mozilla-central/third_party/rust/diplomat/src/lib.rs

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use proc_macro2::Span;
use quote::{quote, ToTokens};
use syn::*;
use diplomat_core::ast;
mod enum_convert;
mod transparent_convert;
fn cfgs_to_stream(attrs: &[Attribute]) -> proc_macro2::TokenStream {
attrs
.iter()
.fold(quote!(), |prev, attr| quote!(#prev #attr))
}
fn gen_params_at_boundary(param: &ast::Param, expanded_params: &mut Vec<FnArg>) {
match &param.ty {
ast::TypeName::StrReference(
..,
ast::StringEncoding::UnvalidatedUtf8
| ast::StringEncoding::UnvalidatedUtf16
| ast::StringEncoding::Utf8,
)
| ast::TypeName::PrimitiveSlice(..)
| ast::TypeName::StrSlice(..) => {
let data_type = if let ast::TypeName::PrimitiveSlice(.., prim) = &param.ty {
ast::TypeName::Primitive(*prim).to_syn().to_token_stream()
} else if let ast::TypeName::StrReference(
_,
ast::StringEncoding::UnvalidatedUtf8 | ast::StringEncoding::Utf8,
) = &param.ty
{
quote! { u8 }
} else if let ast::TypeName::StrReference(_, ast::StringEncoding::UnvalidatedUtf16) =
&param.ty
{
quote! { u16 }
} else if let ast::TypeName::StrSlice(ast::StringEncoding::Utf8) = &param.ty {
// TODO: this is not an ABI-stable type!
quote! { &str }
} else if let ast::TypeName::StrSlice(ast::StringEncoding::UnvalidatedUtf8) = &param.ty
{
// TODO: this is not an ABI-stable type!
quote! { &[u8] }
} else if let ast::TypeName::StrSlice(ast::StringEncoding::UnvalidatedUtf16) = &param.ty
{
// TODO: this is not an ABI-stable type!
quote! { &[u16] }
} else {
unreachable!()
};
expanded_params.push(FnArg::Typed(PatType {
attrs: vec![],
pat: Box::new(Pat::Ident(PatIdent {
attrs: vec![],
by_ref: None,
mutability: None,
ident: Ident::new(&format!("{}_diplomat_data", param.name), Span::call_site()),
subpat: None,
})),
colon_token: syn::token::Colon(Span::call_site()),
ty: Box::new(
parse2({
if let ast::TypeName::PrimitiveSlice(
Some((_, ast::Mutability::Mutable)) | None,
_,
)
| ast::TypeName::StrReference(None, ..) = &param.ty
{
quote! { *mut #data_type }
} else {
quote! { *const #data_type }
}
})
.unwrap(),
),
}));
expanded_params.push(FnArg::Typed(PatType {
attrs: vec![],
pat: Box::new(Pat::Ident(PatIdent {
attrs: vec![],
by_ref: None,
mutability: None,
ident: Ident::new(&format!("{}_diplomat_len", param.name), Span::call_site()),
subpat: None,
})),
colon_token: syn::token::Colon(Span::call_site()),
ty: Box::new(
parse2(quote! {
usize
})
.unwrap(),
),
}));
}
o => {
expanded_params.push(FnArg::Typed(PatType {
attrs: vec![],
pat: Box::new(Pat::Ident(PatIdent {
attrs: vec![],
by_ref: None,
mutability: None,
ident: Ident::new(param.name.as_str(), Span::call_site()),
subpat: None,
})),
colon_token: syn::token::Colon(Span::call_site()),
ty: Box::new(o.to_syn()),
}));
}
}
}
fn gen_params_invocation(param: &ast::Param, expanded_params: &mut Vec<Expr>) {
match &param.ty {
ast::TypeName::StrReference(..)
| ast::TypeName::PrimitiveSlice(..)
| ast::TypeName::StrSlice(..) => {
let data_ident =
Ident::new(&format!("{}_diplomat_data", param.name), Span::call_site());
let len_ident = Ident::new(&format!("{}_diplomat_len", param.name), Span::call_site());
let tokens = if let ast::TypeName::PrimitiveSlice(lm, _) = &param.ty {
match lm {
Some((_, ast::Mutability::Mutable)) => quote! {
if #len_ident == 0 {
&mut []
} else {
unsafe { core::slice::from_raw_parts_mut(#data_ident, #len_ident) }
}
},
Some((_, ast::Mutability::Immutable)) => quote! {
if #len_ident == 0 {
&[]
} else {
unsafe { core::slice::from_raw_parts(#data_ident, #len_ident) }
}
},
None => quote! {
if #len_ident == 0 {
Default::default()
} else {
unsafe { alloc::boxed::Box::from_raw(core::ptr::slice_from_raw_parts_mut(#data_ident, #len_ident)) }
}
},
}
} else if let ast::TypeName::StrReference(Some(_), encoding) = &param.ty {
let encode = match encoding {
ast::StringEncoding::Utf8 => quote! {
// The FFI guarantees this, by either validating, or communicating this requirement to the user.
unsafe { core::str::from_utf8_unchecked(core::slice::from_raw_parts(#data_ident, #len_ident)) }
},
_ => quote! {
unsafe { core::slice::from_raw_parts(#data_ident, #len_ident) }
},
};
quote! {
if #len_ident == 0 {
Default::default()
} else {
#encode
}
}
} else if let ast::TypeName::StrReference(None, encoding) = &param.ty {
let encode = match encoding {
ast::StringEncoding::Utf8 => quote! {
unsafe { core::str::from_boxed_utf8_unchecked(alloc::boxed::Box::from_raw(core::ptr::slice_from_raw_parts_mut(#data_ident, #len_ident))) }
},
_ => quote! {
unsafe { alloc::boxed::Box::from_raw(core::ptr::slice_from_raw_parts_mut(#data_ident, #len_ident)) }
},
};
quote! {
if #len_ident == 0 {
Default::default()
} else {
#encode
}
}
} else if let ast::TypeName::StrSlice(_) = &param.ty {
quote! {
if #len_ident == 0 {
&[]
} else {
unsafe { core::slice::from_raw_parts(#data_ident, #len_ident) }
}
}
} else {
unreachable!();
};
expanded_params.push(parse2(tokens).unwrap());
}
ast::TypeName::Result(_, _, _) => {
let param = &param.name;
expanded_params.push(parse2(quote!(#param.into())).unwrap());
}
_ => {
expanded_params.push(Expr::Path(ExprPath {
attrs: vec![],
qself: None,
path: Ident::new(param.name.as_str(), Span::call_site()).into(),
}));
}
}
}
fn gen_custom_type_method(strct: &ast::CustomType, m: &ast::Method) -> Item {
let self_ident = Ident::new(strct.name().as_str(), Span::call_site());
let method_ident = Ident::new(m.name.as_str(), Span::call_site());
let extern_ident = Ident::new(m.full_path_name.as_str(), Span::call_site());
let mut all_params = vec![];
m.params.iter().for_each(|p| {
gen_params_at_boundary(p, &mut all_params);
});
let mut all_params_invocation = vec![];
m.params.iter().for_each(|p| {
gen_params_invocation(p, &mut all_params_invocation);
});
let this_ident = Pat::Ident(PatIdent {
attrs: vec![],
by_ref: None,
mutability: None,
ident: Ident::new("this", Span::call_site()),
subpat: None,
});
if let Some(self_param) = &m.self_param {
all_params.insert(
0,
FnArg::Typed(PatType {
attrs: vec![],
pat: Box::new(this_ident.clone()),
colon_token: syn::token::Colon(Span::call_site()),
ty: Box::new(self_param.to_typename().to_syn()),
}),
);
}
let lifetimes = {
let lifetime_env = &m.lifetime_env;
if lifetime_env.is_empty() {
quote! {}
} else {
quote! { <#lifetime_env> }
}
};
let method_invocation = if m.self_param.is_some() {
quote! { #this_ident.#method_ident }
} else {
quote! { #self_ident::#method_ident }
};
let (return_tokens, maybe_into) = if let Some(return_type) = &m.return_type {
if let ast::TypeName::Result(ok, err, true) = return_type {
let ok = ok.to_syn();
let err = err.to_syn();
(
quote! { -> diplomat_runtime::DiplomatResult<#ok, #err> },
quote! { .into() },
)
} else if let ast::TypeName::Ordering = return_type {
let return_type_syn = return_type.to_syn();
(quote! { -> #return_type_syn }, quote! { as i8 })
} else if let ast::TypeName::Option(ty) = return_type {
match ty.as_ref() {
// pass by reference, Option becomes null
ast::TypeName::Box(..) | ast::TypeName::Reference(..) => {
let return_type_syn = return_type.to_syn();
(quote! { -> #return_type_syn }, quote! {})
}
// anything else goes through DiplomatResult
_ => {
let ty = ty.to_syn();
(
quote! { -> diplomat_runtime::DiplomatResult<#ty, ()> },
quote! { .ok_or(()).into() },
)
}
}
} else {
let return_type_syn = return_type.to_syn();
(quote! { -> #return_type_syn }, quote! {})
}
} else {
(quote! {}, quote! {})
};
let writeable_flushes = m
.params
.iter()
.filter(|p| p.is_writeable())
.map(|p| {
let p = &p.name;
quote! { #p.flush(); }
})
.collect::<Vec<_>>();
let cfg = cfgs_to_stream(&m.attrs.cfg);
if writeable_flushes.is_empty() {
Item::Fn(syn::parse_quote! {
#[no_mangle]
#cfg
extern "C" fn #extern_ident#lifetimes(#(#all_params),*) #return_tokens {
#method_invocation(#(#all_params_invocation),*) #maybe_into
}
})
} else {
Item::Fn(syn::parse_quote! {
#[no_mangle]
#cfg
extern "C" fn #extern_ident#lifetimes(#(#all_params),*) #return_tokens {
let ret = #method_invocation(#(#all_params_invocation),*);
#(#writeable_flushes)*
ret #maybe_into
}
})
}
}
struct AttributeInfo {
repr: bool,
opaque: bool,
is_out: bool,
}
impl AttributeInfo {
fn extract(attrs: &mut Vec<Attribute>) -> Self {
let mut repr = false;
let mut opaque = false;
let mut is_out = false;
attrs.retain(|attr| {
let ident = &attr.path().segments.iter().next().unwrap().ident;
if ident == "repr" {
repr = true;
// don't actually extract repr attrs, just detect them
return true;
} else if ident == "diplomat" {
if attr.path().segments.len() == 2 {
let seg = &attr.path().segments.iter().nth(1).unwrap().ident;
if seg == "opaque" {
opaque = true;
return false;
} else if seg == "out" {
is_out = true;
return false;
} else if seg == "rust_link"
|| seg == "out"
|| seg == "attr"
|| seg == "skip_if_ast"
|| seg == "abi_rename"
{
// diplomat-tool reads these, not diplomat::bridge.
// throw them away so rustc doesn't complain about unknown attributes
return false;
} else if seg == "enum_convert" || seg == "transparent_convert" {
// diplomat::bridge doesn't read this, but it's handled separately
// as an attribute
return true;
} else {
panic!("Only #[diplomat::opaque] and #[diplomat::rust_link] are supported")
}
} else {
panic!("#[diplomat::foo] attrs have a single-segment path name")
}
}
true
});
Self {
repr,
opaque,
is_out,
}
}
}
fn gen_bridge(mut input: ItemMod) -> ItemMod {
let module = ast::Module::from_syn(&input, true);
// Clean out any diplomat attributes so Rust doesn't get mad
let _attrs = AttributeInfo::extract(&mut input.attrs);
let (brace, mut new_contents) = input.content.unwrap();
new_contents.push(parse2(quote! { use diplomat_runtime::*; }).unwrap());
new_contents.iter_mut().for_each(|c| match c {
Item::Struct(s) => {
let info = AttributeInfo::extract(&mut s.attrs);
// Normal opaque types don't need repr(transparent) because the inner type is
// never referenced. #[diplomat::transparent_convert] handles adding repr(transparent)
// on its own
if !info.opaque {
let copy = if !info.is_out {
// Nothing stops FFI from copying, so we better make sure the struct is Copy.
quote!(#[derive(Clone, Copy)])
} else {
quote!()
};
let repr = if !info.repr {
quote!(#[repr(C)])
} else {
quote!()
};
*s = syn::parse_quote! {
#repr
#copy
#s
}
}
}
Item::Enum(e) => {
let info = AttributeInfo::extract(&mut e.attrs);
if info.opaque {
panic!("#[diplomat::opaque] not allowed on enums")
}
for v in &mut e.variants {
let info = AttributeInfo::extract(&mut v.attrs);
if info.opaque {
panic!("#[diplomat::opaque] not allowed on enum variants");
}
}
*e = syn::parse_quote! {
#[repr(C)]
#[derive(Clone, Copy)]
#e
};
}
Item::Impl(i) => {
for item in &mut i.items {
if let syn::ImplItem::Fn(ref mut m) = *item {
let info = AttributeInfo::extract(&mut m.attrs);
if info.opaque {
panic!("#[diplomat::opaque] not allowed on methods")
}
}
}
}
_ => (),
});
for custom_type in module.declared_types.values() {
custom_type.methods().iter().for_each(|m| {
new_contents.push(gen_custom_type_method(custom_type, m));
});
let destroy_ident = Ident::new(custom_type.dtor_name().as_str(), Span::call_site());
let type_ident = custom_type.name().to_syn();
let (lifetime_defs, lifetimes) = if let Some(lifetime_env) = custom_type.lifetimes() {
(
quote! { <#lifetime_env> },
lifetime_env.lifetimes_to_tokens(),
)
} else {
(quote! {}, quote! {})
};
let cfg = cfgs_to_stream(&custom_type.attrs().cfg);
// for now, body is empty since all we need to do is drop the box
// TODO(#13): change to take a `*mut` and handle DST boxes appropriately
new_contents.push(Item::Fn(syn::parse_quote! {
#[no_mangle]
#cfg
extern "C" fn #destroy_ident#lifetime_defs(this: Box<#type_ident#lifetimes>) {}
}));
}
ItemMod {
attrs: input.attrs,
vis: input.vis,
mod_token: input.mod_token,
ident: input.ident,
content: Some((brace, new_contents)),
semi: input.semi,
unsafety: None,
}
}
/// Mark a module to be exposed through Diplomat-generated FFI.
#[proc_macro_attribute]
pub fn bridge(
_attr: proc_macro::TokenStream,
input: proc_macro::TokenStream,
) -> proc_macro::TokenStream {
let expanded = gen_bridge(parse_macro_input!(input));
proc_macro::TokenStream::from(expanded.to_token_stream())
}
/// Generate From and Into implementations for a Diplomat enum
///
/// This is invoked as `#[diplomat::enum_convert(OtherEnumName)]`
/// on a Diplomat enum. It will assume the other enum has exactly the same variants
/// and generate From and Into implementations using those. In case that enum is `#[non_exhaustive]`,
/// you may use `#[diplomat::enum_convert(OtherEnumName, needs_wildcard)]` to generate a panicky wildcard
/// branch. It is up to the library author to ensure the enums are kept in sync. You may use the `#[non_exhaustive_omitted_patterns]`
/// lint to enforce this.
#[proc_macro_attribute]
pub fn enum_convert(
attr: proc_macro::TokenStream,
input: proc_macro::TokenStream,
) -> proc_macro::TokenStream {
// proc macros handle compile errors by using special error tokens.
// In case of an error, we don't want the original code to go away too
// (otherwise that will cause more errors) so we hold on to it and we tack it in
// with no modifications below
let input_cached: proc_macro2::TokenStream = input.clone().into();
let expanded =
enum_convert::gen_enum_convert(parse_macro_input!(attr), parse_macro_input!(input));
let full = quote! {
#expanded
#input_cached
};
proc_macro::TokenStream::from(full.to_token_stream())
}
/// Generate conversions from inner types for opaque Diplomat types with a single field
///
/// This is invoked as `#[diplomat::transparent_convert]`
/// on an opaque Diplomat type. It will add `#[repr(transparent)]` and implement `pub(crate) fn transparent_convert()`
/// which allows constructing an `&Self` from a reference to the inner field.
#[proc_macro_attribute]
pub fn transparent_convert(
_attr: proc_macro::TokenStream,
input: proc_macro::TokenStream,
) -> proc_macro::TokenStream {
// proc macros handle compile errors by using special error tokens.
// In case of an error, we don't want the original code to go away too
// (otherwise that will cause more errors) so we hold on to it and we tack it in
// with no modifications below
let input_cached: proc_macro2::TokenStream = input.clone().into();
let expanded = transparent_convert::gen_transparent_convert(parse_macro_input!(input));
let full = quote! {
#expanded
#input_cached
};
proc_macro::TokenStream::from(full.to_token_stream())
}
#[cfg(test)]
mod tests {
use std::fs::File;
use std::io::{Read, Write};
use std::process::Command;
use quote::ToTokens;
use syn::parse_quote;
use tempfile::tempdir;
use super::gen_bridge;
fn rustfmt_code(code: &str) -> String {
let dir = tempdir().unwrap();
let file_path = dir.path().join("temp.rs");
let mut file = File::create(file_path.clone()).unwrap();
writeln!(file, "{code}").unwrap();
drop(file);
Command::new("rustfmt")
.arg(file_path.to_str().unwrap())
.spawn()
.unwrap()
.wait()
.unwrap();
let mut file = File::open(file_path).unwrap();
let mut data = String::new();
file.read_to_string(&mut data).unwrap();
drop(file);
dir.close().unwrap();
data
}
#[test]
fn method_taking_str() {
insta::assert_snapshot!(rustfmt_code(
&gen_bridge(parse_quote! {
mod ffi {
struct Foo {}
impl Foo {
pub fn from_str(s: &DiplomatStr) {
unimplemented!()
}
}
}
})
.to_token_stream()
.to_string()
));
}
#[test]
fn method_taking_slice() {
insta::assert_snapshot!(rustfmt_code(
&gen_bridge(parse_quote! {
mod ffi {
struct Foo {}
impl Foo {
pub fn from_slice(s: &[f64]) {
unimplemented!()
}
}
}
})
.to_token_stream()
.to_string()
));
}
#[test]
fn method_taking_mutable_slice() {
insta::assert_snapshot!(rustfmt_code(
&gen_bridge(parse_quote! {
mod ffi {
struct Foo {}
impl Foo {
pub fn fill_slice(s: &mut [f64]) {
unimplemented!()
}
}
}
})
.to_token_stream()
.to_string()
));
}
#[test]
fn method_taking_owned_slice() {
insta::assert_snapshot!(rustfmt_code(
&gen_bridge(parse_quote! {
mod ffi {
struct Foo {}
impl Foo {
pub fn fill_slice(s: Box<[u16]>) {
unimplemented!()
}
}
}
})
.to_token_stream()
.to_string()
));
}
#[test]
fn method_taking_owned_str() {
insta::assert_snapshot!(rustfmt_code(
&gen_bridge(parse_quote! {
mod ffi {
struct Foo {}
impl Foo {
pub fn something_with_str(s: Box<str>) {
unimplemented!()
}
}
}
})
.to_token_stream()
.to_string()
));
}
#[test]
fn mod_with_enum() {
insta::assert_snapshot!(rustfmt_code(
&gen_bridge(parse_quote! {
mod ffi {
enum Abc {
A,
B = 123,
}
impl Abc {
pub fn do_something(&self) {
unimplemented!()
}
}
}
})
.to_token_stream()
.to_string()
));
}
#[test]
fn mod_with_writeable_result() {
insta::assert_snapshot!(rustfmt_code(
&gen_bridge(parse_quote! {
mod ffi {
struct Foo {}
impl Foo {
pub fn to_string(&self, to: &mut DiplomatWriteable) -> Result<(), ()> {
unimplemented!()
}
}
}
})
.to_token_stream()
.to_string()
));
}
#[test]
fn mod_with_rust_result() {
insta::assert_snapshot!(rustfmt_code(
&gen_bridge(parse_quote! {
mod ffi {
struct Foo {}
impl Foo {
pub fn bar(&self) -> Result<(), ()> {
unimplemented!()
}
}
}
})
.to_token_stream()
.to_string()
));
}
#[test]
fn multilevel_borrows() {
insta::assert_snapshot!(rustfmt_code(
&gen_bridge(parse_quote! {
mod ffi {
#[diplomat::opaque]
struct Foo<'a>(&'a str);
#[diplomat::opaque]
struct Bar<'b, 'a: 'b>(&'b Foo<'a>);
struct Baz<'x, 'y> {
foo: &'y Foo<'x>,
}
impl<'a> Foo<'a> {
pub fn new(x: &'a str) -> Box<Foo<'a>> {
unimplemented!()
}
pub fn get_bar<'b>(&'b self) -> Box<Bar<'b, 'a>> {
unimplemented!()
}
pub fn get_baz<'b>(&'b self) -> Baz<'b, 'a> {
Bax { foo: self }
}
}
}
})
.to_token_stream()
.to_string()
));
}
#[test]
fn self_params() {
insta::assert_snapshot!(rustfmt_code(
&gen_bridge(parse_quote! {
mod ffi {
#[diplomat::opaque]
struct RefList<'a> {
data: &'a i32,
next: Option<Box<Self>>,
}
impl<'b> RefList<'b> {
pub fn extend(&mut self, other: &Self) -> Self {
unimplemented!()
}
}
}
})
.to_token_stream()
.to_string()
));
}
#[test]
fn cfged_method() {
insta::assert_snapshot!(rustfmt_code(
&gen_bridge(parse_quote! {
mod ffi {
struct Foo {}
impl Foo {
#[cfg(feature = "foo")]
pub fn bar(s: u8) {
unimplemented!()
}
}
}
})
.to_token_stream()
.to_string()
));
insta::assert_snapshot!(rustfmt_code(
&gen_bridge(parse_quote! {
mod ffi {
struct Foo {}
#[cfg(feature = "bar")]
impl Foo {
#[cfg(feature = "foo")]
pub fn bar(s: u8) {
unimplemented!()
}
}
}
})
.to_token_stream()
.to_string()
));
}
#[test]
fn cfgd_struct() {
insta::assert_snapshot!(rustfmt_code(
&gen_bridge(parse_quote! {
mod ffi {
#[diplomat::opaque]
#[cfg(feature = "foo")]
struct Foo {}
#[cfg(feature = "foo")]
impl Foo {
pub fn bar(s: u8) {
unimplemented!()
}
}
}
})
.to_token_stream()
.to_string()
));
}
}