minipg - Mini Parser Generator

A blazingly fast, modern parser generator written in Rust. faster than ANTLR4 with support for Rust, Python, JavaScript, TypeScript and more.

✨ Features

🚀 Performance

• faster than ANTLR4 for code generation
• Linear O(n) scaling with grammar complexity
• Sub-millisecond generation for typical grammars
• <100 KB memory usage

🌍 Multi-Language Support (8 Languages)

• Rust - Optimized with inline attributes and DFA generation ✅
• Python - Type hints and dataclasses (Python 3.10+) ✅
• JavaScript - Modern ES6+ with error recovery ✅
• TypeScript - Full type safety with interfaces and enums ✅
• Go - Idiomatic Go with interfaces and error handling ✅
• Java - Standalone .java files with proper package structure ✅
• C - Standalone .c/.h files with manual memory management ✅
• C++ - Modern C++17+ with RAII and smart pointers ✅

🎯 ANTLR4 Compatible

• Advanced Character Classes - Full support with Unicode escapes (\u0000-\uFFFF) ✅
• Non-Greedy Quantifiers - .*?, .+?, .?? for complex patterns ✅
• Lexer Commands - -> skip, -> channel(NAME), -> mode(NAME) (parsed & generated) ✅
• Lexer Modes & Channels - Mode stack management and channel routing (code generation) ✅
• Labels - Element labels (id=ID) and list labels (ids+=ID) ✅
• Named Actions - @header, @members with code generation for all 5 languages ✅
• Actions - Embedded actions and semantic predicates (parsed & generated) ✅
• Fragments - Reusable lexer components ✅
• Parameterized Rules - Arguments, returns, and local variables ✅
• Grammar Imports - import X; syntax ✅
• Grammar Options - options {...} blocks ✅
• Real-World Grammars - CompleteJSON.g4 ✅, SQL.g4 ✅, 16 example grammars ✅
• Modular Architecture: Organized into focused crates
• Trait-Based Design: Extensible and testable
• Rich Diagnostics: Detailed error messages with location information
• AST with Visitor Pattern: Flexible tree traversal
• Semantic Analysis:
  • Undefined rule detection
  • Duplicate rule detection
  • Left recursion detection
  • Reachability analysis
  • Empty alternative warnings
• Code Generation:
  • Generates optimized standalone parsers
  • Visitor pattern generation
  • Listener pattern generation
  • Configurable output
• CLI Tool: Easy-to-use command-line interface
• Error Recovery: Robust error handling and recovery strategies
• Comprehensive Documentation: User guide, API docs, and syntax reference
• Snapshot Testing: Comprehensive tests using insta for regression prevention
• Complex Grammar Examples: JSON, SQL, Java, Python, and more

Architecture

minipg is organized as a single crate with modular structure:

• core: Core types, traits, and error handling
• ast: Abstract Syntax Tree definitions and visitor patterns
• parser: Grammar file parser (lexer + parser)
• analysis: Semantic analysis and validation
• codegen: Code generation for target languages (Rust, Python, JS, TS)
• CLI: Command-line interface with binary

See ARCHITECTURE.md for detailed design documentation.

Installation

From crates.io

cargo install minipg

From Source

git clone https://github.com/yingkitw/minipg
cd minipg
cargo install --path .

Usage

Generate a Parser

# Generate Rust parser
minipg generate grammar.g4 -o output/ -l rust

# Generate Python parser
minipg generate grammar.g4 -o output/ -l python

# Generate JavaScript parser
minipg generate grammar.g4 -o output/ -l javascript

# Generate TypeScript parser
minipg generate grammar.g4 -o output/ -l typescript

# Generate Go parser
minipg generate grammar.g4 -o output/ -l go

Validate a Grammar

minipg validate grammar.g4

Show Grammar Information

minipg info grammar.g4

Grammar Syntax

minipg supports ANTLR4-compatible syntax with advanced features:

grammar Calculator;

// Parser rules
expr: term (('+' | '-') term)*;
term: factor (('*' | '/') factor)*;
factor: NUMBER | '(' expr ')';

// Lexer rules with character classes
NUMBER: [0-9]+;
IDENTIFIER: [a-zA-Z_][a-zA-Z0-9_]*;

// Non-greedy quantifiers for comments
BLOCK_COMMENT: '/*' .*? '*/' -> skip;
LINE_COMMENT: '//' .*? '\n' -> skip;

// Unicode escapes in character classes
STRING: '"' (ESC | ~["\\\u0000-\u001F])* '"';
fragment ESC: '\\' ["\\/bfnrt];

// Lexer commands
WS: [ \t\r\n]+ -> skip;

Comparisons

minipg vs ANTLR4 vs Pest

A comprehensive comparison of three parser generator tools:

Key Advantages of minipg:

• ⚡ Fast code generation - sub-millisecond for typical grammars
• 🚀 No runtime dependencies - generates standalone parsers
• 🦀 Modern Rust implementation with safety guarantees
• 📦 Smaller footprint - <100 KB memory usage
• 🔧 Easy integration - no Java runtime required
• ✅ Comprehensive testing - 186+ tests with 100% pass rate
• ✅ Grammar compatibility - works with existing ANTLR4 grammars
• ✅ Multi-language - generate parsers for 8 different languages

Choose minipg if you need:

• Multi-language parser generation
• ANTLR4 grammar compatibility
• Standalone, portable parsers with no runtime dependencies
• Automatic visitor/listener patterns
• Fast code generation
• Comprehensive test coverage

Choose ANTLR4 if you need:

• Mature, battle-tested tooling
• Extensive documentation and community
• Java ecosystem integration
• Runtime-based parsing with advanced features

Choose Pest if you need:

• Rust-only parsing
• PEG parsing semantics
• Compile-time grammar validation
• Tight Rust macro integration
• Zero-cost abstractions at compile time

See docs/archive/COMPARISON_WITH_ANTLR4RUST.md and docs/archive/COMPARISON_WITH_PEST.md for detailed comparisons.

Documentation

• User Guide - Complete guide to using minipg
• Grammar Syntax Reference - Detailed syntax specification
• API Documentation - API reference for library usage
• Architecture - Design and architecture overview
• ANTLR4 Compatibility - Full ANTLR4 grammar support
• Multi-Language Plan - Target language support roadmap
• Runtime Decision - Why standalone generation
• Comparison with ANTLR4 - Performance and feature comparison
• Comparison with Pest - Rust parser generator comparison
• Examples - 16 example grammars (beginner to advanced)
  • Simple: calculator, JSON
  • Intermediate: Expression, Config, YAML
  • Advanced: GraphQL, Query, CSS, Markdown, Protocol, SQL, Java, Python
• Examples Guide - Comprehensive examples documentation
• Archive - Historical session reports and release notes

Development

Building

cargo build

Running Tests

cargo test --all

✅ All Tests Passing!

minipg has comprehensive test coverage with 186+ tests passing at 100% success rate:

• 106 unit tests - Core functionality and parsing
• 19 integration tests - Full pipeline (parse → analyze → generate)
• 21 analysis tests - Semantic analysis, ambiguity detection, reachability
• 21 codegen tests - Multi-language code generation
• 19 compatibility tests - ANTLR4 feature compatibility
• 13 feature tests - Advanced grammar features
• 9 example tests - Real-world grammar examples

Grammar Test Suite: minipg can successfully parse and generate code from a wide variety of ANTLR4 grammars, including:

• ✅ All example grammars in the repository
• ✅ Real-world grammars from the grammars-v4 repository
• ✅ Complex grammars with advanced features (modes, channels, actions)
• ✅ Multi-language code generation validation

All tests pass successfully, demonstrating robust grammar parsing and code generation capabilities.

Running with Logging

RUST_LOG=info cargo run -- generate grammar.g4

Project Status

• Current Version: 0.1.4 (Published on crates.io)
• Status: Production Ready - All Tests Passing ✅
• Test Suite: 186+ tests with 100% pass rate
  • ✅ All grammar parsing tests pass
  • ✅ All code generation tests pass
  • ✅ All integration tests pass
  • ✅ All compatibility tests pass
  • ✅ Comprehensive coverage of ANTLR4 features
• Target Languages: 8 languages (Rust, Python, JavaScript, TypeScript, Go, Java, C, C++)
• Package: Single consolidated crate for easy installation
• Grammar Support:
  • ✅ CompleteJSON.g4 - Full JSON grammar
  • ✅ SQL.g4 - SQL grammar subset
  • ✅ 19+ example grammars
  • ✅ Real-world grammars from grammars-v4 repository
• E2E Coverage: Full pipeline testing from grammar to working parser
• ANTLR4 Compatibility: High - supports most common features with comprehensive test coverage
• Latest Features:
  • ✅ Go code generator (idiomatic, production-ready)
  • ✅ Rule arguments: rule[Type name]
  • ✅ Return values: returns [Type name]
  • ✅ Local variables: locals [Type name]
  • ✅ List labels (ids+=ID)
  • ✅ Named actions with code generation

See TODO.md for current tasks and docs/archive/ROADMAP.md for the complete roadmap.

License

Apache-2.0