GBNF-rs

A library for working with llama.cpp GBNF files. This project is meant to help make it easier to constrain and guide GBNF driven AIs like llama.cpp.

Data structures for representing GBNF
Rendering of a GBNF file from data structures
Conversion of a useful subset of JSON schema to GBNF grammar
MIT licensed

This library was primarily built for it's sister project, an LLM API epistemology.

Installing

cargo add gnbf

JSON schema support

Currently this library can convert a limited but very useful subset of JSON schema:

boolean, number, string
object with all required properties
enum
oneOf
property order of objects is preserved

Known issues:

objects with property names with underscores don't translate well right now

Here's one of the most complext JSON schemas that can be handled right now:

{
    "$schema": "https://json-schema.org/draft/2019-09/schema",
    "type": "object",
    "properties": {
        "name": {
            "description": "name of a computer user",
            "type": "string"
        },
        "age": {
            "description": "age of a computer user",
            "type": "number"
        },
        "usesAI": {
            "description": "do they use AI",
            "type": "boolean"
        },
        "favoriteAnimal": {
            "description": "favorite animal",
            "enum": [
                "dog",
                "cat",
                "none"
            ]
        },
        "currentAIModel": {
            "oneOf": [
                {
                    "type": "object",
                    "properties": {
                        "type": {
                            "value": "hugging_face"
                        },
                        "name": {
                            "description": "name of hugging face model",
                            "type": "string"
                        }
                    }
                },
                {
                    "type": "object",
                    "properties": {
                        "type": {
                            "value": "openai"
                        }
                    }
                }
            ]
        }
    }
}

JSON-Schema Converting to AI Grammar

fn simple_json_schema_basic_object_example() {
        let schema = r#"
    {
        "$id": "https://example.com/enumerated-values.schema.json",
        "$schema": "https://json-schema.org/draft/2020-12/schema",
        "title": "Enumerated Values",
        "type": "object",
        "properties": {
            "a": {
                "type": "boolean"
            },
            "b": {
                "type": "number"
            },
            "c": {
                "type": "string"
            }
        }
    }
            "#;
        let g = Grammar::from_json_schema(schema).unwrap();
        let s = g.to_string();
        pretty_assertions::assert_eq!(
            s,
            r#"################################################
# DYNAMICALLY GENERATED JSON-SCHEMA GRAMMAR
# $id: https://example.com/enumerated-values.schema.json
# $schema: https://json-schema.org/draft/2020-12/schema
# title: Enumerated Values
################################################

symbol1-a-value ::= boolean ws
symbol2-b-value ::= number ws
symbol3-c-value ::= string ws
root ::= "{" ws 
 "a" ws ":" ws symbol1-a-value 
 "b" ws ":" ws symbol2-b-value "," ws 
 "c" ws ":" ws symbol3-c-value "," ws 
 "}" ws

###############################
# Primitive value type symbols
###############################
null ::= "null" ws
boolean ::= "true" | "false" ws
string ::= "\"" ([^"\\] | "\\" (["\\/bfnrt] | "u" [0-9a-fA-F] [0-9a-fA-F] [0-9a-fA-F] [0-9a-fA-F]))* "\"" ws
number ::= ("-"? ([0-9] | [1-9] [0-9]*)) ("." [0-9]+)? ([eE] [-+]? [0-9]+)? ws
ws ::= [ ]
"#
        )
    }

Future goals of this project:

offer standard grammars
handle useful conversion of JSON schema to GBNF (we won't be able to handle it all probably).
parsing of GBNF files using Nom 7.

I'm totally down for contributors, please add tests.

See the documentation.

Attribution