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use crate::de::enum_adjacently;
use crate::de::enum_externally;
use crate::de::enum_internally;
use crate::de::enum_untagged;
use crate::de::identifier;
use crate::de::{field_i, FieldWithAliases, Parameters};
use crate::fragment::{Expr, Fragment, Stmts};
use crate::internals::ast::Variant;
use crate::internals::attr;
use crate::private;
use proc_macro2::TokenStream;
use quote::quote;
/// Generates `Deserialize::deserialize` body for an `enum Enum {...}`
pub(super) fn deserialize(
params: &Parameters,
variants: &[Variant],
cattrs: &attr::Container,
) -> Fragment {
// The variants have already been checked (in ast.rs) that all untagged variants appear at the end
match variants.iter().position(|var| var.attrs.untagged()) {
Some(variant_idx) => {
let (tagged, untagged) = variants.split_at(variant_idx);
let tagged_frag = Expr(deserialize_homogeneous_enum(params, tagged, cattrs));
// Ignore any error associated with non-untagged deserialization so that we
// can fall through to the untagged variants. This may be infallible so we
// need to provide the error type.
let first_attempt = quote! {
if let _serde::#private::Result::<_, __D::Error>::Ok(__ok) = (|| #tagged_frag)() {
return _serde::#private::Ok(__ok);
}
};
enum_untagged::deserialize(params, untagged, cattrs, Some(first_attempt))
}
None => deserialize_homogeneous_enum(params, variants, cattrs),
}
}
fn deserialize_homogeneous_enum(
params: &Parameters,
variants: &[Variant],
cattrs: &attr::Container,
) -> Fragment {
match cattrs.tag() {
attr::TagType::External => enum_externally::deserialize(params, variants, cattrs),
attr::TagType::Internal { tag } => {
enum_internally::deserialize(params, variants, cattrs, tag)
}
attr::TagType::Adjacent { tag, content } => {
enum_adjacently::deserialize(params, variants, cattrs, tag, content)
}
attr::TagType::None => enum_untagged::deserialize(params, variants, cattrs, None),
}
}
pub fn prepare_enum_variant_enum(variants: &[Variant]) -> (TokenStream, Stmts) {
let deserialized_variants = variants
.iter()
.enumerate()
.filter(|&(_i, variant)| !variant.attrs.skip_deserializing());
let fallthrough = deserialized_variants
.clone()
.find(|(_i, variant)| variant.attrs.other())
.map(|(i, _variant)| {
let ignore_variant = field_i(i);
quote!(_serde::#private::Ok(__Field::#ignore_variant))
});
let variants_stmt = {
let variant_names = deserialized_variants
.clone()
.flat_map(|(_i, variant)| variant.attrs.aliases());
quote! {
#[doc(hidden)]
const VARIANTS: &'static [&'static str] = &[ #(#variant_names),* ];
}
};
let deserialized_variants: Vec<_> = deserialized_variants
.map(|(i, variant)| FieldWithAliases {
ident: field_i(i),
aliases: variant.attrs.aliases(),
})
.collect();
let variant_visitor = Stmts(identifier::deserialize_generated(
&deserialized_variants,
false, // variant identifiers do not depend on the presence of flatten fields
true,
None,
fallthrough,
));
(variants_stmt, variant_visitor)
}