genco

genco is an even simpler code generator for Rust, written for use in reproto.

We depend on proc_macro_hygiene stabilizations. Until then, you must build with the nightly branch.

cargo +nightly run --example rust

The workhorse of genco is the quote! macro. While tokens can be constructed manually, quote! makes this process much easier.

genco only minimally deals with language-specific syntax, but primarily deals with solving the following:

• Generates and groups import statements.
• Quote (and escape) strings using <stmt>.quoted().
• Indents and spaces your code according to generic indentation rules that can be tweaked on a per-language basis.

Examples

The following are language specific examples for genco using the quote! macro.

• Rust Example
• Java Example
• C# Example
• Go Example
• Dart Example (TODO)
• JavaScript Example (TODO)
• Python Example (TODO)

You can run one of the examples above using:

cargo run --example go

The following is the included example Rust program.

use genco::rust::{imported, Config};
use genco::{quote, FormatterConfig, Rust};
use rand::Rng;

use std::fmt;

fn main() -> fmt::Result {
    // Import the LittleEndian item, without referencing it through the last
    // module component it is part of.
    let little_endian = imported("byteorder", "LittleEndian");
    let big_endian = imported("byteorder", "BigEndian").prefixed();

    // This is a trait, so only import it into the scope (unless we intent to
    // implement it).
    let write_bytes_ext = imported("byteorder", "WriteBytesExt").alias("_");
    let read_bytes_ext = imported("byteorder", "ReadBytesExt").alias("_");

    let tokens = quote! {
        // Markup used for imports without an immediate use.
        #@(write_bytes_ext)
        #@(read_bytes_ext)

        fn test() {
            let mut wtr = vec![];
            wtr.write_u16::<#little_endian>(517).unwrap();
            wtr.write_u16::<#big_endian>(768).unwrap();
        }
    };

    // Simpler printing with default indentation:
    // println!("{}", tokens.to_file_string()?);

    tokens.to_io_writer_with(
        std::io::stdout().lock(),
        Config::default(),
        FormatterConfig::from_lang::<Rust>().with_indentation(2),
    )?;

    Ok(())
}

Indentation Rules

The quote! macro has the following rules for dealing with indentation and spacing.

Two tokens that are separated, are spaced. Regardless of how many spaces there are between them.

So:

let _: genco::Tokens<genco::Rust> = genco::quote!(fn   test() {});

Becomes:

fn test() {}

More that two line breaks are collapsed.

So:

let _: genco::Tokens<genco::Rust> = genco::quote! {
    fn test() {
        println!("Hello...");


        println!("... World!");
    }
};

Becomes:

fn test() {
    println!("Hello...");

    println!("... World!");
}

Indentation is determined on a row-by-row basis. If a column is further in than the one on the preceeding row, it is indented one level deeper.

Like wise if a column starts before the previous rows column, it is indended one level shallower.

So:

let _: genco::Tokens<genco::Rust> = genco::quote! {
  fn test() {
      println!("Hello...");
      println!("... World!");
    }
};

Becomes:

fn test() {
    println!("Hello...");
    println!("... World!");
}