_tokens method:

use jsonptr::PointerBuf;
let mut buf = PointerBuf::parse("/examples/0/name").unwrap();

let from_tokens = PointerBuf::from_tokens(["examples", "0", "name"]);
assert_eq!(&buf, &from_tokens);

buf.push_front("pointer");
buf.push_front("~");
buf.push_back("/");
assert_eq!(buf.as_str(), "/~0/pointer/examples/0/name/~1");

Token Iteration

Iterating over the tokens or components of a pointer:

use jsonptr::{Pointer, Component, Token};
let ptr = Pointer::from_static("/path/to/value");

//  Using the `tokens` method:
let tokens: Vec<_> = ptr.tokens().collect();
assert_eq!(tokens, vec![Token::new("path"), Token::new("to"), Token::new("value")]);

// Using the `components` method:
let mut components = ptr.components();
assert_eq!(components.next(), Some(Component::Root));
assert_eq!(components.next(), Some(Component::Token(Token::new("path"))));
assert_eq!(components.next(), Some(Component::Token(Token::new("to"))));
assert_eq!(components.next(), Some(Component::Token(Token::new("value"))));

Resolving Values

To get a value at the location of a pointer, use either the Resolve and ResolveMut traits or Pointer::resolve and Pointer::resolve_mut methods. See the resolve mod for more information.

use jsonptr::Pointer;
use serde_json::json;

let ptr = Pointer::parse("/foo/bar").unwrap();
let data = json!({"foo": { "bar": 34 }});
let bar = ptr.resolve(&data).unwrap();
assert_eq!(bar, &json!(34));

Assigning Values

Values can be set, with path expansion, using the either the Assign trait or Pointer::assign. See assign for more information.

use jsonptr::Pointer;
use serde_json::json;

let ptr = Pointer::parse("/secret/universe").unwrap();
let mut data = json!({"secret": { "universe": 42 }});
let replaced = ptr.assign(&mut data, json!(34)).unwrap();
assert_eq!(replaced, Some(json!(42)));
assert_eq!(data, json!({"secret": { "universe": 34 }}));

Deleting Values

Values can be removed with the either the Delete trait or Pointer::delete. See delete for more information.

use jsonptr::Pointer;
use serde_json::json;

let ptr = Pointer::parse("/secret/universe").unwrap();
let mut data = json!({"secret": { "life": 42, "universe": 42, "everything": 42 }});
let deleted = ptr.delete(&mut data);
assert_eq!(deleted, Some(json!(42)));
assert_eq!(data, json!({"secret": { "life": 42, "everything": 42 }}));

Error Reporting

Any error produced by function calls into methods of traits or types of this crate can be converted into a [Report] which contains the original error and the [String] which failed to parse or the PointerBuf which failed to resolve or assign.

    use jsonptr::{Pointer, Diagnose};
    let ptr_str = "foo/bar";
    let err /* Result<&Pointer, Report<ParseError>> */ = Pointer::parse(ptr_str).diagnose(ptr_str).unwrap_err();
    assert!(err.original().is_no_leading_slash());

In the case of PointerBuf::parse, the [ParseError] is always wrapped in a [Report] so that the input String is not dropped.

    use jsonptr::{PointerBuf};
    let ptr_str = "foo/bar";
    let err /* Result<&PointerBuf, Report<ParseError>> */ = PointerBuf::parse(ptr_str).unwrap_err();
    assert!(err.original().is_no_leading_slash());

Feature Flags

Flag	Description	Enables	Default
"std"	Implements std::error::Error for error types		✓
"serde"	Enables serde support for types		✓
"json"	Implements ops for serde_json::Value	"serde"	✓
"toml"	Implements ops for toml::Value	"std", toml
"assign"	Enables the assign module and related pointer methods, providing a means to assign a value to a specific location within a document		✓
"resolve"	Enables the resolve module and related pointer methods, providing a means to resolve a value at a specific location within a document		✓
"delete"	Enables the delete module and related pointer methods, providing a means to delete a value at a specific location within a document	"resolve"	✓
"miette"	Enables integration with miette for error reporting	"std"

License

Licensed under either of

• Apache License, Version 2.0 (LICENSE-APACHE or http://www.apache.org/licenses/LICENSE-2.0)
• MIT license (LICENSE-MIT or http://opensource.org/licenses/MIT)

at your convenience.

Contribution

Contributions and feedback are always welcome and appreciated. If you find an issue, please open a ticket or a pull request.

Unless you explicitly state otherwise, any contribution intentionally submitted for inclusion in the work by you, as defined in the Apache-2.0 license, shall be dual licensed as above, without any additional terms or conditions.