JsonPath for Elixir

[!WARNING] This Package is EXPERIMENTAL and in development. It may not be suitable for production use.

A minimal JSONPath engine in Elixir using LEEX + YECC generated modules.

This library supports querying nested maps and lists using JSONPath syntax. It currently implements a partial subset of RFC 9535 and passes 400/702 compliance tests.

Features

• Child selector (.) and descendant selector (..)
• Wildcards (*) for maps and arrays
• Array slices and indices ([0:2], [-1])
• Unions ([0,2])
• Basic filters ([?@.price<20])
• Returns paths and values in evaluation
• Convenience query/2 helper for automatic tokenize → parse → evaluate
• Works with Elixir maps and lists

⚠️ Partial implementation: not all RFC 9535 features are implemented yet.

Installation

Add to your mix.exs:

def deps do
  [
    {:json_path, "~> 0.1.0"}
  ]
end

Then fetch dependencies:

mix deps.get

Usage

Basic Queries

data = %{
  "store" => %{
    "book" => [
      %{"title" => "Elixir in Action", "price" => 15},
      %{"title" => "Programming Phoenix", "price" => 20}
    ],
    "bicycle" => %{"color" => "red", "price" => 100}
  }
}

# Get all book prices
JsonPath.query(data, "$.store.book[*].price")
# => [{"$['store']['book'][0]['price']", 15}, {"$['store']['book'][1]['price']", 20}]

# Get bicycle color
JsonPath.query(data, "$.store.bicycle.color")
# => [{"$['store']['bicycle']['color']", "red"}]

Advanced Queries

# Descendant selector
JsonPath.query(data, "$..price")
# => [{"$['store']['book'][0]['price']", 15}, {"$['store']['book'][1]['price']", 20}, {"$['store']['bicycle']['price']", 100}]

# Union selection
JsonPath.query(data, "$.store.book[0,1]")
# => [{"$['store']['book'][0]", ...}, {"$['store']['book'][1]", ...}]

# Array slice
JsonPath.query(data, "$.store.book[0:2]")
# => first two books

# Negative index
JsonPath.query(data, "$.store.book[-1]")
# => last book

# Filter with comparison
JsonPath.query(data, "$..book[?@.price<20]")
# => books with price < 20

# Logical filter (AND/OR)
JsonPath.query(data, "$..book[?@.price>10 && @.price<30]")
# => books with 10 < price < 30

Functions

JsonPath.query(data, path_string)

Convenience function to tokenize → parse → evaluate in one call.

• Parameters:
  • data – Map or List to query
  • path_string – JSONPath string
• Returns:
  • List of {path_string, value} or {:error, reason}

JsonPath.tokenize(query)

Tokenizes a JSONPath string using the lexer.

• Returns:{:ok, tokens, line} or {:error, reason}

JsonPath.parse(tokens)

Parses a token list into an AST.

• Returns:{:ok, ast} or {:error, reason}

JsonPath.evaluate(ast, data)

Evaluates a parsed AST against data.

• Returns: List of {path_string, value}

Compliance & Coverage

• Partial RFC 9535 implementation
• Passing 400/702 JSONPath compliance tests (link)
• Work in progress for full RFC coverage

Contributing

1. Fork the repository
2. Implement or improve features
3. Run tests: mix test
4. Submit a pull request

License

Apache License 2.0 © Jacob Aronoff