use darling::FromAttributes; use syn::parse_quote; #[derive(Default, darling::FromAttributes)] #[darling(attributes(builder), forward_attrs)] struct Params { default: Option, attrs: Vec, } #[test] fn forward_attrs_with_field() { let input: syn::DeriveInput = parse_quote! { #[doc = "Hello"] #[builder(default = 15)] struct Example; }; let parsed = Params::from_attributes(&input.attrs).unwrap(); assert!(parsed.default.is_some()); assert_eq!(parsed.attrs.len(), 1); }