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|
use proc_macro2::TokenStream;
use quote::{quote, ToTokens};
use crate::ast::{Data, Fields, Style};
use crate::codegen::{Field, OuterFromImpl, TraitImpl, Variant};
pub struct FromMetaImpl<'a> {
pub base: TraitImpl<'a>,
}
impl<'a> ToTokens for FromMetaImpl<'a> {
fn to_tokens(&self, tokens: &mut TokenStream) {
let base = &self.base;
let impl_block = match base.data {
// Unit structs allow empty bodies only.
Data::Struct(ref vd) if vd.style.is_unit() => {
let ty_ident = base.ident;
quote!(
fn from_word() -> ::darling::Result<Self> {
::darling::export::Ok(#ty_ident)
}
)
}
// Newtype structs proxy to the sole value they contain.
Data::Struct(Fields {
ref fields,
style: Style::Tuple,
..
}) if fields.len() == 1 => {
let ty_ident = base.ident;
quote!(
fn from_meta(__item: &::darling::export::syn::Meta) -> ::darling::Result<Self> {
::darling::FromMeta::from_meta(__item)
.map_err(|e| e.with_span(&__item))
.map(#ty_ident)
}
)
}
Data::Struct(Fields {
style: Style::Tuple,
..
}) => {
panic!("Multi-field tuples are not supported");
}
Data::Struct(ref data) => {
let inits = data.fields.iter().map(Field::as_initializer);
let declare_errors = base.declare_errors();
let require_fields = base.require_fields();
let check_errors = base.check_errors();
let decls = base.local_declarations();
let core_loop = base.core_loop();
let default = base.fallback_decl();
let post_transform = base.post_transform_call();
quote!(
fn from_list(__items: &[::darling::export::NestedMeta]) -> ::darling::Result<Self> {
#decls
#declare_errors
#core_loop
#require_fields
#check_errors
#default
::darling::export::Ok(Self {
#(#inits),*
}) #post_transform
}
)
}
Data::Enum(ref variants) => {
let unit_arms = variants.iter().map(Variant::as_unit_match_arm);
let unknown_variant_err = if !variants.is_empty() {
let names = variants.iter().map(Variant::as_name);
quote! {
unknown_field_with_alts(__other, &[#(#names),*])
}
} else {
quote! {
unknown_field(__other)
}
};
let word_or_err = variants
.iter()
.find_map(|variant| {
if variant.word {
let ty_ident = variant.ty_ident;
let variant_ident = variant.variant_ident;
Some(quote!(::darling::export::Ok(#ty_ident::#variant_ident)))
} else {
None
}
})
.unwrap_or_else(|| {
quote!(::darling::export::Err(
::darling::Error::unsupported_format("word")
))
});
quote!(
fn from_list(__outer: &[::darling::export::NestedMeta]) -> ::darling::Result<Self> {
// An enum must have exactly one value inside the parentheses if it's not a unit
// match arm.
match __outer.len() {
0 => ::darling::export::Err(::darling::Error::too_few_items(1)),
1 => {
if let ::darling::export::NestedMeta::Meta(ref __nested) = __outer[0] {
match ::darling::util::path_to_string(__nested.path()).as_ref() {
#(#variants)*
__other => ::darling::export::Err(::darling::Error::#unknown_variant_err.with_span(__nested))
}
} else {
::darling::export::Err(::darling::Error::unsupported_format("literal"))
}
}
_ => ::darling::export::Err(::darling::Error::too_many_items(1)),
}
}
fn from_string(lit: &str) -> ::darling::Result<Self> {
match lit {
#(#unit_arms)*
__other => ::darling::export::Err(::darling::Error::unknown_value(__other))
}
}
fn from_word() -> ::darling::Result<Self> {
#word_or_err
}
)
}
};
self.wrap(impl_block, tokens);
}
}
impl<'a> OuterFromImpl<'a> for FromMetaImpl<'a> {
fn trait_path(&self) -> syn::Path {
path!(::darling::FromMeta)
}
fn base(&'a self) -> &'a TraitImpl<'a> {
&self.base
}
}
|
