Pass through all other attributes to discriminant enum.

Issue Peternator7#33

strum_macros/src/enum_discriminants.rs

@@ -1,7 +1,9 @@
 use proc_macro2::{Span, TokenStream};
 use syn;
 
-use helpers::{extract_list_metas, extract_meta, get_meta_ident, get_meta_list, unique_meta_list};
+use helpers::{
+    extract_list_metas, extract_meta, filter_metas, get_meta_ident, get_meta_list, unique_meta_list,
+};
 
 pub fn enum_discriminants_inner(ast: &syn::DeriveInput) -> TokenStream {
     let name = &ast.ident;
@@ -37,6 +39,14 @@ pub fn enum_discriminants_inner(ast: &syn::DeriveInput) -> TokenStream {
         .and_then(|metas| metas.filter_map(get_meta_ident).next())
         .unwrap_or(&default_name);
 
+    // Pass through all other attributes
+    let pass_though_attributes =
+        filter_metas(discriminant_attrs.iter().map(|&m| m), |meta| match meta {
+            syn::Meta::List(ref metalist) => metalist.ident != "derive" && metalist.ident != "name",
+            _ => true,
+        }).map(|meta| quote! { #[ #meta ] })
+        .collect::<Vec<_>>();
+
     // Add the variants without fields, but exclude the `strum` meta item
     let mut discriminants = Vec::new();
     for variant in variants {
@@ -56,6 +66,7 @@ pub fn enum_discriminants_inner(ast: &syn::DeriveInput) -> TokenStream {
     quote!{
         /// Auto-generated discriminant enum variants
         #derives
+        #(#pass_though_attributes)*
         #vis enum #discriminants_name {
             #(#discriminants),*
         }

strum_macros/src/helpers.rs

@@ -10,6 +10,34 @@ pub fn extract_meta(attrs: &[Attribute]) -> Vec<Meta> {
         .collect()
 }
 
+pub fn filter_metas<'meta, MetaIt, F>(metas: MetaIt, filter: F) -> impl Iterator<Item = &'meta Meta>
+where
+    MetaIt: Iterator<Item = &'meta Meta>,
+    F: Fn(&Meta) -> bool,
+{
+    metas.filter_map(move |meta| if filter(meta) { Some(meta) } else { None })
+}
+
+pub fn filter_meta_lists<'meta, MetaIt, F>(
+    metas: MetaIt,
+    filter: F,
+) -> impl Iterator<Item = &'meta MetaList>
+where
+    MetaIt: Iterator<Item = &'meta Meta>,
+    F: Fn(&MetaList) -> bool,
+{
+    metas.filter_map(move |meta| match meta {
+        Meta::List(ref metalist) => {
+            if filter(metalist) {
+                Some(metalist)
+            } else {
+                None
+            }
+        }
+        _ => None,
+    })
+}
+
 /// Returns the `MetaList`s with the given attr name.
 ///
 /// For example, `get_meta_list(type_meta.iter(), "strum_discriminant")` for the following snippet
@@ -29,18 +57,7 @@ pub fn get_meta_list<'meta, MetaIt>(
 where
     MetaIt: Iterator<Item = &'meta Meta>,
 {
-    metas
-        // Get all the attributes with our tag on them.
-        .filter_map(move |meta| match meta {
-            Meta::List(ref metalist) => {
-                if metalist.ident == attr {
-                    Some(metalist)
-                } else {
-                    None
-                }
-            }
-            _ => None,
-        })
+    filter_meta_lists(metas, move |metalist| metalist.ident == attr)
 }
 
 pub fn unique_meta_list<'meta, MetaIt>(metas: MetaIt, attr: &'meta str) -> Option<&'meta MetaList>

strum_tests/tests/enum_discriminants.rs

@@ -118,3 +118,30 @@ fn split_attributes_test() {
     assert_eq!(expected, discriminants);
     assert_eq!("Variant0", format!("{}", SplitAttributesBoo::Variant0));
 }
+
+#[allow(dead_code)]
+#[derive(Debug, Eq, PartialEq, EnumDiscriminants)]
+#[strum_discriminants(
+    name(PassThroughBoo),
+    derive(Display, EnumIter, EnumString),
+    strum(serialize_all = "snake_case"),
+)]
+enum PassThrough {
+    DarkBlack(bool),
+    BrightWhite(i32),
+}
+
+#[test]
+fn arbitrary_attributes_pass_through() {
+    use std::str::FromStr;
+
+    let discriminants = PassThroughBoo::iter().collect::<Vec<_>>();
+    let expected = vec![PassThroughBoo::DarkBlack, PassThroughBoo::BrightWhite];
+
+    assert_eq!(expected, discriminants);
+    assert_eq!("dark_black", PassThroughBoo::DarkBlack.to_string());
+    assert_eq!(
+        PassThroughBoo::DarkBlack,
+        PassThroughBoo::from_str("dark_black").unwrap()
+    );
+}