rustical_xml: Add new trait EnumVariants

crates/xml/derive/src/lib.rs

@@ -61,3 +61,15 @@ pub fn derive_xml_document(input: proc_macro::TokenStream) -> proc_macro::TokenS
     }
     .into()
 }
+
+#[proc_macro_derive(EnumVariants, attributes(xml))]
+pub fn derive_enum_variants(input: proc_macro::TokenStream) -> proc_macro::TokenStream {
+    let input = parse_macro_input!(input as DeriveInput);
+
+    match &input.data {
+        syn::Data::Struct(_) => panic!("Struct not supported, use XmlRootTag instead"),
+        syn::Data::Enum(e) => Enum::parse(&input, e).impl_enum_variants(),
+        syn::Data::Union(_) => panic!("Union not supported as root"),
+    }
+    .into()
+}

crates/xml/derive/src/xml_enum.rs

@@ -193,4 +193,27 @@ impl Enum {
             }
         }
     }
+
+    pub fn impl_enum_variants(&self) -> proc_macro2::TokenStream {
+        let (impl_generics, type_generics, where_clause) = self.generics.split_for_impl();
+        let ident = &self.ident;
+
+        let tagged_variants = self.variants.iter().map(|variant| {
+            let ns = match &variant.attrs.common.ns {
+                Some(ns) => quote! { Some(#ns) },
+                None => quote! { None },
+            };
+            let b_xml_name = variant.xml_name().value();
+            let xml_name = String::from_utf8_lossy(&b_xml_name);
+            quote! {(#ns, #xml_name)}
+        });
+
+        quote! {
+            impl #impl_generics ::rustical_xml::EnumVariants for #ident #type_generics #where_clause {
+                const TAGGED_VARIANTS: &'static [(Option<::quick_xml::name::Namespace<'static>>, &'static str)] = &[
+                    #(#tagged_variants),*
+                ];
+            }
+        }
+    }
 }

crates/xml/src/lib.rs

@@ -14,6 +14,7 @@ pub use se::XmlSerialize;
 pub use se::XmlSerializeRoot;
 pub use unparsed::Unparsed;
 pub use value::{ParseValueError, ValueDeserialize, ValueSerialize};
+pub use xml_derive::EnumVariants;
 pub use xml_derive::XmlRootTag;
 
 pub trait XmlRootTag {
@@ -21,3 +22,7 @@ pub trait XmlRootTag {
     fn root_ns() -> Option<Namespace<'static>>;
     fn root_ns_prefixes() -> HashMap<Namespace<'static>, &'static [u8]>;
 }
+
+pub trait EnumVariants {
+    const TAGGED_VARIANTS: &'static [(Option<Namespace<'static>>, &'static str)];
+}

crates/xml/tests/enum_variants.rs

@@ -0,0 +1,36 @@
+use quick_xml::name::Namespace;
+use rustical_xml::EnumVariants;
+
+pub const NS_DAV: Namespace = Namespace(b"DAV:");
+pub const NS_DAVPUSH: Namespace = Namespace(b"https://bitfire.at/webdav-push");
+pub const NS_CALDAV: Namespace = Namespace(b"urn:ietf:params:xml:ns:caldav");
+pub const NS_CARDDAV: Namespace = Namespace(b"urn:ietf:params:xml:ns:carddav");
+pub const NS_ICAL: Namespace = Namespace(b"http://apple.com/ns/ical/");
+pub const NS_CALENDARSERVER: Namespace = Namespace(b"http://calendarserver.org/ns/");
+pub const NS_NEXTCLOUD: Namespace = Namespace(b"http://nextcloud.com/ns");
+
+#[derive(EnumVariants)]
+pub enum CalendarProp {
+    // WebDAV (RFC 2518)
+    #[xml(ns = "NS_DAV")]
+    Displayname(Option<String>),
+    #[xml(ns = "NS_DAV")]
+    Getcontenttype(&'static str),
+
+    #[xml(ns = "NS_DAV", rename = b"principal-URL")]
+    PrincipalUrl,
+    Topic,
+}
+
+#[test]
+fn test_enum_variants() {
+    assert_eq!(
+        CalendarProp::TAGGED_VARIANTS,
+        &[
+            (Some(NS_DAV), "displayname"),
+            (Some(NS_DAV), "getcontenttype"),
+            (Some(NS_DAV), "principal-URL"),
+            (None, "topic"),
+        ]
+    );
+}