Go JSON Parser

A lightweight JSON parser written in Go that supports JSON formatting and selective querying using dot notation. This parser implements a custom lexer and parser to handle JSON data structures.

Features

• Custom lexer and parser implementation
• JSON string formatting with customizable indentation
• Query JSON data using dot notation path selectors
• Support for all JSON data types:
  • Objects
  • Arrays
  • Strings
  • Numbers
  • Booleans
  • Null

Installation

git clone https://github.com/Prashant047/go-json.git
cd go-json
go build

Usage

The parser supports two main operations: format and select.

Formatting JSON

Format JSON with custom indentation:

# Format JSON from a file
go-json format -f input.json -t "    "

# Format JSON from stdin
echo '{"name": "John", "age": 30}' | go-json format

Querying JSON

Select specific values using dot notation:

# Query from a file
go-json select -q "user.address.street" -f input.json

# Query from stdin
echo '{"user": {"address": {"street": "123 Main St"}}}' | go-json select -q "user.address.street"

Query Syntax

• Use dot notation to access object properties: user.name
• Use bracket notation with indices to access array elements: users.[0].name
• Combine both for complex queries: users.[0].addresses.[1].street

Examples

Given this JSON:

{
    "users": [
        {
            "name": "John",
            "age": 30,
            "addresses": [
                {
                    "type": "home",
                    "street": "123 Main St"
                },
                {
                    "type": "work",
                    "street": "456 Market St"
                }
            ]
        }
    ]
}

Query examples:

# Get the first user's name
go-json select -q "users.[0].name" -f user.json
# Output: "John"

# Get the first user's work address
go-json select -q "users.[0].addresses.[1]" -f user.json
# Output: {
#     "type": "work",
#     "street": "456 Market St"
# }

Implementation Details

The parser is implemented in several components:

• lexer: Tokenizes JSON input into a stream of tokens
• parser: Constructs an AST (Abstract Syntax Tree) from tokens
• ast: Defines the node types for the syntax tree
• operations: Implements formatting and query operations