xml: Implement XmlDocument for tagged enums and fix small bug

crates/xml/derive/src/de/de_enum.rs

@@ -1,3 +1,5 @@
+use core::panic;
+
 use super::attrs::EnumAttrs;
 use crate::de::attrs::VariantAttrs;
 use darling::{FromDeriveInput, FromVariant};
@@ -219,4 +221,35 @@ impl Enum {
             }
         }
     }
+
+    pub fn impl_xml_document(&self) -> proc_macro2::TokenStream {
+        if self.attrs.untagged.is_present() {
+            panic!("XmlDocument only supported for untagged enums");
+        }
+        let (impl_generics, type_generics, where_clause) = self.generics.split_for_impl();
+        let ident = &self.ident;
+
+        quote! {
+            impl #impl_generics ::rustical_xml::XmlDocument for #ident #type_generics #where_clause {
+                fn parse<R: ::std::io::BufRead>(mut reader: ::quick_xml::NsReader<R>) -> Result<Self, ::rustical_xml::XmlDeError>
+                where
+                    Self: ::rustical_xml::XmlDeserialize
+                {
+                    use ::quick_xml::events::Event;
+
+                    let mut buf = Vec::new();
+                    let event = reader.read_event_into(&mut buf)?;
+                    let empty = matches!(event, Event::Empty(_));
+
+                    match event {
+                        Event::Start(start) | Event::Empty(start) => {
+                            return Self::deserialize(&mut reader, &start, empty);
+                        }
+                        _ => {}
+                    };
+                    Err(::rustical_xml::XmlDeError::UnknownError)
+                }
+            }
+        }
+    }
 }

crates/xml/derive/src/lib.rs

@@ -39,3 +39,15 @@ pub fn derive_xml_root_tag(input: proc_macro::TokenStream) -> proc_macro::TokenS
     }
     .into()
 }
+
+#[proc_macro_derive(XmlDocument, attributes(xml))]
+pub fn derive_xml_document(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_xml_document(),
+        syn::Data::Union(_) => panic!("Union not supported as root"),
+    }
+    .into()
+}