#template #code-generation

macro genco-macros

A whitespace-aware quasiquoter for beautiful code generation

38 releases (10 breaking)

new 0.15.1 Oct 13, 2020
0.15.0 Jun 27, 2020
0.14.2 Jun 21, 2020

#71 in Template engine

Download history 54/week @ 2020-06-25 92/week @ 2020-07-02 45/week @ 2020-07-09 55/week @ 2020-07-16 111/week @ 2020-07-23 1/week @ 2020-07-30 49/week @ 2020-08-06 78/week @ 2020-08-13 41/week @ 2020-08-20 80/week @ 2020-08-27 79/week @ 2020-09-03 42/week @ 2020-09-10 7/week @ 2020-09-17 6/week @ 2020-09-24 41/week @ 2020-10-01 24/week @ 2020-10-08

198 downloads per month
Used in 3 crates (via genco)


1.5K SLoC

Build Status crates.io docs.rs


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 do whitespace detection, we depend on the nightly proc_macro_span feature.

Until this is stabilized, you must build and run projects using genco with a nightly compiler.

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);


~21K SLoC