xml: Custom serializers

crates/xml/derive/src/attrs.rs

@@ -59,6 +59,7 @@ pub struct FieldAttrs {
     pub common: TagAttrs,
     pub flatten: Flag,
     pub default: Option<syn::ExprPath>,
+    pub serialize_with: Option<syn::ExprPath>,
     #[darling(default, rename = "ty")]
     pub xml_ty: FieldType,
 }

crates/xml/derive/src/field.rs

@@ -251,6 +251,11 @@ impl Field {
     pub fn tag_writer(&self) -> Option<proc_macro2::TokenStream> {
         let field_ident = self.field_ident();
         let field_name = self.xml_name();
+        let serializer = if let Some(serialize_with) = &self.attrs.serialize_with {
+            quote! { #serialize_with }
+        } else {
+            quote! { ::rustical_xml::XmlSerialize::serialize }
+        };
 
         match (&self.attrs.xml_ty, self.attrs.flatten.is_present()) {
             (FieldType::Attr, _) => None,
@@ -264,19 +269,19 @@ impl Field {
             }),
             (FieldType::Tag, true) => Some(quote! {
                 for item in self.#field_ident.iter() {
-                    ::rustical_xml::XmlSerialize::serialize(item, None, Some(#field_name), writer)?;
+                    #serializer(item, None, Some(#field_name), writer)?;
                 }
             }),
             (FieldType::Tag, false) => Some(quote! {
-                ::rustical_xml::XmlSerialize::serialize(&self.#field_ident, None, Some(#field_name), writer)?;
+                #serializer(&self.#field_ident, None, Some(#field_name), writer)?;
             }),
             (FieldType::Untagged, true) => Some(quote! {
                 for item in self.#field_ident.iter() {
-                    ::rustical_xml::XmlSerialize::serialize(item, None, None, writer)?;
+                    #serializer(item, None, None, writer)?;
                 }
             }),
             (FieldType::Untagged, false) => Some(quote! {
-                ::rustical_xml::XmlSerialize::serialize(&self.#field_ident, None, None, writer)?;
+                #serializer(&self.#field_ident, None, None, writer)?;
             }),
             // TODO: Think about what to do here
             (FieldType::TagName | FieldType::Namespace, _) => None,

crates/xml/tests/se_struct.rs

@@ -1,3 +1,4 @@
+use quick_xml::Writer;
 use rustical_xml::{XmlRootTag, XmlSerialize, XmlSerializeRoot};
 use xml_derive::XmlDeserialize;
 
@@ -120,3 +121,32 @@ fn test_struct_vec() {
         "<document><href>okay</href><href>wow</href></document>"
     );
 }
+
+#[test]
+fn test_struct_serialize_with() {
+    #[derive(Debug, XmlRootTag, XmlSerialize, PartialEq)]
+    #[xml(root = b"document")]
+    struct Document {
+        #[xml(serialize_with = "serialize_href")]
+        href: String,
+    }
+
+    fn serialize_href<W: ::std::io::Write>(
+        val: &String,
+        ns: Option<&[u8]>,
+        tag: Option<&[u8]>,
+        writer: &mut Writer<W>,
+    ) -> std::io::Result<()> {
+        val.to_uppercase().serialize(ns, tag, writer)
+    }
+
+    let mut buf = Vec::new();
+    let mut writer = quick_xml::Writer::new(&mut buf);
+    Document {
+        href: "okay".to_owned(),
+    }
+    .serialize_root(&mut writer)
+    .unwrap();
+    let out = String::from_utf8(buf).unwrap();
+    assert_eq!(out, "<document><href>OKAY</href></document>");
+}