Crate genco

A whitespace-aware quasiquoter for beautiful code generation.

Central to genco are the quote! and quote_in! procedural macros which ease the construction of token streams.

This project solves the following language-specific concerns:

• Imports — Generates and groups import statements as they are used. So you only import what you use, with no redundancy. We also do our best to solve namespace conflicts.

• String Quoting — genco knows how to quote strings. And can even interpolate values into the quoted string if it’s supported by the language.

• Structural Indentation — The quoter relies on intuitive whitespace detection to structurally sort out spacings and indentation. Allowing genco to generate beautiful readable code with minimal effort. This is also a requirement for generating correctly behaving code in languages like Python where indentation is meaningful.

• Language Customization — Building support for new languages is a piece of cake with the help of the impl_lang! macro.

To support line changes during whitespace detection, we depend on the nightly proc_macro_span feature. On stable we can only detect column changes.

Until this is stabilized and you want fully functional whitespace detection you must build and run projects using genco with a nightly compiler. This is important for whitespace-sensitive languages like python.

You can try the difference between:

cargo run --example rust

And:

cargo +nightly run --example rust

Supported Languages

The following are languages which have built-in support in genco.

• 🦀 Rust
  Example

• ☕ Java
  Example

• 🎼 C#
  Example

• 🐿️ Go
  Example

• 🎯 Dart
  Example

• 🌐 JavaScript
  Example

• 🇨 C
  Example

• 🐍 Python
  Example
  Requires a nightly compiler

Is your favorite language missing? Open an issue!

You can run one of the examples by:

cargo +nightly run --example rust

Rust Example

The following is a simple program producing Rust code to stdout with custom configuration:

use genco::prelude::*;

let hash_map = rust::import("std::collections", "HashMap");

let tokens: rust::Tokens = quote! {
    fn main() {
        let mut m = $hash_map::new();
        m.insert(1u32, 2u32);
    }
};

println!("{}", tokens.to_file_string()?);

This would produce:

use std::collections::HashMap;

fn main() {
    let mut m = HashMap::new();
    m.insert(1u32, 2u32);
}

Re-exports

• pub use self::tokens::Tokens;

Modules

• fmt
  Code formatting utilities.
• lang
  Language specialization for genco
• prelude
  Prelude containing typical things to import when using the library.
• tokens
  Utilities for working with token streams.

Macros

• impl_lang
  Macro to implement support for a custom language.
• quote
  Whitespace sensitive quasi-quoting.
• quote_fn
  Convenience macro for constructing a FormatInto implementation in-place.
• quote_in
  Behaves the same as quote! while quoting into an existing token stream with <target> => <quoted>.