JSON Predicate

Partial implementation of Snell Json Predicate Draft 07.

Even if this Draft is Expired, it's still a pretty good draft of predicate over JSON.

Introduction

This specification defines JSON Predicates, a JSON-based RFC4627 syntax for the description and serialization of logical boolean predicate operations intended to be used in conjunction with other JSON-based mechanisms, such as JSON Patch RFC6902, as a means of incorporating conditional processing.

JSON Predicates can be used, for instance, to extend a JSON Patch RFC6902 document to provide for a broader range of conditional processing options not currently supported by JSON Patch.

Example

Given this JSON:

{
    "a": {
        "b": {
            "c": "ABC!XYZ"
        }
    }
}

We could have a predicate like this:

{
    "op": "and",
    "path": "/a/b/c",
    "apply": [
        {
            "op": "type",
            "value": "string"
        },
        {
            "op": "contains",
            "value": "ABC"
        }
    ]
}

which would evaluate as true if evaluated against the previous JSON.

Rust Example

let predicate = Predicate::deserialize(serde_json::json!({
    "op": "and",
    "path": "/objA",
    "apply": [
      {
        "op": "defined",
        "path": "/stringX"
      },
      {
        "op": "defined",
        "path": "/stringXYZ"
      }
    ],
}))?;

let evaluted_predicate: bool = predicate
    .test(&ENTRY, PredicateContext::default());

JSON Patch

The JSON Patch methods described in draft-snell-json-test-07 are not implemented yet.

Features

First order predicate

• "contains"
• "contains-"
• "defined"
• "undefined"
• "starts"
• "starts-"
• "ends"
• "ends-"
• "type"
• "in"
• "in-"
• "matches"
• "matches-"
• "test"
• "test-"
• "less"
• "more"

Second order predicate

• "and"
• "not"
• "or"

References

• Specification draft-snell-json-test-07

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 option.