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//! A Serde ast, parsed from the Syn ast and ready to generate Rust code.
use crate::internals::{attr, check, Ctxt, Derive};
use syn::punctuated::Punctuated;
use syn::Token;
/// A source data structure annotated with `#[derive(Serialize)]` and/or `#[derive(Deserialize)]`,
/// parsed into an internal representation.
pub struct Container<'a> {
/// The struct or enum name (without generics).
pub ident: syn::Ident,
/// Attributes on the structure, parsed for Serde.
pub attrs: attr::Container,
/// The contents of the struct or enum.
pub data: Data<'a>,
/// Any generics on the struct or enum.
pub generics: &'a syn::Generics,
/// Original input.
pub original: &'a syn::DeriveInput,
}
/// The fields of a struct or enum.
///
/// Analogous to `syn::Data`.
pub enum Data<'a> {
Enum(Vec<Variant<'a>>),
Struct(Style, Vec<Field<'a>>),
}
/// A variant of an enum.
pub struct Variant<'a> {
pub ident: syn::Ident,
pub attrs: attr::Variant,
pub style: Style,
pub fields: Vec<Field<'a>>,
pub original: &'a syn::Variant,
}
/// A field of a struct.
pub struct Field<'a> {
pub member: syn::Member,
pub attrs: attr::Field,
pub ty: &'a syn::Type,
pub original: &'a syn::Field,
}
#[derive(Copy, Clone)]
pub enum Style {
/// Named fields.
Struct,
/// Many unnamed fields.
Tuple,
/// One unnamed field.
Newtype,
/// No fields.
Unit,
}
impl<'a> Container<'a> {
/// Convert the raw Syn ast into a parsed container object, collecting errors in `cx`.
pub fn from_ast(
cx: &Ctxt,
item: &'a syn::DeriveInput,
derive: Derive,
) -> Option<Container<'a>> {
let mut attrs = attr::Container::from_ast(cx, item);
let mut data = match &item.data {
syn::Data::Enum(data) => Data::Enum(enum_from_ast(cx, &data.variants, attrs.default())),
syn::Data::Struct(data) => {
let (style, fields) = struct_from_ast(cx, &data.fields, None, attrs.default());
Data::Struct(style, fields)
}
syn::Data::Union(_) => {
cx.error_spanned_by(item, "Serde does not support derive for unions");
return None;
}
};
let mut has_flatten = false;
match &mut data {
Data::Enum(variants) => {
for variant in variants {
variant.attrs.rename_by_rules(attrs.rename_all_rules());
for field in &mut variant.fields {
if field.attrs.flatten() {
has_flatten = true;
}
field.attrs.rename_by_rules(
variant
.attrs
.rename_all_rules()
.or(attrs.rename_all_fields_rules()),
);
}
}
}
Data::Struct(_, fields) => {
for field in fields {
if field.attrs.flatten() {
has_flatten = true;
}
field.attrs.rename_by_rules(attrs.rename_all_rules());
}
}
}
if has_flatten {
attrs.mark_has_flatten();
}
let mut item = Container {
ident: item.ident.clone(),
attrs,
data,
generics: &item.generics,
original: item,
};
check::check(cx, &mut item, derive);
Some(item)
}
}
impl<'a> Data<'a> {
pub fn all_fields(&'a self) -> Box<dyn Iterator<Item = &'a Field<'a>> + 'a> {
match self {
Data::Enum(variants) => {
Box::new(variants.iter().flat_map(|variant| variant.fields.iter()))
}
Data::Struct(_, fields) => Box::new(fields.iter()),
}
}
pub fn has_getter(&self) -> bool {
self.all_fields().any(|f| f.attrs.getter().is_some())
}
}
fn enum_from_ast<'a>(
cx: &Ctxt,
variants: &'a Punctuated<syn::Variant, Token![,]>,
container_default: &attr::Default,
) -> Vec<Variant<'a>> {
let variants: Vec<Variant> = variants
.iter()
.map(|variant| {
let attrs = attr::Variant::from_ast(cx, variant);
let (style, fields) =
struct_from_ast(cx, &variant.fields, Some(&attrs), container_default);
Variant {
ident: variant.ident.clone(),
attrs,
style,
fields,
original: variant,
}
})
.collect();
let index_of_last_tagged_variant = variants
.iter()
.rposition(|variant| !variant.attrs.untagged());
if let Some(index_of_last_tagged_variant) = index_of_last_tagged_variant {
for variant in &variants[..index_of_last_tagged_variant] {
if variant.attrs.untagged() {
cx.error_spanned_by(&variant.ident, "all variants with the #[serde(untagged)] attribute must be placed at the end of the enum");
}
}
}
variants
}
fn struct_from_ast<'a>(
cx: &Ctxt,
fields: &'a syn::Fields,
attrs: Option<&attr::Variant>,
container_default: &attr::Default,
) -> (Style, Vec<Field<'a>>) {
match fields {
syn::Fields::Named(fields) => (
Style::Struct,
fields_from_ast(cx, &fields.named, attrs, container_default),
),
syn::Fields::Unnamed(fields) if fields.unnamed.len() == 1 => (
Style::Newtype,
fields_from_ast(cx, &fields.unnamed, attrs, container_default),
),
syn::Fields::Unnamed(fields) => (
Style::Tuple,
fields_from_ast(cx, &fields.unnamed, attrs, container_default),
),
syn::Fields::Unit => (Style::Unit, Vec::new()),
}
}
fn fields_from_ast<'a>(
cx: &Ctxt,
fields: &'a Punctuated<syn::Field, Token![,]>,
attrs: Option<&attr::Variant>,
container_default: &attr::Default,
) -> Vec<Field<'a>> {
fields
.iter()
.enumerate()
.map(|(i, field)| Field {
member: match &field.ident {
Some(ident) => syn::Member::Named(ident.clone()),
None => syn::Member::Unnamed(i.into()),
},
attrs: attr::Field::from_ast(cx, i, field, attrs, container_default),
ty: &field.ty,
original: field,
})
.collect()
}