From 98ed1a3fc50422e7f239ed82412b305c6712169f Mon Sep 17 00:00:00 2001
From: Lennart <18233294+lennart-k@users.noreply.github.com>
Date: Mon, 23 Dec 2024 13:02:59 +0100
Subject: [PATCH] xml: Implement XmlDocument for tagged enums and fix small bug

---
 crates/xml/derive/src/de/de_enum.rs | 33 +++++++++++++++++++++++++++++
 crates/xml/derive/src/lib.rs        | 12 +++++++++++
 crates/xml/src/de.rs                |  3 ++-
 crates/xml/src/lib.rs               |  1 +
 crates/xml/tests/de_enum.rs         | 17 +++++++++++++++
 5 files changed, 65 insertions(+), 1 deletion(-)

diff --git a/crates/xml/derive/src/de/de_enum.rs b/crates/xml/derive/src/de/de_enum.rs
index 8e22b64..fc548e9 100644
--- a/crates/xml/derive/src/de/de_enum.rs
+++ b/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)
+                }
+            }
+        }
+    }
 }
diff --git a/crates/xml/derive/src/lib.rs b/crates/xml/derive/src/lib.rs
index 862cabf..6674c70 100644
--- a/crates/xml/derive/src/lib.rs
+++ b/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()
+}
diff --git a/crates/xml/src/de.rs b/crates/xml/src/de.rs
index 546ee76..513d179 100644
--- a/crates/xml/src/de.rs
+++ b/crates/xml/src/de.rs
@@ -2,6 +2,7 @@ use quick_xml::name::Namespace;
 use quick_xml::name::ResolveResult;
 use std::io::BufRead;
 pub use xml_derive::XmlDeserialize;
+pub use xml_derive::XmlDocument;
 pub use xml_derive::XmlRootTag;
 
 use quick_xml::events::{BytesStart, Event};
@@ -74,7 +75,7 @@ impl<T: XmlRootTag + XmlDeserialize> XmlDocument for T {
     {
         let mut buf = Vec::new();
         let event = reader.read_event_into(&mut buf)?;
-        let empty = event.is_empty();
+        let empty = matches!(event, Event::Empty(_));
         match event {
             Event::Start(start) | Event::Empty(start) => {
                 let (ns, name) = reader.resolve_element(start.name());
diff --git a/crates/xml/src/lib.rs b/crates/xml/src/lib.rs
index 2b8896d..62997df 100644
--- a/crates/xml/src/lib.rs
+++ b/crates/xml/src/lib.rs
@@ -7,6 +7,7 @@ mod value;
 
 pub use de::XmlDeError;
 pub use de::XmlDeserialize;
+pub use de::XmlDocument;
 pub use de::XmlRootTag;
 pub use se::XmlSerialize;
 pub use value::Value;
diff --git a/crates/xml/tests/de_enum.rs b/crates/xml/tests/de_enum.rs
index bcc93b4..67dabba 100644
--- a/crates/xml/tests/de_enum.rs
+++ b/crates/xml/tests/de_enum.rs
@@ -96,3 +96,20 @@ fn test_tagged_enum_complex() {
     .unwrap();
     dbg!(asd);
 }
+
+#[test]
+fn test_enum_document() {
+    #[derive(Debug, XmlDeserialize, XmlDocument, PartialEq)]
+    enum Document {
+        Hello,
+        Goodbye,
+    }
+    assert_eq!(
+        Document::parse_str(r"<hello></hello>").unwrap(),
+        Document::Hello
+    );
+    assert_eq!(
+        Document::parse_str(r"<goodbye/>").unwrap(),
+        Document::Goodbye
+    );
+}