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feat(convert): add derive macros for To and FromBytes (#667)
closes #661. - [x] docs - [x] tests - [x] depend on `extism-convert/extism-pdk-path` feature in https://github.com/extism/rust-pdk extism/rust-pdk#47
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[package] | ||
name = "extism-convert-macros" | ||
readme = "./README.md" | ||
edition.workspace = true | ||
authors.workspace = true | ||
license.workspace = true | ||
homepage.workspace = true | ||
repository.workspace = true | ||
version.workspace = true | ||
description = "Macros to remove boilerplate with Extism" | ||
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[lib] | ||
proc-macro = true | ||
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[features] | ||
extism-path = [] | ||
extism-pdk-path = [] | ||
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[dependencies] | ||
manyhow.version = "0.11.0" | ||
proc-macro-crate = "3.1.0" | ||
proc-macro2 = "1.0.78" | ||
quote = "1.0.35" | ||
syn = { version = "2.0.48", features = ["derive"] } | ||
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[dev-dependencies] | ||
trybuild = "1.0.89" |
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use std::iter; | ||
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use manyhow::{ensure, error_message, manyhow, Result}; | ||
use proc_macro_crate::{crate_name, FoundCrate}; | ||
use quote::{format_ident, quote, ToTokens}; | ||
use syn::{parse_quote, Attribute, DeriveInput, Path}; | ||
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/// Tries to resolve the path to `extism_convert` dynamically, falling back to feature flags when unsuccessful. | ||
fn convert_path() -> Path { | ||
match ( | ||
crate_name("extism"), | ||
crate_name("extism-convert"), | ||
crate_name("extism-pdk"), | ||
) { | ||
(Ok(FoundCrate::Name(name)), ..) => { | ||
let ident = format_ident!("{name}"); | ||
parse_quote!(::#ident::convert) | ||
} | ||
(_, Ok(FoundCrate::Name(name)), ..) | (.., Ok(FoundCrate::Name(name))) => { | ||
let ident = format_ident!("{name}"); | ||
parse_quote!(::#ident) | ||
} | ||
(Ok(FoundCrate::Itself), ..) => parse_quote!(::extism::convert), | ||
(_, Ok(FoundCrate::Itself), ..) => parse_quote!(::extism_convert), | ||
(.., Ok(FoundCrate::Itself)) => parse_quote!(::extism_pdk), | ||
_ if cfg!(feature = "extism-path") => parse_quote!(::extism::convert), | ||
_ if cfg!(feature = "extism-pdk-path") => parse_quote!(::extism_pdk), | ||
_ => parse_quote!(::extism_convert), | ||
} | ||
} | ||
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fn extract_encoding(attrs: &[Attribute]) -> Result<Path> { | ||
let encodings: Vec<_> = attrs | ||
.iter() | ||
.filter(|attr| attr.path().is_ident("encoding")) | ||
.collect(); | ||
ensure!(!encodings.is_empty(), "encoding needs to be specified"; try = "`#[encoding(ToJson)]`"); | ||
ensure!(encodings.len() < 2, encodings[1], "only one encoding can be specified"; try = "remove `{}`", encodings[1].to_token_stream()); | ||
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Ok(encodings[0].parse_args().map_err( | ||
|e| error_message!(e.span(), "{e}"; note= "expects a path"; try = "`#[encoding(ToJson)]`"), | ||
)?) | ||
} | ||
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#[manyhow] | ||
#[proc_macro_derive(ToBytes, attributes(encoding))] | ||
pub fn to_bytes( | ||
DeriveInput { | ||
attrs, | ||
ident, | ||
generics, | ||
.. | ||
}: DeriveInput, | ||
) -> Result { | ||
let encoding = extract_encoding(&attrs)?; | ||
let convert = convert_path(); | ||
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let (_, type_generics, _) = generics.split_for_impl(); | ||
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let mut generics = generics.clone(); | ||
generics.make_where_clause().predicates.push( | ||
parse_quote!(for<'__to_bytes_b> #encoding<&'__to_bytes_b Self>: #convert::ToBytes<'__to_bytes_b>) | ||
); | ||
generics.params = iter::once(parse_quote!('__to_bytes_a)) | ||
.chain(generics.params) | ||
.collect(); | ||
let (impl_generics, _, where_clause) = generics.split_for_impl(); | ||
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Ok(quote! { | ||
impl #impl_generics #convert::ToBytes<'__to_bytes_a> for #ident #type_generics #where_clause | ||
{ | ||
type Bytes = ::std::vec::Vec<u8>; | ||
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fn to_bytes(&self) -> Result<Self::Bytes, #convert::Error> { | ||
#convert::ToBytes::to_bytes(&#encoding(self)).map(|__bytes| __bytes.as_ref().to_vec()) | ||
} | ||
} | ||
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}) | ||
} | ||
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#[manyhow] | ||
#[proc_macro_derive(FromBytes, attributes(encoding))] | ||
pub fn from_bytes( | ||
DeriveInput { | ||
attrs, | ||
ident, | ||
mut generics, | ||
.. | ||
}: DeriveInput, | ||
) -> Result { | ||
let encoding = extract_encoding(&attrs)?; | ||
let convert = convert_path(); | ||
generics | ||
.make_where_clause() | ||
.predicates | ||
.push(parse_quote!(#encoding<Self>: #convert::FromBytesOwned)); | ||
let (impl_generics, type_generics, where_clause) = generics.split_for_impl(); | ||
Ok(quote! { | ||
impl #impl_generics #convert::FromBytesOwned for #ident #type_generics #where_clause | ||
{ | ||
fn from_bytes_owned(__data: &[u8]) -> Result<Self, #convert::Error> { | ||
<#encoding<Self> as #convert::FromBytesOwned>::from_bytes_owned(__data).map(|__encoding| __encoding.0) | ||
} | ||
} | ||
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}) | ||
} |
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#[test] | ||
fn ui() { | ||
let t = trybuild::TestCases::new(); | ||
t.compile_fail("tests/ui/*.rs"); | ||
} |
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use extism_convert_macros::ToBytes; | ||
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#[derive(ToBytes)] | ||
struct MissingEncoding; | ||
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#[derive(ToBytes)] | ||
#[encoding] | ||
struct EmptyAttr; | ||
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#[derive(ToBytes)] | ||
#[encoding = "string"] | ||
struct EqNoParen; | ||
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#[derive(ToBytes)] | ||
#[encoding(something, else)] | ||
struct NotAPath; | ||
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#[derive(ToBytes)] | ||
#[encoding(Multiple)] | ||
#[encoding(Encodings)] | ||
struct MultipleEncodings; | ||
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fn main() {} |
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error: encoding needs to be specified | ||
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= try: `#[encoding(ToJson)]` | ||
--> tests/ui/invalid-encoding.rs:3:10 | ||
| | ||
3 | #[derive(ToBytes)] | ||
| ^^^^^^^ | ||
| | ||
= note: this error originates in the derive macro `ToBytes` (in Nightly builds, run with -Z macro-backtrace for more info) | ||
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error: expected attribute arguments in parentheses: #[encoding(...)] | ||
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= note: expects a path | ||
= try: `#[encoding(ToJson)]` | ||
--> tests/ui/invalid-encoding.rs:7:3 | ||
| | ||
7 | #[encoding] | ||
| ^^^^^^^^ | ||
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error: expected parentheses: #[encoding(...)] | ||
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= note: expects a path | ||
= try: `#[encoding(ToJson)]` | ||
--> tests/ui/invalid-encoding.rs:11:12 | ||
| | ||
11 | #[encoding = "string"] | ||
| ^ | ||
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error: unexpected token | ||
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= note: expects a path | ||
= try: `#[encoding(ToJson)]` | ||
--> tests/ui/invalid-encoding.rs:15:21 | ||
| | ||
15 | #[encoding(something, else)] | ||
| ^ | ||
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error: only one encoding can be specified | ||
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= try: remove `#[encoding(Encodings)]` | ||
--> tests/ui/invalid-encoding.rs:20:1 | ||
| | ||
20 | #[encoding(Encodings)] | ||
| ^^^^^^^^^^^^^^^^^^^^^^ |
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