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use proc_macro2::Span;
use syn::{Attribute, Meta, Path, Token, punctuated::Punctuated, spanned::Spanned};
use crate::{
common::{
ident_bool::{meta_2_bool_allow_path, meta_name_value_2_bool},
int::meta_2_isize,
path::meta_2_path,
},
panic,
supported_traits::Trait,
};
/// The parsed settings of a field-level `Ord` attribute.
pub(crate) struct FieldAttribute {
pub(crate) ignore: bool,
pub(crate) method: Option<Path>,
pub(crate) rank: isize,
pub(crate) rank_span: Option<Span>,
}
/// Parses field-level `Ord` metas; the `enable_*` switches describe which parameters are allowed for the current shape of data.
pub(crate) struct FieldAttributeBuilder {
pub(crate) enable_ignore: bool,
pub(crate) enable_method: bool,
pub(crate) enable_rank: bool,
pub(crate) rank: isize,
}
impl FieldAttributeBuilder {
/// Parses one field-level `Ord` meta into a `FieldAttribute`, rejecting parameters that are not enabled here.
pub(crate) fn build_from_ord_meta(&self, meta: &Meta) -> syn::Result<FieldAttribute> {
debug_assert!(meta.path().is_ident("Ord") || meta.path().is_ident("PartialOrd"));
let mut ignore = false;
let mut method = None;
let mut rank = self.rank;
let mut rank_span = None;
let correct_usage_for_partial_eq_attribute = {
let mut usage = vec![];
if self.enable_ignore {
usage.push(stringify!(#[educe(Ord = false)]));
usage.push(stringify!(#[educe(Ord(ignore))]));
}
if self.enable_method {
usage.push(stringify!(#[educe(Ord(method(path_to_method)))]));
}
if self.enable_rank {
usage.push(stringify!(#[educe(Ord(rank = integer))]));
}
usage
};
match meta {
Meta::Path(_) => {
return Err(panic::attribute_incorrect_format(
meta.path().get_ident().unwrap(),
&correct_usage_for_partial_eq_attribute,
));
},
Meta::NameValue(name_value) => {
if self.enable_ignore {
ignore = !meta_name_value_2_bool(name_value)?;
} else {
return Err(panic::attribute_incorrect_format(
meta.path().get_ident().unwrap(),
&correct_usage_for_partial_eq_attribute,
));
}
},
Meta::List(list) => {
let result =
list.parse_args_with(Punctuated::<Meta, Token![,]>::parse_terminated)?;
let mut ignore_is_set = false;
let mut method_is_set = false;
let mut rank_is_set = false;
let mut handler = |meta: Meta| -> syn::Result<bool> {
if let Some(ident) = meta.path().get_ident() {
match ident.to_string().as_str() {
"ignore" => {
if !self.enable_ignore {
return Ok(false);
}
let v = meta_2_bool_allow_path(&meta)?;
if ignore_is_set {
return Err(panic::parameter_reset(ident));
}
ignore_is_set = true;
ignore = v;
return Ok(true);
},
"method" => {
if !self.enable_method {
return Ok(false);
}
let v = meta_2_path(&meta)?;
if method_is_set {
return Err(panic::parameter_reset(ident));
}
method_is_set = true;
method = Some(v);
return Ok(true);
},
"rank" => {
if !self.enable_rank {
return Ok(false);
}
let v = meta_2_isize(&meta)?;
if rank_is_set {
return Err(panic::parameter_reset(ident));
}
rank_is_set = true;
rank = v;
rank_span = Some(meta.span());
return Ok(true);
},
_ => (),
}
}
Ok(false)
};
for p in result {
if !handler(p)? {
return Err(panic::attribute_incorrect_format(
meta.path().get_ident().unwrap(),
&correct_usage_for_partial_eq_attribute,
));
}
}
},
}
Ok(FieldAttribute {
ignore,
method,
rank,
rank_span,
})
}
/// Scans the `#[educe(...)]` attributes of a field and parses its `Ord` meta if present.
pub(crate) fn build_from_attributes(
&self,
attributes: &[Attribute],
traits: &[Trait],
) -> syn::Result<FieldAttribute> {
let mut output = None;
// When `PartialOrd` is derived together and a field has no `Ord` attribute of its own, the `ignore` and `rank` settings of the field's `PartialOrd` attribute are used instead, so that `cmp` stays consistent with `partial_cmp`.
#[cfg(feature = "PartialOrd")]
let mut fallback = None;
for attribute in attributes.iter() {
let path = attribute.path();
if path.is_ident("educe")
&& let Meta::List(list) = &attribute.meta
{
let result =
list.parse_args_with(Punctuated::<Meta, Token![,]>::parse_terminated)?;
for meta in result {
let path = meta.path();
let t = match Trait::from_path(path) {
Some(t) => t,
None => return Err(panic::unsupported_trait(meta.path())),
};
if !traits.contains(&t) {
return Err(panic::trait_not_used(path.get_ident().unwrap()));
}
if t == Trait::Ord {
if output.is_some() {
return Err(panic::reuse_a_trait(path.get_ident().unwrap()));
}
output = Some(self.build_from_ord_meta(&meta)?);
}
// A malformed `PartialOrd` attribute is silently skipped here; the `PartialOrd` handler itself reports it with the proper usage message.
#[cfg(feature = "PartialOrd")]
if t == Trait::PartialOrd
&& fallback.is_none()
&& let Ok(mut field_attribute) = self.build_from_ord_meta(&meta)
{
// A `PartialOrd` comparison method returns `Option<Ordering>` and cannot be used by the generated `cmp`, so only `ignore` and `rank` are taken over.
field_attribute.method = None;
fallback = Some(field_attribute);
}
}
}
}
#[cfg(feature = "PartialOrd")]
let output = output.or(fallback);
Ok(output.unwrap_or(FieldAttribute {
ignore: false,
method: None,
rank: self.rank,
rank_span: None,
}))
}
}