feat: add support for nested Vec attributes in serialization

Author: jondo2010

yaserde/tests/serializer.rs

@@ -442,3 +442,28 @@ fn ser_vec_as_attribute() {
   let content = r#"<TestTag numbers="1 2 3 4" strings="hello world" bools="true false true" floats="3.14 2.71" />"#;
   serialize_and_validate!(model, content);
 }
+
+#[test]
+fn ser_vec_as_attribute_nested() {
+  #[derive(YaSerialize, PartialEq, Debug)]
+  #[yaserde(rename = "TestTag")]
+  struct VecAttributeStruct {
+    #[yaserde(attribute = true)]
+    outer: Vec<Inner>,
+  }
+
+  #[derive(YaSerialize, PartialEq, Debug)]
+  #[yaserde(rename = "TestTag")]
+  enum Inner {
+    One,
+    Two,
+  }
+
+  let model = VecAttributeStruct {
+    outer: vec![Inner::One, Inner::Two],
+  };
+
+  // Expected XML with space-separated attribute values
+  let content = r#"<TestTag outer="One Two" />"#;
+  serialize_and_validate!(model, content);
+}

yaserde_derive/src/ser/expand_struct.rs

@@ -142,10 +142,19 @@ pub fn serialize(
             Field::FieldOption { .. } | Field::FieldVec { .. } => {
               unimplemented!("Nested Option or Vec in Vec not supported for attributes")
             }
-            Field::FieldStruct { .. } => {
-              unimplemented!("Struct fields in Vec not supported for attributes")
-            }
-          }
+            Field::FieldStruct { .. } => field.ser_wrap_default_attribute(
+              Some(quote! {
+                self.#label
+                  .iter()
+                  .map(|item| ::yaserde::ser::to_string_content(item))
+                  .collect::<::std::result::Result<::std::vec::Vec<_>, _>>()?
+                  .join(" ")
+              }),
+              quote!({
+                struct_start_event.attr(#label_name, &yaserde_inner)
+              }),
+            ),
+          },
         }
       } else {
         match field.get_type() {