Properly add the xml version header and imports to the output xml

lib/src/saves/def/mod.rs

@@ -25,6 +25,12 @@ pub type AreaId = u16;
 /// The root of a celeste save file
 #[derive(Serialize, Deserialize, Debug, Clone)]
 pub struct SaveData {
+    #[doc(hidden)]
+    #[serde(rename(serialize = "@xmlns:xsi", deserialize = "@xmlns:xsi"))]
+    xsi_url: String,
+    #[doc(hidden)]
+    #[serde(rename(serialize = "@xmlns:xsd", deserialize = "@xmlns:xsd"))]
+    xsd_url: String,
     /// The last celeste version that the save file was opened with
     #[serde(rename = "Version")]
     pub version: String,

lib/src/saves/ops/mod.rs

@@ -24,6 +24,8 @@ pub mod session;
 pub mod util;
 pub mod vanilla;
 
+const XML_VERSION_HEADER: &str = r#"<?xml version="1.0" encoding="utf-8"?>"#;
+
 fn area_sid_matches(area: &AreaStats, sid: &str) -> bool {
     area.def.sid.as_ref().is_some_and(|a_sid| a_sid == sid)
 }
@@ -39,10 +41,13 @@ impl SaveData {
     }
 
     pub fn to_string(&self) -> Result<String, DeError> {
-        quick_xml::se::to_string(&self)
+        let mut xml = XML_VERSION_HEADER.to_owned();
+        xml.push_str(&quick_xml::se::to_string(&self)?);
+        Ok(xml)
     }
 
-    pub fn to_writer(&self, writer: impl Write) -> Result<(), DeError> {
+    pub fn to_writer(&self, mut writer: impl Write) -> Result<(), DeError> {
+        writer.write_str(XML_VERSION_HEADER)?;
         quick_xml::se::to_writer(writer, &self)
     }