implement tafia#629

src/serde_helpers.rs

@@ -118,6 +118,60 @@ macro_rules! deserialize_variant {
 /// );
 /// ```
 ///
+/// You don't have to provide all the enumeration variants and can use `_` to put every undefined tag into an enumeration variant like so:
+/// # Example
+///
+/// ```
+/// # use pretty_assertions::assert_eq;
+/// use quick_xml::de::from_str;
+/// use quick_xml::impl_deserialize_for_internally_tagged_enum;
+/// use serde::Deserialize;
+///
+/// #[derive(Deserialize, Debug, PartialEq)]
+/// struct Root {
+///     one: InternallyTaggedEnum,
+///     two: InternallyTaggedEnum,
+///     three: InternallyTaggedEnum,
+/// }
+///
+/// #[derive(Debug, PartialEq)]
+/// enum InternallyTaggedEnum {
+///     NewType(Newtype),
+///     Other,
+/// }
+///
+/// #[derive(Deserialize, Debug, PartialEq)]
+/// struct Newtype {
+///     #[serde(rename = "@attribute")]
+///     attribute: u64,
+/// }
+///
+/// // The macro needs the type of the enum, the tag name,
+/// // and information about all the variants
+/// impl_deserialize_for_internally_tagged_enum!{
+///     InternallyTaggedEnum, "@tag",
+///     ("NewType"    => NewType(Newtype)),
+///     (_  => Other),
+/// }
+///
+/// assert_eq!(
+///     from_str::<Root>(r#"
+///         <root>
+///             <one tag="NewType" attribute="42" />
+///             <two tag="Something" ignoredAttribute="something" />
+///             <three tag="SomethingElse">
+///                 <ignoredToo />
+///             </three>
+///         </root>
+///     "#).unwrap(),
+///     Root {
+///         one: InternallyTaggedEnum::NewType(Newtype { attribute: 42 }),
+///         two: InternallyTaggedEnum::Other,
+///         three: InternallyTaggedEnum::Other,
+///     },
+/// );
+/// ```
+///
 /// [internally tagged]: https://serde.rs/enum-representations.html#internally-tagged
 /// [serde#1183]: https://github.com/serde-rs/serde/issues/1183
 #[macro_export(local_inner_macros)]
@@ -127,7 +181,9 @@ macro_rules! impl_deserialize_for_internally_tagged_enum {
         $tag:literal,
         $(
             ($variant_tag:literal => $($variant:tt)+ )
-        ),* $(,)?
+        ),*
+        $(, (_ => $($default_variant:tt)+ ))?
+        $(,)*
     ) => {
         impl<'de> serde::de::Deserialize<'de> for $enum {
             fn deserialize<D>(deserializer: D) -> Result<Self, D::Error>
@@ -182,6 +238,8 @@ macro_rules! impl_deserialize_for_internally_tagged_enum {
                             $(
                                 $variant_tag => Ok(deserialize_variant!( de, $enum, $($variant)+ )),
                             )*
+                            $( _ => Ok(deserialize_variant!( de, $enum, $($default_variant)+ )), )?
+                            #[allow(unreachable)]
                             _ => Err(A::Error::unknown_field(&tag, &[$($variant_tag),+])),
                         }
                     }