Better errors for unknown prefixes

instant-xml/src/de.rs

@@ -134,7 +134,9 @@ impl<'xml> Context<'xml> {
     pub(crate) fn element_id(&self, element: &Element<'xml>) -> Result<Id<'xml>, Error> {
         Ok(Id {
             ns: match (element.default_ns, element.prefix) {
-                (_, Some(prefix)) => self.lookup(prefix).ok_or(Error::WrongNamespace)?,
+                (_, Some(prefix)) => self
+                    .lookup(prefix)
+                    .ok_or_else(|| Error::UnknownPrefix(prefix.to_owned()))?,
                 (Some(ns), None) => ns,
                 (None, None) => self.default_ns(),
             },
@@ -145,7 +147,9 @@ impl<'xml> Context<'xml> {
     fn attribute_id(&self, attr: &Attribute<'xml>) -> Result<Id<'xml>, Error> {
         Ok(Id {
             ns: match attr.prefix {
-                Some(ns) => self.lookup(ns).ok_or(Error::WrongNamespace)?,
+                Some(ns) => self
+                    .lookup(ns)
+                    .ok_or_else(|| Error::UnknownPrefix(ns.to_owned()))?,
                 None => self.default_ns(),
             },
             name: attr.local,

instant-xml/src/lib.rs

@@ -108,16 +108,14 @@ pub enum Error {
     MissingValue(&'static Kind<'static>),
     #[error("unexpected token: {0}")]
     UnexpectedToken(String),
-    #[error("missing prefix")]
-    MissingdPrefix,
+    #[error("unknown prefix: {0}")]
+    UnknownPrefix(String),
     #[error("unexpected node: {0}")]
     UnexpectedNode(String),
     #[error("unexpected state: {0}")]
     UnexpectedState(&'static str),
     #[error("expected scalar")]
     ExpectedScalar,
-    #[error("wrong namespace")]
-    WrongNamespace,
     #[error("duplicate value")]
     DuplicateValue,
 }

instant-xml/tests/de-ns.rs

@@ -105,7 +105,7 @@ fn other_namespaces() {
         from_str(
             "<NestedOtherNamespace xmlns=\"URI\" xmlns:bar=\"BAZ\"><wrong:flag>true</wrong:flag></NestedOtherNamespace>"
         ),
-        Err::<NestedOtherNamespace, _>(Error::WrongNamespace)
+        Err::<NestedOtherNamespace, _>(Error::UnknownPrefix("wrong".to_owned()))
     );
 
     // Other namespace not-nested - wrong parser namespace
@@ -153,6 +153,6 @@ fn other_namespaces() {
         from_str(
             "<StructOtherNamespace xmlns=\"URI\" xmlns:bar=\"BAZ\"><NestedOtherNamespace><wrong:flag>true</wrong:flag></NestedOtherNamespace></StructOtherNamespace>"
         ),
-        Err::<StructOtherNamespace, _>(Error::WrongNamespace)
+        Err::<StructOtherNamespace, _>(Error::UnknownPrefix("wrong".to_owned()))
     );
 }