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use quote::{Tokens, ToTokens};
use syn::{Ident, Path, Type};
use codegen::DefaultExpression;
/// Properties needed to generate code for a field in all the contexts
/// where one may appear.
#[derive(Debug, Clone, PartialEq, Eq)]
pub struct Field<'a> {
/// The name presented to the user of the library. This will appear
/// in error messages and will be looked when parsing names.
pub name_in_attr: &'a str,
/// The name presented to the author of the library. This will appear
/// in the setters or temporary variables which contain the values.
pub ident: &'a Ident,
/// The type of the field in the input.
pub ty: &'a Type,
pub default_expression: Option<DefaultExpression<'a>>,
pub with_path: Path,
pub map: Option<&'a Path>,
pub skip: bool,
pub multiple: bool,
}
impl<'a> Field<'a> {
pub fn as_declaration(&'a self) -> Declaration<'a> {
Declaration(self, !self.skip)
}
pub fn as_match(&'a self) -> MatchArm<'a> {
MatchArm(self)
}
pub fn as_initializer(&'a self) -> Initializer<'a> {
Initializer(self)
}
pub fn as_presence_check(&'a self) -> CheckMissing<'a> {
CheckMissing(self)
}
}
/// An individual field during variable declaration in the generated parsing method.
pub struct Declaration<'a>(&'a Field<'a>, bool);
impl<'a> Declaration<'a> {
/// Creates a new declaration with the given field and mutability.
pub fn new(field: &'a Field<'a>, mutable: bool) -> Self {
Declaration(field, mutable)
}
}
impl<'a> ToTokens for Declaration<'a> {
fn to_tokens(&self, tokens: &mut Tokens) {
let field: &Field = self.0;
let ident = field.ident;
let ty = field.ty;
let mutable = if self.1 { quote!(mut) } else { quote!() };
tokens.append_all(if field.multiple {
// This is NOT mutable, as it will be declared mutable only temporarily.
quote!(let #mutable #ident: #ty = ::darling::export::Default::default();)
} else {
quote!(let #mutable #ident: (bool, ::darling::export::Option<#ty>) = (false, None);)
});
}
}
/// Represents an individual field in the match.
pub struct MatchArm<'a>(&'a Field<'a>);
impl<'a> ToTokens for MatchArm<'a> {
fn to_tokens(&self, tokens: &mut Tokens) {
let field: &Field = self.0;
if !field.skip {
let name_str = field.name_in_attr;
let ident = field.ident;
let with_path = &field.with_path;
// Errors include the location of the bad input, so we compute that here.
// Fields that take multiple values add the index of the error for convenience,
// while single-value fields only expose the name in the input attribute.
let location = if field.multiple {
// we use the local variable `len` here because location is accessed via
// a closure, and the borrow checker gets very unhappy if we try to immutably
// borrow `#ident` in that closure when it was declared `mut` outside.
quote!(&format!("{}[{}]", #name_str, __len))
} else {
quote!(#name_str)
};
let mut extractor = quote!(#with_path(__inner).map_err(|e| e.at(#location)));
if let Some(ref map) = field.map {
extractor = quote!(#extractor.map(#map))
}
tokens.append_all(if field.multiple {
quote!(
#name_str => {
// Store the index of the name we're assessing in case we need
// it for error reporting.
let __len = #ident.len();
match #extractor {
Ok(__val) => {
#ident.push(__val)
}
Err(__err) => {
__errors.push(__err)
}
}
}
)
} else {
quote!(
#name_str => {
if !#ident.0 {
match #extractor {
Ok(__val) => {
#ident = (true, ::darling::export::Some(__val));
}
Err(__err) => {
#ident = (true, None);
__errors.push(__err);
}
}
} else {
__errors.push(::darling::Error::duplicate_field(#name_str));
}
}
)
});
}
}
}
/// Wrapper to generate initialization code for a field.
pub struct Initializer<'a>(&'a Field<'a>);
impl<'a> ToTokens for Initializer<'a> {
fn to_tokens(&self, tokens: &mut Tokens) {
let field: &Field = self.0;
let ident = field.ident;
tokens.append_all(if field.multiple {
if let Some(ref expr) = field.default_expression {
quote!(#ident: if !#ident.is_empty() {
#ident
} else {
#expr
})
} else {
quote!(#ident: #ident)
}
} else {
if let Some(ref expr) = field.default_expression {
quote!(#ident: match #ident.1 {
::darling::export::Some(__val) => __val,
::darling::export::None => #expr,
})
} else {
quote!(#ident: #ident.1.expect("Uninitialized fields without defaults were already checked"))
}
});
}
}
/// Creates an error if a field has no value and no default.
pub struct CheckMissing<'a>(&'a Field<'a>);
impl<'a> ToTokens for CheckMissing<'a> {
fn to_tokens(&self, tokens: &mut Tokens) {
if !self.0.multiple && self.0.default_expression.is_none() {
let ident = self.0.ident;
let name_in_attr = self.0.name_in_attr;
tokens.append_all(quote! {
if !#ident.0 {
__errors.push(::darling::Error::missing_field(#name_in_attr));
}
})
}
}
}