add ComponentType/Lift/Lower derive macro for record types (#4337)
This is the first stage of implementing https://github.com/bytecodealliance/wasmtime/issues/4308, i.e. derive macros for `ComponentType`, `Lift`, and `Lower` for composite types in the component model. This stage only covers records; I expect the other composite types will follow a similar pattern. It borrows heavily from the work Jamey Sharp did in https://github.com/bytecodealliance/wasmtime/pull/4217. Thanks for that, and thanks to both Jamey and Alex Crichton for their excellent review feedback. Thanks also to Brian for pairing up on the initial draft. Signed-off-by: Joel Dice <joel.dice@fermyon.com>
This commit is contained in:
Joel Dice
22
crates/component-macro/Cargo.toml
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22
crates/component-macro/Cargo.toml
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[package]
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name = "wasmtime-component-macro"
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version = "0.39.0"
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authors = ["The Wasmtime Project Developers"]
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description = "Macros for deriving component interface types from Rust types"
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license = "Apache-2.0 WITH LLVM-exception"
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repository = "https://github.com/bytecodealliance/wasmtime"
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documentation = "https://docs.rs/wasmtime-component-macro/"
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categories = ["wasm"]
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keywords = ["webassembly", "wasm"]
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edition = "2021"
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[lib]
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proc-macro = true
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[dependencies]
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proc-macro2 = "1.0"
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quote = "1.0"
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syn = { version = "1.0", features = ["extra-traits"] }
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[badges]
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maintenance = { status = "actively-developed" }
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382
crates/component-macro/src/lib.rs
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382
crates/component-macro/src/lib.rs
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use proc_macro2::{Literal, TokenStream, TokenTree};
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use quote::{format_ident, quote};
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use std::collections::HashSet;
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use syn::{parse_macro_input, parse_quote, Data, DeriveInput, Error, Result};
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#[derive(Debug)]
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enum Style {
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Record,
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Variant,
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Enum,
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Union,
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}
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fn find_style(input: &DeriveInput) -> Result<Style> {
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let mut style = None;
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for attribute in &input.attrs {
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if attribute.path.leading_colon.is_some() || attribute.path.segments.len() != 1 {
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continue;
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}
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let ident = &attribute.path.segments[0].ident;
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if "component" != &ident.to_string() {
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continue;
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}
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let syntax_error = || {
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Err(Error::new_spanned(
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&attribute.tokens,
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"expected `component(<style>)` syntax",
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))
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};
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let style_string = if let [TokenTree::Group(group)] =
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&attribute.tokens.clone().into_iter().collect::<Vec<_>>()[..]
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{
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if let [TokenTree::Ident(style)] = &group.stream().into_iter().collect::<Vec<_>>()[..] {
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style.to_string()
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} else {
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return syntax_error();
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}
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} else {
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return syntax_error();
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};
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if style.is_some() {
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return Err(Error::new(ident.span(), "duplicate `component` attribute"));
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}
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style = Some(match style_string.as_ref() {
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"record" => Style::Record,
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"variant" => Style::Variant,
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"enum" => Style::Enum,
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"union" => Style::Union,
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"flags" => {
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return Err(Error::new_spanned(
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&attribute.tokens,
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"`flags` not allowed here; \
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use `wasmtime::component::flags!` macro to define `flags` types",
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))
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}
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_ => {
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return Err(Error::new_spanned(
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&attribute.tokens,
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"unrecognized component type keyword \
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(expected `record`, `variant`, `enum`, or `union`)",
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))
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}
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});
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}
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style.ok_or_else(|| Error::new_spanned(input, "missing `component` attribute"))
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}
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fn find_rename(field: &syn::Field) -> Result<Option<Literal>> {
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let mut name = None;
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for attribute in &field.attrs {
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if attribute.path.leading_colon.is_some() || attribute.path.segments.len() != 1 {
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continue;
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}
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let ident = &attribute.path.segments[0].ident;
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if "component" != &ident.to_string() {
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continue;
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}
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let syntax_error = || {
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Err(Error::new_spanned(
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&attribute.tokens,
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"expected `component(name = <name literal>)` syntax",
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))
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};
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let name_literal = if let [TokenTree::Group(group)] =
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&attribute.tokens.clone().into_iter().collect::<Vec<_>>()[..]
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{
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match &group.stream().into_iter().collect::<Vec<_>>()[..] {
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[TokenTree::Ident(key), TokenTree::Punct(op), TokenTree::Literal(literal)]
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if "name" == &key.to_string() && '=' == op.as_char() =>
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{
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literal.clone()
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}
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_ => return syntax_error(),
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}
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} else {
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return syntax_error();
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};
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if name.is_some() {
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return Err(Error::new(ident.span(), "duplicate field rename attribute"));
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}
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name = Some(name_literal);
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}
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Ok(name)
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}
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fn add_trait_bounds(generics: &syn::Generics) -> syn::Generics {
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let mut generics = generics.clone();
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for param in &mut generics.params {
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if let syn::GenericParam::Type(ref mut type_param) = *param {
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type_param
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.bounds
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.push(parse_quote!(wasmtime::component::ComponentType));
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}
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}
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generics
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}
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trait Expander {
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fn expand_record(&self, input: &DeriveInput, fields: &syn::FieldsNamed) -> Result<TokenStream>;
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// TODO: expand_variant, expand_enum, etc.
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}
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fn expand(expander: &dyn Expander, input: DeriveInput) -> Result<TokenStream> {
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match find_style(&input)? {
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Style::Record => expand_record(expander, input),
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style => Err(Error::new_spanned(input, format!("todo: expand {style:?}"))),
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}
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}
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fn expand_record(expander: &dyn Expander, input: DeriveInput) -> Result<TokenStream> {
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let name = &input.ident;
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let body = if let Data::Struct(body) = &input.data {
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body
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} else {
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return Err(Error::new(
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name.span(),
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"`record` component types can only be derived for `struct`s",
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));
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};
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match &body.fields {
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syn::Fields::Named(fields) => expander.expand_record(&input, fields),
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syn::Fields::Unnamed(_) | syn::Fields::Unit => Err(Error::new(
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name.span(),
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"`record` component types can only be derived for `struct`s with named fields",
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)),
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}
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}
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#[proc_macro_derive(Lift, attributes(component))]
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pub fn lift(input: proc_macro::TokenStream) -> proc_macro::TokenStream {
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expand(&LiftExpander, parse_macro_input!(input as DeriveInput))
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.unwrap_or_else(Error::into_compile_error)
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.into()
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}
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struct LiftExpander;
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impl Expander for LiftExpander {
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fn expand_record(&self, input: &DeriveInput, fields: &syn::FieldsNamed) -> Result<TokenStream> {
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let internal = quote!(wasmtime::component::__internal);
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let mut lifts = TokenStream::new();
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let mut loads = TokenStream::new();
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for syn::Field { ty, ident, .. } in &fields.named {
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lifts.extend(quote!(#ident: <#ty as wasmtime::component::Lift>::lift(
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store, options, &src.#ident
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)?,));
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loads.extend(quote!(#ident: <#ty as wasmtime::component::Lift>::load(
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memory,
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&bytes
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[#internal::next_field::<#ty>(&mut offset)..]
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[..<#ty as wasmtime::component::ComponentType>::size()]
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)?,));
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}
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let name = &input.ident;
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let generics = add_trait_bounds(&input.generics);
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let (impl_generics, ty_generics, where_clause) = generics.split_for_impl();
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let expanded = quote! {
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unsafe impl #impl_generics wasmtime::component::Lift for #name #ty_generics #where_clause {
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#[inline]
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fn lift(
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store: &#internal::StoreOpaque,
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options: &#internal::Options,
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src: &Self::Lower,
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) -> #internal::anyhow::Result<Self> {
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Ok(Self {
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#lifts
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})
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}
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#[inline]
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fn load(memory: &#internal::Memory, bytes: &[u8]) -> #internal::anyhow::Result<Self> {
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debug_assert!(
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(bytes.as_ptr() as usize)
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% (<Self as wasmtime::component::ComponentType>::align() as usize)
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== 0
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);
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let mut offset = 0;
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Ok(Self {
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#loads
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})
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}
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}
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};
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Ok(expanded)
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}
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}
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#[proc_macro_derive(Lower, attributes(component))]
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pub fn lower(input: proc_macro::TokenStream) -> proc_macro::TokenStream {
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expand(&LowerExpander, parse_macro_input!(input as DeriveInput))
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.unwrap_or_else(Error::into_compile_error)
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.into()
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}
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struct LowerExpander;
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impl Expander for LowerExpander {
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fn expand_record(&self, input: &DeriveInput, fields: &syn::FieldsNamed) -> Result<TokenStream> {
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let internal = quote!(wasmtime::component::__internal);
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let mut lowers = TokenStream::new();
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let mut stores = TokenStream::new();
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for syn::Field { ty, ident, .. } in &fields.named {
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lowers.extend(quote!(wasmtime::component::Lower::lower(
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&self.#ident, store, options, #internal::map_maybe_uninit!(dst.#ident)
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)?;));
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stores.extend(quote!(wasmtime::component::Lower::store(
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&self.#ident, memory, #internal::next_field::<#ty>(&mut offset)
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)?;));
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}
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let name = &input.ident;
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let generics = add_trait_bounds(&input.generics);
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let (impl_generics, ty_generics, where_clause) = generics.split_for_impl();
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let expanded = quote! {
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unsafe impl #impl_generics wasmtime::component::Lower for #name #ty_generics #where_clause {
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#[inline]
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fn lower<T>(
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&self,
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store: &mut wasmtime::StoreContextMut<T>,
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options: &#internal::Options,
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dst: &mut std::mem::MaybeUninit<Self::Lower>,
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) -> #internal::anyhow::Result<()> {
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#lowers
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Ok(())
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}
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#[inline]
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fn store<T>(
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&self,
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memory: &mut #internal::MemoryMut<'_, T>,
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mut offset: usize
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) -> #internal::anyhow::Result<()> {
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#stores
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Ok(())
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}
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}
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};
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Ok(expanded)
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}
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}
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#[proc_macro_derive(ComponentType, attributes(component))]
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pub fn component_type(input: proc_macro::TokenStream) -> proc_macro::TokenStream {
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expand(
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&ComponentTypeExpander,
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parse_macro_input!(input as DeriveInput),
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)
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.unwrap_or_else(Error::into_compile_error)
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.into()
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}
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struct ComponentTypeExpander;
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impl Expander for ComponentTypeExpander {
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fn expand_record(&self, input: &DeriveInput, fields: &syn::FieldsNamed) -> Result<TokenStream> {
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let internal = quote!(wasmtime::component::__internal);
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let mut field_names_and_checks = TokenStream::new();
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let mut lower_field_declarations = TokenStream::new();
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let mut sizes = TokenStream::new();
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let mut unique_types = HashSet::new();
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for field @ syn::Field { ty, ident, .. } in &fields.named {
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lower_field_declarations
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.extend(quote!(#ident: <#ty as wasmtime::component::ComponentType>::Lower,));
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let literal = find_rename(field)?
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.unwrap_or_else(|| Literal::string(&ident.as_ref().unwrap().to_string()));
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field_names_and_checks.extend(
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quote!((#literal, <#ty as wasmtime::component::ComponentType>::typecheck),),
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);
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sizes.extend(quote!(#internal::next_field::<#ty>(&mut size);));
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unique_types.insert(ty);
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}
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let alignments = unique_types
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.into_iter()
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.map(|ty| {
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quote!(align = align.max(
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<#ty as wasmtime::component::ComponentType>::align()
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);)
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})
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.collect::<TokenStream>();
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let name = &input.ident;
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let generics = add_trait_bounds(&input.generics);
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let (impl_generics, ty_generics, where_clause) = generics.split_for_impl();
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let lower = format_ident!("_Lower{}", name);
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let expanded = quote! {
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#[doc(hidden)]
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#[derive(Clone, Copy)]
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#[repr(C)]
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pub struct #lower {
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#lower_field_declarations
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}
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unsafe impl #impl_generics wasmtime::component::ComponentType for #name #ty_generics #where_clause {
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type Lower = #lower;
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#[inline]
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fn typecheck(
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ty: &#internal::InterfaceType,
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types: &#internal::ComponentTypes,
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) -> #internal::anyhow::Result<()> {
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#internal::typecheck_record(ty, types, &[#field_names_and_checks])
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}
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#[inline]
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fn size() -> usize {
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let mut size = 0;
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#sizes
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size
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}
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#[inline]
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fn align() -> u32 {
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let mut align = 1;
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#alignments
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align
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}
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}
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};
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Ok(quote!(const _: () = { #expanded };))
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}
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}
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