78 lines
1.8 KiB
Rust
78 lines
1.8 KiB
Rust
use std::collections::BTreeSet;
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use darling::{Error, FromDeriveInput, Result};
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use syn::{parse_quote, Ident};
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fn check_ident(ident: &Ident) -> Result<String> {
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let s = ident.to_string();
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if s.len() < 2 {
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Err(Error::custom("generics must be at least 2 characters").with_span(ident))
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} else {
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Ok(s)
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}
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}
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fn long_generic_names(generics: &syn::Generics) -> Result<BTreeSet<String>> {
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let mut errors = Error::accumulator();
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let valid = generics
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.type_params()
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.filter_map(|c| errors.handle(check_ident(&c.ident)))
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.collect();
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errors.finish_with(valid)
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}
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#[derive(Debug, FromDeriveInput)]
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#[darling(attributes(a))]
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struct Receiver {
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#[darling(with = long_generic_names)]
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generics: BTreeSet<String>,
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surname: String,
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}
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#[test]
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fn succeeds_on_no_generics() {
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let di = Receiver::from_derive_input(&parse_quote! {
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#[a(surname = "Smith")]
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struct Demo;
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})
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.unwrap();
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assert!(di.generics.is_empty());
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}
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#[test]
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fn succeeds_on_valid_generics() {
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let di = Receiver::from_derive_input(&parse_quote! {
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#[a(surname = "Smith")]
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struct Demo<Greeting> {
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hello: Greeting,
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world: String,
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}
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})
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.unwrap();
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assert_eq!(di.generics.len(), 1);
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assert!(di.generics.contains("Greeting"));
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assert_eq!(di.surname, "Smith");
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}
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#[test]
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fn rejects_invalid_input() {
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let err = Receiver::from_derive_input(&parse_quote! {
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struct Demo<G, S> {
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hello: G,
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world: S,
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}
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})
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.unwrap_err();
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assert_eq!(
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err.len(),
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// 2 errors from short type param names
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2 +
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// error for missing field `surname`
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1,
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"errors should have accumulated, and body checking should have occurred"
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);
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}
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