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serde_derive: reduce llvm-lines in ser.rs, reuse fn field_i #3038

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098da70
serde_derive: reduce llvm-lines in ser.rs, reuse fn field_i
dishmaker Feb 13, 2026
ea04847
serde_derive: rewrite serialize_struct_visitor
dishmaker Feb 13, 2026
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2 changes: 1 addition & 1 deletion serde_derive/src/de.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -655,7 +655,7 @@ struct FieldWithAliases<'a> {
aliases: &'a BTreeSet<Name>,
}

fn field_i(i: usize) -> Ident {
pub(crate) fn field_i(i: usize) -> Ident {
Ident::new(&format!("__field{}", i), Span::call_site())
}

Expand Down
183 changes: 92 additions & 91 deletions serde_derive/src/ser.rs
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Original file line number Diff line number Diff line change
@@ -1,3 +1,4 @@
use crate::de::field_i;
use crate::deprecated::allow_deprecated;
use crate::fragment::{Fragment, Match, Stmts};
use crate::internals::ast::{Container, Data, Field, Style, Variant};
Expand Down Expand Up @@ -457,8 +458,7 @@ fn serialize_variant(
}
}
Style::Tuple => {
let field_names = (0..variant.fields.len())
.map(|i| Ident::new(&format!("__field{}", i), Span::call_site()));
let field_names = (0..variant.fields.len()).map(|i| field_i(i));
quote! {
#this_value::#variant_ident(#(ref #field_names),*)
}
Expand Down Expand Up @@ -713,9 +713,9 @@ fn serialize_adjacently_tagged_variant(
unreachable!()
}
}
Style::Newtype => vec![Member::Named(Ident::new("__field0", Span::call_site()))],
Style::Newtype => vec![Member::Named(field_i(0))],
Style::Tuple => (0..variant.fields.len())
.map(|i| Member::Named(Ident::new(&format!("__field{}", i), Span::call_site())))
.map(|i| Member::Named(field_i(i)))
.collect(),
Style::Struct => variant.fields.iter().map(|f| f.member.clone()).collect(),
};
Expand Down Expand Up @@ -834,7 +834,7 @@ fn serialize_tuple_variant(
.map(|(i, field)| match field.attrs.skip_serializing_if() {
None => quote!(1),
Some(path) => {
let field_expr = Ident::new(&format!("__field{}", i), Span::call_site());
let field_expr = field_i(i);
quote!(if #path(#field_expr) { 0 } else { 1 })
}
})
Expand Down Expand Up @@ -1059,46 +1059,47 @@ fn serialize_tuple_struct_visitor(
is_enum: bool,
tuple_trait: &TupleTrait,
) -> Vec<TokenStream> {
fields
.iter()
.enumerate()
.filter(|(_, field)| !field.attrs.skip_serializing())
.map(|(i, field)| {
let mut field_expr = if is_enum {
let id = Ident::new(&format!("__field{}", i), Span::call_site());
quote!(#id)
} else {
get_member(
params,
field,
&Member::Unnamed(Index {
index: i as u32,
span: Span::call_site(),
}),
)
};
let mut dst_fields = Vec::new();

for (i, field) in fields.iter().enumerate() {
if field.attrs.skip_serializing() {
continue;
}
let mut field_expr = if is_enum {
let id = field_i(i);
quote!(#id)
} else {
get_member(
params,
field,
&Member::Unnamed(Index {
index: i as u32,
span: Span::call_site(),
}),
)
};

let skip = field
.attrs
.skip_serializing_if()
.map(|path| quote!(#path(#field_expr)));
let skip = field
.attrs
.skip_serializing_if()
.map(|path| quote!(#path(#field_expr)));

if let Some(path) = field.attrs.serialize_with() {
field_expr = wrap_serialize_field_with(params, field.ty, path, &field_expr);
}
if let Some(path) = field.attrs.serialize_with() {
field_expr = wrap_serialize_field_with(params, field.ty, path, &field_expr);
}

let span = field.original.span();
let func = tuple_trait.serialize_element(span);
let ser = quote! {
#func(&mut __serde_state, #field_expr)?;
};
let span = field.original.span();
let func = tuple_trait.serialize_element(span);
let ser = quote! {
#func(&mut __serde_state, #field_expr)?;
};

match skip {
None => ser,
Some(skip) => quote!(if !#skip { #ser }),
}
})
.collect()
dst_fields.push(match skip {
None => ser,
Some(skip) => quote!(if !#skip { #ser }),
});
}
dst_fields
}

fn serialize_struct_visitor(
Expand All @@ -1107,64 +1108,66 @@ fn serialize_struct_visitor(
is_enum: bool,
struct_trait: &StructTrait,
) -> Vec<TokenStream> {
fields
.iter()
.filter(|&field| !field.attrs.skip_serializing())
.map(|field| {
let member = &field.member;
let mut dst_fields = Vec::new();

let mut field_expr = if is_enum {
quote!(#member)
} else {
get_member(params, field, member)
};
for field in fields {
if field.attrs.skip_serializing() {
continue;
}
let member = &field.member;

let key_expr = field.attrs.name().serialize_name();
let mut field_expr = if is_enum {
quote!(#member)
} else {
get_member(params, field, member)
};

let skip = field
.attrs
.skip_serializing_if()
.map(|path| quote!(#path(#field_expr)));
let key_expr = field.attrs.name().serialize_name();

if let Some(path) = field.attrs.serialize_with() {
field_expr = wrap_serialize_field_with(params, field.ty, path, &field_expr);
}
let skip = field
.attrs
.skip_serializing_if()
.map(|path| quote!(#path(#field_expr)));

let span = field.original.span();
let ser = if field.attrs.flatten() {
let func = quote_spanned!(span=> _serde::Serialize::serialize);
quote! {
#func(&#field_expr, _serde::#private::ser::FlatMapSerializer(&mut __serde_state))?;
}
} else {
let func = struct_trait.serialize_field(span);
quote! {
#func(&mut __serde_state, #key_expr, #field_expr)?;
}
};
if let Some(path) = field.attrs.serialize_with() {
field_expr = wrap_serialize_field_with(params, field.ty, path, &field_expr);
}

match skip {
None => ser,
Some(skip) => {
if let Some(skip_func) = struct_trait.skip_field(span) {
quote! {
if !#skip {
#ser
} else {
#skip_func(&mut __serde_state, #key_expr)?;
}
let span = field.original.span();
let ser = if field.attrs.flatten() {
let func = quote_spanned!(span=> _serde::Serialize::serialize);
quote! {
#func(&#field_expr, _serde::#private::ser::FlatMapSerializer(&mut __serde_state))?;
}
} else {
let func = struct_trait.serialize_field(span);
quote! {
#func(&mut __serde_state, #key_expr, #field_expr)?;
}
};

dst_fields.push(match skip {
None => ser,
Some(skip) => {
if let Some(skip_func) = struct_trait.skip_field(span) {
quote! {
if !#skip {
#ser
} else {
#skip_func(&mut __serde_state, #key_expr)?;
}
} else {
quote! {
if !#skip {
#ser
}
}
} else {
quote! {
if !#skip {
#ser
}
}
}
}
})
.collect()
});
}
dst_fields
}

fn wrap_serialize_field_with(
Expand All @@ -1188,9 +1191,7 @@ fn wrap_serialize_variant_with(
.map(|field| {
let id = match &field.member {
Member::Named(ident) => ident.clone(),
Member::Unnamed(member) => {
Ident::new(&format!("__field{}", member.index), Span::call_site())
}
Member::Unnamed(member) => field_i(member.index as usize),
};
quote!(#id)
})
Expand Down