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use proc_macro2::{Ident, Span, TokenStream};
use quote::quote;
use syn::{
parse::ParseStream, spanned::Spanned, Attribute, Data, DataEnum, DeriveInput, Expr, Index, Lit,
Variant,
};
use crate::{
ffiops,
util::{
create_metadata_items, either_attribute_arg, extract_docstring, ident_to_string, kw,
mod_path, try_metadata_value_from_usize, try_read_field, AttributeSliceExt,
UniffiAttributeArgs,
},
DeriveOptions,
};
use uniffi_meta::EnumShape;
/// Stores parsed data from the Derive Input for the enum.
pub struct EnumItem {
ident: Ident,
enum_: DataEnum,
docstring: String,
discr_type: Option<Ident>,
non_exhaustive: bool,
attr: EnumAttr,
}
impl EnumItem {
pub fn new(input: DeriveInput) -> syn::Result<Self> {
let enum_ = match input.data {
Data::Enum(e) => e,
_ => {
return Err(syn::Error::new(
Span::call_site(),
"This derive must only be used on enums",
))
}
};
Ok(Self {
enum_,
ident: input.ident,
docstring: extract_docstring(&input.attrs)?,
discr_type: Self::extract_repr(&input.attrs)?,
non_exhaustive: Self::extract_non_exhaustive(&input.attrs),
attr: input.attrs.parse_uniffi_attr_args()?,
})
}
pub fn extract_repr(attrs: &[Attribute]) -> syn::Result<Option<Ident>> {
let mut result = None;
for attr in attrs {
if attr.path().is_ident("repr") {
attr.parse_nested_meta(|meta| {
result = match meta.path.get_ident() {
Some(i) => {
let s = i.to_string();
match s.as_str() {
"u8" | "u16" | "u32" | "u64" | "usize" | "i8" | "i16" | "i32"
| "i64" | "isize" => Some(i.clone()),
// while the default repr for an enum is `isize` we don't apply that default here.
_ => None,
}
}
_ => None,
};
Ok(())
})?
}
}
Ok(result)
}
pub fn extract_non_exhaustive(attrs: &[Attribute]) -> bool {
attrs.iter().any(|a| a.path().is_ident("non_exhaustive"))
}
pub fn check_attributes_valid_for_enum(&self) -> syn::Result<()> {
if let Some(flat_error) = &self.attr.flat_error {
return Err(syn::Error::new(
flat_error.span(),
"flat_error not allowed for non-error enums",
));
}
if let Some(with_try_read) = &self.attr.with_try_read {
return Err(syn::Error::new(
with_try_read.span(),
"with_try_read not allowed for non-error enums",
));
}
Ok(())
}
pub fn ident(&self) -> &Ident {
&self.ident
}
pub fn enum_(&self) -> &DataEnum {
&self.enum_
}
pub fn is_non_exhaustive(&self) -> bool {
self.non_exhaustive
}
pub fn docstring(&self) -> &str {
self.docstring.as_str()
}
pub fn discr_type(&self) -> Option<&Ident> {
self.discr_type.as_ref()
}
pub fn name(&self) -> String {
ident_to_string(&self.ident)
}
pub fn is_flat_error(&self) -> bool {
self.attr.flat_error.is_some()
}
pub fn generate_error_try_read(&self) -> bool {
self.attr.with_try_read.is_some()
}
}
pub fn expand_enum(input: DeriveInput, options: DeriveOptions) -> syn::Result<TokenStream> {
let item = EnumItem::new(input)?;
item.check_attributes_valid_for_enum()?;
let ffi_converter_impl = enum_ffi_converter_impl(&item, &options);
let meta_static_var = options
.generate_metadata
.then(|| enum_meta_static_var(&item).unwrap_or_else(syn::Error::into_compile_error));
Ok(quote! {
#ffi_converter_impl
#meta_static_var
})
}
pub(crate) fn enum_ffi_converter_impl(item: &EnumItem, options: &DeriveOptions) -> TokenStream {
enum_or_error_ffi_converter_impl(
item,
options,
quote! { ::uniffi::metadata::codes::TYPE_ENUM },
)
}
pub(crate) fn rich_error_ffi_converter_impl(
item: &EnumItem,
options: &DeriveOptions,
) -> TokenStream {
enum_or_error_ffi_converter_impl(
item,
options,
quote! { ::uniffi::metadata::codes::TYPE_ENUM },
)
}
fn enum_or_error_ffi_converter_impl(
item: &EnumItem,
options: &DeriveOptions,
metadata_type_code: TokenStream,
) -> TokenStream {
let name = item.name();
let ident = item.ident();
let impl_spec = options.ffi_impl_header("FfiConverter", ident);
let derive_ffi_traits = options.derive_all_ffi_traits(ident);
let mod_path = match mod_path() {
Ok(p) => p,
Err(e) => return e.into_compile_error(),
};
let mut write_match_arms: Vec<_> = item
.enum_()
.variants
.iter()
.enumerate()
.map(|(i, v)| {
let v_ident = &v.ident;
let field_idents = v
.fields
.iter()
.enumerate()
.map(|(i, f)| {
f.ident
.clone()
.unwrap_or_else(|| Ident::new(&format!("e{i}"), f.span()))
})
.collect::<Vec<Ident>>();
let idx = Index::from(i + 1);
let write_fields =
std::iter::zip(v.fields.iter(), field_idents.iter()).map(|(f, ident)| {
let write = ffiops::write(&f.ty);
quote! { #write(#ident, buf); }
});
let is_tuple = v.fields.iter().any(|f| f.ident.is_none());
let fields = if is_tuple {
quote! { ( #(#field_idents),* ) }
} else {
quote! { { #(#field_idents),* } }
};
quote! {
Self::#v_ident #fields => {
::uniffi::deps::bytes::BufMut::put_i32(buf, #idx);
#(#write_fields)*
}
}
})
.collect();
if item.is_non_exhaustive() {
write_match_arms.push(quote! {
_ => ::std::panic!("Unexpected variant in non-exhaustive enum"),
})
}
let write_impl = quote! {
match obj { #(#write_match_arms)* }
};
let try_read_match_arms = item.enum_().variants.iter().enumerate().map(|(i, v)| {
let idx = Index::from(i + 1);
let v_ident = &v.ident;
let is_tuple = v.fields.iter().any(|f| f.ident.is_none());
let try_read_fields = v.fields.iter().map(try_read_field);
if is_tuple {
quote! {
#idx => Self::#v_ident ( #(#try_read_fields)* ),
}
} else {
quote! {
#idx => Self::#v_ident { #(#try_read_fields)* },
}
}
});
let error_format_string = format!("Invalid {name} enum value: {{}}");
let try_read_impl = quote! {
::uniffi::check_remaining(buf, 4)?;
::std::result::Result::Ok(match ::uniffi::deps::bytes::Buf::get_i32(buf) {
#(#try_read_match_arms)*
v => ::uniffi::deps::anyhow::bail!(#error_format_string, v),
})
};
quote! {
#[automatically_derived]
unsafe #impl_spec {
::uniffi::ffi_converter_rust_buffer_lift_and_lower!(crate::UniFfiTag);
fn write(obj: Self, buf: &mut ::std::vec::Vec<u8>) {
#write_impl
}
fn try_read(buf: &mut &[::std::primitive::u8]) -> ::uniffi::deps::anyhow::Result<Self> {
#try_read_impl
}
const TYPE_ID_META: ::uniffi::MetadataBuffer = ::uniffi::MetadataBuffer::from_code(#metadata_type_code)
.concat_str(#mod_path)
.concat_str(#name);
}
#derive_ffi_traits
}
}
pub(crate) fn enum_meta_static_var(item: &EnumItem) -> syn::Result<TokenStream> {
let name = item.name();
let module_path = mod_path()?;
let non_exhaustive = item.is_non_exhaustive();
let docstring = item.docstring();
let shape = EnumShape::Enum.as_u8();
let mut metadata_expr = quote! {
::uniffi::MetadataBuffer::from_code(::uniffi::metadata::codes::ENUM)
.concat_str(#module_path)
.concat_str(#name)
.concat_value(#shape)
};
metadata_expr.extend(match item.discr_type() {
None => quote! { .concat_bool(false) },
Some(t) => {
let type_id_meta = ffiops::type_id_meta(t);
quote! { .concat_bool(true).concat(#type_id_meta) }
}
});
metadata_expr.extend(variant_metadata(item)?);
metadata_expr.extend(quote! {
.concat_bool(#non_exhaustive)
.concat_long_str(#docstring)
});
Ok(create_metadata_items("enum", &name, metadata_expr, None))
}
fn variant_value(v: &Variant) -> syn::Result<TokenStream> {
let Some((_, e)) = &v.discriminant else {
return Ok(quote! { .concat_bool(false) });
};
// Attempting to expose an enum value which we don't understand is a hard-error
// rather than silently ignoring it. If we had the ability to emit a warning that
// might make more sense.
// We can't sanely handle most expressions other than literals, but we can handle
// negative literals.
let mut negate = false;
let lit = match e {
Expr::Lit(lit) => lit,
Expr::Unary(expr_unary) if matches!(expr_unary.op, syn::UnOp::Neg(_)) => {
negate = true;
match *expr_unary.expr {
Expr::Lit(ref lit) => lit,
_ => {
return Err(syn::Error::new_spanned(
e,
"UniFFI disciminant values must be a literal",
));
}
}
}
_ => {
return Err(syn::Error::new_spanned(
e,
"UniFFI disciminant values must be a literal",
));
}
};
let Lit::Int(ref intlit) = lit.lit else {
return Err(syn::Error::new_spanned(
v,
"UniFFI disciminant values must be a literal integer",
));
};
if !intlit.suffix().is_empty() {
return Err(syn::Error::new_spanned(
intlit,
"integer literals with suffix not supported by UniFFI here",
));
}
let digits = if negate {
format!("-{}", intlit.base10_digits())
} else {
intlit.base10_digits().to_string()
};
Ok(quote! {
.concat_bool(true)
.concat_value(::uniffi::metadata::codes::LIT_INT)
.concat_str(#digits)
})
}
pub fn variant_metadata(item: &EnumItem) -> syn::Result<Vec<TokenStream>> {
let enum_ = item.enum_();
let variants_len =
try_metadata_value_from_usize(enum_.variants.len(), "UniFFI limits enums to 256 variants")?;
std::iter::once(Ok(quote! { .concat_value(#variants_len) }))
.chain(enum_.variants.iter().map(|v| {
let fields_len = try_metadata_value_from_usize(
v.fields.len(),
"UniFFI limits enum variants to 256 fields",
)?;
let field_names = v
.fields
.iter()
.map(|f| f.ident.as_ref().map(ident_to_string).unwrap_or_default())
.collect::<Vec<_>>();
let name = ident_to_string(&v.ident);
let value_tokens = variant_value(v)?;
let docstring = extract_docstring(&v.attrs)?;
let field_docstrings = v
.fields
.iter()
.map(|f| extract_docstring(&f.attrs))
.collect::<syn::Result<Vec<_>>>()?;
let field_type_id_metas = v.fields.iter().map(|f| ffiops::type_id_meta(&f.ty));
Ok(quote! {
.concat_str(#name)
#value_tokens
.concat_value(#fields_len)
#(
.concat_str(#field_names)
.concat(#field_type_id_metas)
// field defaults not yet supported for enums
.concat_bool(false)
.concat_long_str(#field_docstrings)
)*
.concat_long_str(#docstring)
})
}))
.collect()
}
/// Handle #[uniffi(...)] attributes for enums
#[derive(Clone, Default)]
pub struct EnumAttr {
// All of these attributes are only relevant for errors, but they're defined here so that we
// can reuse EnumItem for errors.
pub flat_error: Option<kw::flat_error>,
pub with_try_read: Option<kw::with_try_read>,
}
impl UniffiAttributeArgs for EnumAttr {
fn parse_one(input: ParseStream<'_>) -> syn::Result<Self> {
let lookahead = input.lookahead1();
if lookahead.peek(kw::flat_error) {
Ok(Self {
flat_error: input.parse()?,
..Self::default()
})
} else if lookahead.peek(kw::with_try_read) {
Ok(Self {
with_try_read: input.parse()?,
..Self::default()
})
} else if lookahead.peek(kw::handle_unknown_callback_error) {
// Not used anymore, but still allowed
Ok(Self::default())
} else {
Err(lookahead.error())
}
}
fn merge(self, other: Self) -> syn::Result<Self> {
Ok(Self {
flat_error: either_attribute_arg(self.flat_error, other.flat_error)?,
with_try_read: either_attribute_arg(self.with_try_read, other.with_try_read)?,
})
}
}