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Replace several linked variables with enumeration for structs
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@Mingun
Mingun committed May 6, 2023
1 parent 5fca5b4 commit fa0dbce
Showing 1 changed file with 75 additions and 65 deletions.
140 changes: 75 additions & 65 deletions serde_derive/src/de.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -289,7 +289,7 @@ fn deserialize_body(cont: &Container, params: &Parameters) -> Fragment {
match &cont.data {
Data::Enum(variants) => deserialize_enum(params, variants, &cont.attrs),
Data::Struct(Style::Struct, fields) => {
deserialize_struct(None, params, fields, &cont.attrs, None, false)
deserialize_struct(params, fields, &cont.attrs, StructForm::Struct)
}
Data::Struct(Style::Tuple, fields) | Data::Struct(Style::Newtype, fields) => {
deserialize_tuple(None, params, fields, &cont.attrs, None)
Expand Down Expand Up @@ -895,13 +895,23 @@ fn deserialize_newtype_struct_in_place(params: &Parameters, field: &Field) -> To
}
}

fn deserialize_struct(
variant_ident: Option<&syn::Ident>,
enum StructForm<'a> {
Struct,
/// Contains a variant name
ExternallyTagged(&'a syn::Ident),
/// Contains a variant name and an intermediate deserializer from which actual
/// deserialization will be performed
InternallyTagged(&'a syn::Ident, TokenStream),
/// Contains a variant name and an intermediate deserializer from which actual
/// deserialization will be performed
Untagged(&'a syn::Ident, TokenStream),
}

fn deserialize_struct<'a>(
params: &Parameters,
fields: &[Field],
cattrs: &attr::Container,
deserializer: Option<TokenStream>,
untagged: bool,
form: StructForm<'a>,
) -> Fragment {
let this_type = &params.this_type;
let this_value = &params.this_value;
Expand All @@ -919,13 +929,19 @@ fn deserialize_struct(
quote!(#this_value)
};

let type_path = match variant_ident {
Some(variant_ident) => quote!(#construct::#variant_ident),
None => construct,
let type_path = match form {
StructForm::Struct => construct,
StructForm::ExternallyTagged(variant_ident)
| StructForm::InternallyTagged(variant_ident, _)
| StructForm::Untagged(variant_ident, _) => quote!(#construct::#variant_ident),
};
let expecting = match variant_ident {
Some(variant_ident) => format!("struct variant {}::{}", params.type_name(), variant_ident),
None => format!("struct {}", params.type_name()),
let expecting = match form {
StructForm::Struct => format!("struct {}", params.type_name()),
StructForm::ExternallyTagged(variant_ident)
| StructForm::InternallyTagged(variant_ident, _)
| StructForm::Untagged(variant_ident, _) => {
format!("struct variant {}::{}", params.type_name(), variant_ident)
}
};
let expecting = cattrs.expecting().unwrap_or(&expecting);

Expand All @@ -952,35 +968,35 @@ fn deserialize_struct(

// untagged struct variants do not get a visit_seq method. The same applies to
// structs that only have a map representation.
let visit_seq = if untagged || cattrs.has_flatten() {
None
} else {
let mut_seq = if field_names_idents.is_empty() {
quote!(_)
} else {
quote!(mut __seq)
};
let visit_seq = match form {
StructForm::Untagged(..) => None,
_ if cattrs.has_flatten() => None,
_ => {
let mut_seq = if field_names_idents.is_empty() {
quote!(_)
} else {
quote!(mut __seq)
};

let visit_seq = Stmts(deserialize_seq(
&type_path, params, fields, true, cattrs, expecting,
));
let visit_seq = Stmts(deserialize_seq(
&type_path, params, fields, true, cattrs, expecting,
));

Some(quote! {
#[inline]
fn visit_seq<__A>(self, #mut_seq: __A) -> _serde::__private::Result<Self::Value, __A::Error>
where
__A: _serde::de::SeqAccess<#delife>,
{
#visit_seq
}
})
Some(quote! {
#[inline]
fn visit_seq<__A>(self, #mut_seq: __A) -> _serde::__private::Result<Self::Value, __A::Error>
where
__A: _serde::de::SeqAccess<#delife>,
{
#visit_seq
}
})
}
};
let visit_map = Stmts(deserialize_map(&type_path, params, fields, cattrs));

let is_enum = variant_ident.is_some();
let need_seed = deserializer.is_none();
let visitor_seed = if need_seed && is_enum && cattrs.has_flatten() {
Some(quote! {
let visitor_seed = match form {
StructForm::ExternallyTagged(..) if cattrs.has_flatten() => Some(quote! {
impl #de_impl_generics _serde::de::DeserializeSeed<#delife> for __Visitor #de_ty_generics #where_clause {
type Value = #this_type #ty_generics;

Expand All @@ -991,9 +1007,8 @@ fn deserialize_struct(
_serde::Deserializer::deserialize_map(__deserializer, self)
}
}
})
} else {
None
}),
_ => None,
};

let fields_stmt = if cattrs.has_flatten() {
Expand All @@ -1015,27 +1030,28 @@ fn deserialize_struct(
lifetime: _serde::__private::PhantomData,
}
};
let dispatch = if let Some(deserializer) = deserializer {
quote! {
_serde::Deserializer::deserialize_any(#deserializer, #visitor_expr)
let dispatch = match form {
StructForm::Struct if cattrs.has_flatten() => quote! {
_serde::Deserializer::deserialize_map(__deserializer, #visitor_expr)
},
StructForm::Struct => {
let type_name = cattrs.name().deserialize_name();
quote! {
_serde::Deserializer::deserialize_struct(__deserializer, #type_name, FIELDS, #visitor_expr)
}
}
} else if is_enum && cattrs.has_flatten() {
quote! {
StructForm::ExternallyTagged(_) if cattrs.has_flatten() => quote! {
_serde::de::VariantAccess::newtype_variant_seed(__variant, #visitor_expr)
}
} else if is_enum {
quote! {
},
StructForm::ExternallyTagged(_) => quote! {
_serde::de::VariantAccess::struct_variant(__variant, FIELDS, #visitor_expr)
}
} else if cattrs.has_flatten() {
quote! {
_serde::Deserializer::deserialize_map(__deserializer, #visitor_expr)
}
} else {
let type_name = cattrs.name().deserialize_name();
quote! {
_serde::Deserializer::deserialize_struct(__deserializer, #type_name, FIELDS, #visitor_expr)
}
},
StructForm::InternallyTagged(_, deserializer) => quote! {
_serde::Deserializer::deserialize_any(#deserializer, #visitor_expr)
},
StructForm::Untagged(_, deserializer) => quote! {
_serde::Deserializer::deserialize_any(#deserializer, #visitor_expr)
},
};

quote_block! {
Expand Down Expand Up @@ -1762,12 +1778,10 @@ fn deserialize_externally_tagged_variant(
deserialize_tuple(Some(variant_ident), params, &variant.fields, cattrs, None)
}
Style::Struct => deserialize_struct(
Some(variant_ident),
params,
&variant.fields,
cattrs,
None,
false,
StructForm::ExternallyTagged(variant_ident),
),
}
}
Expand Down Expand Up @@ -1807,12 +1821,10 @@ fn deserialize_internally_tagged_variant(
&deserializer,
),
Style::Struct => deserialize_struct(
Some(variant_ident),
params,
&variant.fields,
cattrs,
Some(deserializer),
false,
StructForm::InternallyTagged(variant_ident, deserializer),
),
Style::Tuple => unreachable!("checked in serde_derive_internals"),
}
Expand Down Expand Up @@ -1866,12 +1878,10 @@ fn deserialize_untagged_variant(
Some(deserializer),
),
Style::Struct => deserialize_struct(
Some(variant_ident),
params,
&variant.fields,
cattrs,
Some(deserializer),
true,
StructForm::Untagged(variant_ident, deserializer),
),
}
}
Expand Down

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