initial commit

crates/router_derive/src/macros/helpers.rs

@@ -0,0 +1,33 @@
+use proc_macro2::Span;
+use quote::ToTokens;
+use syn::{parse::Parse, punctuated::Punctuated, spanned::Spanned, Attribute, Token};
+
+pub fn non_enum_error() -> syn::Error {
+    syn::Error::new(Span::call_site(), "This macro only supports enums.")
+}
+
+pub(super) fn occurrence_error<T: ToTokens>(
+    first_keyword: T,
+    second_keyword: T,
+    attr: &str,
+) -> syn::Error {
+    let mut error = syn::Error::new_spanned(
+        second_keyword,
+        format!("Found multiple occurrences of error({})", attr),
+    );
+    error.combine(syn::Error::new_spanned(first_keyword, "first one here"));
+    error
+}
+
+pub(super) fn get_metadata_inner<'a, T: Parse + Spanned>(
+    ident: &str,
+    attrs: impl IntoIterator<Item = &'a Attribute>,
+) -> syn::Result<Vec<T>> {
+    attrs
+        .into_iter()
+        .filter(|attr| attr.path.is_ident(ident))
+        .try_fold(Vec::new(), |mut vec, attr| {
+            vec.extend(attr.parse_args_with(Punctuated::<T, Token![,]>::parse_terminated)?);
+            Ok(vec)
+        })
+}