jp — JSON Path Parser (Go)

A lightweight command-line tool written in Go that parses JSON files and extracts values using dot-notation paths.

This project is built as a learning exercise to deepen my understanding of Go, type handling, error design, and CLI tooling.

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🚧 Status

⚠️ This project is still under active development
Expect breaking changes, missing edge cases, and ongoing refactoring.

Current focus areas:

• API stabilization
• Performance improvements
• Expanded JSON path features
• Better CLI UX

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✨ Features

• Parse JSON files from disk
• Access nested values using dot notation
• Supports:
  • Objects
  • Arrays (by index)
  • Scalars (string, number, boolean, null)
• Custom error handling for:
  • Invalid keys
  • Array out-of-bounds access
• Pretty printing result with --pretty

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📦 Installation

Get the pkg

go get https://github.com/seggewiss/jp.git

🚀 Usage

jp [--pretty] <file> <dotNotationPath>

Example

Given data.json:

{
  "user": {
    "name": "John",
    "age": 30,
    "tags": ["dev", "go"]
  }
}

Run:

jp data.json user.name

Output:

{
  "user.name": "John"
}

Array access:

jp data.json user.tags.0

Output:

{
  "user.tags.0": "dev"
}

🧠 Why this project exists

This project is part of my effort to:

• Get my hands into Go again
• Build production-style project structure (cmd/, pkg/)
• Practice error handling patterns
• Work with encoding/json internals
• Improve testing discipline

⚠️ Limitations (current)

• No JSONPath support (only simple dot notation)
• No wildcards or filters
• No streaming for large JSON files
• Limited CLI features
• Error messages still evolving

🔮 Future improvements

• JSONPath-like expressions
• Performance optimizations for large files
• Optional JSON streaming decoder
• More expressive error reporting
• Benchmark suite

📌 Notes

This project is intentionally kept minimal and experimental. The goal is not just functionality, but understanding how Go handles real-world data traversal and tooling design.