#template #code-generation


A whitespace-aware quasiquoter for beautiful code generation

98 releases

0.17.2 Sep 15, 2022
0.17.1 Jul 10, 2022
0.17.0 Jun 30, 2022
0.16.1 Mar 25, 2022
0.1.11 Nov 22, 2017

#7 in Template engine

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Used in 28 crates (20 directly)


3.5K SLoC


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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


cargo +nightly run --example rust

Supported Languages

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

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);

License: MIT/Apache-2.0


~18K SLoC