parsers: add streamable parsing

This adds shims which provide FromXml and IntoXml implementations to
*all* macro-generated types in `xmpp_parsers`. Mind that this does not
cover all types in `xmpp_parsers`, but a good share of them.

This is another first step toward real, fully streamed parsing.

parsers/src/util/error.rs

@@ -131,3 +131,18 @@ impl From<chrono::ParseError> for Error {
         Error::ChronoParseError(err)
     }
 }
+
+impl From<Error> for xso::error::Error {
+    fn from(other: Error) -> Self {
+        match other {
+            Error::ParseError(e) => Self::Other(e.to_string().into()),
+            Error::TypeMismatch { .. } => Self::TypeMismatch,
+            Error::Base64Error(e) => Self::TextParseError(Box::new(e)),
+            Error::ParseIntError(e) => Self::TextParseError(Box::new(e)),
+            Error::ParseStringError(e) => Self::TextParseError(Box::new(e)),
+            Error::ParseAddrError(e) => Self::TextParseError(Box::new(e)),
+            Error::JidParseError(e) => Self::TextParseError(Box::new(e)),
+            Error::ChronoParseError(e) => Self::TextParseError(Box::new(e)),
+        }
+    }
+}

parsers/src/util/macros.rs

@@ -676,6 +676,23 @@ macro_rules! generate_element {
             )*
         }
 
+        impl ::xso::FromXml for $elem {
+            type Builder = ::xso::minidom_compat::FromEventsViaElement<$elem>;
+
+            fn from_events(
+                qname: ::xso::exports::rxml::QName,
+                attrs: ::xso::exports::rxml::AttrMap,
+            ) -> Result<Self::Builder, ::xso::error::FromEventsError> {
+                if qname.0 != crate::ns::$ns || qname.1 != $name {
+                    return Err(::xso::error::FromEventsError::Mismatch {
+                        name: qname,
+                        attrs,
+                    })
+                }
+                Self::Builder::new(qname, attrs)
+            }
+        }
+
         impl ::std::convert::TryFrom<crate::Element> for $elem {
             type Error = crate::util::error::Error;
 
@@ -748,6 +765,14 @@ macro_rules! generate_element {
                 builder.build()
             }
         }
+
+        impl ::xso::IntoXml for $elem {
+            type EventIter = ::xso::minidom_compat::IntoEventsViaElement;
+
+            fn into_event_iter(self) -> Result<Self::EventIter, ::xso::error::Error> {
+                Self::EventIter::new(self)
+            }
+        }
     );
 }