JSON Parser

A high-performance, production-ready JSON parser written in Go with comprehensive error reporting and validation.

Features

• Fast JSON Parsing: Competitive performance with Go's standard library (within 17% for typical workloads)
• Enhanced Error Reporting: Detailed error messages with line/column positions, suggestions, and context
• Comprehensive Validation: Passes 20/20 official JSON test cases, correctly rejects 20/23 invalid cases
• Full JSON Support: Objects, arrays, strings, numbers, booleans, null, nested structures
• Unicode Support: Full UTF-8 and escape sequence handling including \uXXXX
• Production Ready: Extensive test coverage, benchmarked, and stress-tested

Installation

go build -o json-parser ./cmd/json-parser

Usage

Command Line

# Parse and validate a JSON file
./json-parser example.json

# Exit codes:
# 0 = Valid JSON
# 1 = Invalid JSON or file error

As a Library

import (
    "github.com/VuNe/json-parser/internal/lexer"
    "github.com/VuNe/json-parser/internal/parser"
)

// Basic parsing
input := `{"name": "John", "age": 30}`
l := lexer.New(input)
p := parser.New(l)
result, err := p.Parse()

// Enhanced error reporting  
p := parser.NewWithInput(l, input)
result, err := p.Parse()
if err != nil {
    fmt.Printf("Parse error: %v\n", err) // Includes line/column info and suggestions
}

Architecture

The parser follows a clean 3-layer architecture:

1. Lexer: Tokenizes raw JSON input with position tracking
2. Parser: Recursive descent parser that builds structured data
3. CLI: Command-line interface with file I/O and exit code management

Performance

Benchmarked against Go's standard library:

• Speed: ~3961 ns/op (vs stdlib 3372 ns/op) - 17% slower
• Memory: 768 B/op (vs stdlib 640 B/op) - 20% more memory
• Error Detection: Very fast at 1100-2300 ns/op

The slight overhead provides significantly better error messages and diagnostic information.

Error Handling

Enhanced error messages include:

Syntax error at line 2, column 15: missing colon after object key
Expected ':', but found '"'
Near: 2| "key" "value"
                ^
Suggestion: Add a ':' after the object key

Supported JSON Features

• ✅ Objects with string keys
• ✅ Arrays with mixed types
• ✅ Strings with escape sequences (\", \\, \n, \t, \r, \b, \f, \/)
• ✅ Unicode escapes (\uXXXX)
• ✅ Numbers (integers, floats, scientific notation)
• ✅ Booleans (true, false)
• ✅ Null values
• ✅ Nested structures (objects and arrays)
• ✅ Whitespace handling
• ❌ Comments (not part of JSON spec)
• ❌ Trailing commas (not part of JSON spec)
• ❌ Single quotes (not part of JSON spec)

Testing

Comprehensive test suite includes:

• Unit tests for all components (75%+ coverage)
• Official JSON test suite (43 test cases)
• Performance benchmarks
• Integration tests
• Edge case and stress testing

# Run all tests
make test

# Run benchmarks
go test ./internal/parser -bench=. -benchmem

# Run with coverage
go test -cover ./...

Development

Building

make help          # Show available commands
make test          # Run test suite
make clean         # Clean build artifacts

Project Structure

├── cmd/json-parser/       # CLI application
├── internal/
│   ├── lexer/            # Tokenization
│   ├── parser/           # JSON grammar parsing  
│   └── cli/              # CLI interface
├── test/                 # Test files and data
└── docs/                 # Documentation

License

This project is part of a JSON parser implementation challenge.