Restore ability to deserialize attributes that represents XML namespace mappings (xmlns:xxx)

Cargo.toml

@@ -212,6 +212,11 @@ name = "serde-migrated"
 required-features = ["serialize"]
 path = "tests/serde-migrated.rs"
 
+[[test]]
+name = "serde-issues"
+required-features = ["serialize"]
+path = "tests/serde-issues.rs"
+
 [[test]]
 name = "async-tokio"
 required-features = ["async-tokio"]

Changelog.md

@@ -14,8 +14,14 @@
 
 ### Bug Fixes
 
+- [#537]: Restore ability to deserialize attributes that represents XML namespace
+  mappings (`xmlns:xxx`) that was broken since [#490]
+
 ### Misc Changes
 
+[#490]: https://github.com/tafia/quick-xml/pull/490
+[#537]: https://github.com/tafia/quick-xml/issues/537
+
 ## 0.27.1 -- 2022-12-28
 
 ### Bug Fixes

src/de/key.rs

@@ -35,9 +35,11 @@ fn decode_name<'n>(name: QName<'n>, decoder: Decoder) -> Result<Cow<'n, str>, De
 /// Converts a name to an identifier string using the following rules:
 ///
 /// - if it is an [`attribute`] name, put `@` in front of the identifier
+/// - if it is a namespace binding (`xmlns` or `xmlns:xxx`) put the decoded name
+///   to the identifier
 /// - put the decoded [`local_name()`] of a name to the identifier
 ///
-/// The final identifier looks like `[@]local_name`
+/// The final identifier looks like `[@]local_name`, or `@xmlns`, or `@xmlns:binding`
 /// (where `[]` means optional element).
 ///
 /// The deserializer also supports deserializing names as other primitive types:
@@ -72,10 +74,16 @@ pub struct QNameDeserializer<'d> {
 impl<'d> QNameDeserializer<'d> {
     /// Creates deserializer from name of an attribute
     pub fn from_attr(name: QName<'d>, decoder: Decoder) -> Result<Self, DeError> {
-        let local = decode_name(name, decoder)?;
+        // https://github.com/tafia/quick-xml/issues/537
+        // Namespace bindings (xmlns:xxx) map to `@xmlns:xxx` instead of `@xxx`
+        let field = if name.as_namespace_binding().is_some() {
+            decoder.decode(name.into_inner())?
+        } else {
+            decode_name(name, decoder)?
+        };
 
         Ok(Self {
-            name: Cow::Owned(format!("@{local}")),
+            name: Cow::Owned(format!("@{field}")),
         })
     }
 

tests/issues.rs

@@ -1,6 +1,6 @@
-//! Regression tests found in various issues
+//! Regression tests found in various issues.
 //!
-//! Name each test as `issue<GH number>`
+//! Name each module / test as `issue<GH number>` and keep sorted by issue number
 
 use quick_xml::events::{BytesStart, Event};
 use quick_xml::reader::Reader;

tests/serde-issues.rs

@@ -0,0 +1,60 @@
+//! Regression tests found in various issues with serde integration.
+//!
+//! Name each module / test as `issue<GH number>` and keep sorted by issue number
+
+use quick_xml::de::from_str;
+use quick_xml::se::to_string;
+use serde::{Deserialize, Serialize};
+
+/// Regression test for https://github.com/tafia/quick-xml/issues/537.
+///
+/// This test checks that special `xmlns:xxx` attributes uses full name of
+/// an attribute (xmlns:xxx) as a field name instead of just local name of
+/// an attribute (xxx)
+mod issue537 {
+    use super::*;
+    use pretty_assertions::assert_eq;
+
+    #[derive(Debug, PartialEq, Deserialize, Serialize)]
+    struct Bindings<'a> {
+        /// Default namespace binding
+        #[serde(rename = "@xmlns")]
+        xmlns: &'a str,
+
+        /// Named namespace binding
+        #[serde(rename = "@xmlns:named")]
+        xmlns_named: &'a str,
+
+        /// Usual attribute
+        #[serde(rename = "@attribute")]
+        attribute: &'a str,
+    }
+
+    #[test]
+    fn de() {
+        assert_eq!(
+            from_str::<Bindings>(
+                r#"<Bindings xmlns="default" xmlns:named="named" attribute="attribute"/>"#
+            )
+            .unwrap(),
+            Bindings {
+                xmlns: "default",
+                xmlns_named: "named",
+                attribute: "attribute",
+            }
+        );
+    }
+
+    #[test]
+    fn se() {
+        assert_eq!(
+            to_string(&Bindings {
+                xmlns: "default",
+                xmlns_named: "named",
+                attribute: "attribute",
+            })
+            .unwrap(),
+            r#"<Bindings xmlns="default" xmlns:named="named" attribute="attribute"/>"#
+        );
+    }
+}