Crate derive_deftly
source ·Expand description
§derive-deftly: An ergonomic replacement for (some) 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.
Stability warning
We intend to make a 1.x release of this crate fairly soon. But, before 1.0, we intend to make a number of breaking changes.
This is the replacement for
derive-adhoc
.
We recommend that existing derive-adhoc
users upgrade to derive-deftly
,
at some time that is convenient.
§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.
Further documentation is available in the doc_
module(s)
and the docs for the individual proc macros.
§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 introduction?
It will walk you through derive-deftly’s most important features, with a number of worked examples,
Modules§
- Changelog, MSRV policy and cargo features
- Implementation approach - how does this work?
- Introduction to derive-deftly
- Template syntax (and expansion options) reference
Macros§
- Define a reuseable template
- Expand an ad-hoc template, on a data structure decorated
#[derive_deftly_adhoc]
- Template expansion engine, internal
- Check semver compatibility, for a crate which exports macros
Derive Macros§
- Perform ad-hoc templating driven by a data structure