Crate derive_deftly

Expand description

§derive-deftly: An ergonomic replacement for many proc macros

derive-deftly allows you to write macros which are driven by Rust data structures, just like proc macro derive macros, but without having to wrestle with the proc macro system.

§Overview

You can write an ad-hoc template, which can speak about the fields and types in the data structure. You can also define named templates and apply them to multiple structures: effectively, you can define your own derive macro.

You don’t need to make a separate proc macro crate, write to the syn and proc_macro APIs. take care to properly propagate compile errors, or, generally, do any of the things that make writing proc macros so complicated.

The template language resembles the “expander” part of a macro_rules macro, but you don’t have to write the “matcher” part: derive-deftly parses the input data structure for you, and makes the pieces available via predefined expansion variables.

Full documentation is available in the doc_ module(s), the docs for the individual proc macros, and the Guide.

§Simple example - providing `Vec` containing enum variant names

use derive_deftly::{define_derive_deftly, Deftly};

define_derive_deftly! {
    ListVariants:

    impl $ttype {
        fn list_variants() -> Vec<&'static str> {
            vec![ $( stringify!( $vname ) , ) ]
        }
    }
}

#[derive(Deftly)]
#[derive_deftly(ListVariants)]
enum Enum {
    UnitVariant,
    StructVariant { a: u8, b: u16 },
    TupleVariant(u8, u16),
}

assert_eq!(
    Enum::list_variants(),
    ["UnitVariant", "StructVariant", "TupleVariant"],
);

§Next steps

Why not have a look at our friendly user guide? It will walk you through derive-deftly’s most important features, with a number of worked examples.

Alternatively, there is comprehensive reference documentation.

§derive-deftly documentation, overall table of contents

Guide: Tutorial and walkthrough, in book form

Modules§

doc_changelog: Changelog, MSRV policy and cargo features
doc_implementation: Implementation approach - how does this work?
doc_reference: Template syntax (and expansion options) reference

Macros§

define_derive_deftly: Define a reuseable template
derive_deftly_adhoc: Expand an ad-hoc template, on a data structure decorated #[derive_deftly_adhoc]
derive_deftly_engine: Template expansion engine, internal
template_export_semver_check: Check semver compatibility, for a crate which exports macros

Derive Macros§

Deftly: Perform ad-hoc templating driven by a data structure