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use std::collections::BTreeSet;
use darling::{util, Error, FromDeriveInput, Result};
use syn::{parse_quote, Attribute};
fn unique_idents(attrs: Vec<Attribute>) -> Result<BTreeSet<String>> {
let mut errors = Error::accumulator();
let idents = attrs
.into_iter()
.filter_map(|attr| {
let path = attr.path();
errors.handle(
path.get_ident()
.map(std::string::ToString::to_string)
.ok_or_else(|| {
Error::custom(format!("`{}` is not an ident", util::path_to_string(path)))
.with_span(path)
}),
)
})
.collect();
errors.finish_with(idents)
}
#[derive(FromDeriveInput)]
#[darling(attributes(a), forward_attrs)]
struct Receiver {
#[darling(with = unique_idents)]
attrs: BTreeSet<String>,
other: Option<bool>,
}
#[test]
fn succeeds_on_no_attrs() {
let di = Receiver::from_derive_input(&parse_quote! {
struct Demo;
})
.unwrap();
assert!(di.attrs.is_empty());
}
#[test]
fn succeeds_on_valid_input() {
let di = Receiver::from_derive_input(&parse_quote! {
#[allow(dead_code)]
/// testing
#[another]
struct Demo;
})
.unwrap();
assert_eq!(di.attrs.len(), 3);
assert!(di.attrs.contains("allow"));
assert!(di.attrs.contains("another"));
assert!(di.attrs.contains("doc"));
assert_eq!(di.other, None);
}
#[test]
fn errors_combined_with_others() {
let e = Receiver::from_derive_input(&parse_quote! {
#[path::to::attr(dead_code)]
#[a(other = 5)]
struct Demo;
})
.map(|_| "Should have failed")
.unwrap_err();
let error = e.to_string();
assert_eq!(e.len(), 2);
// Look for the error on the field `other`
assert!(error.contains("at other"));
// Look for the invalid path from attrs conversion
assert!(error.contains("`path::to::attr`"));
}