implement Clone and other improvements for Error

src/error.rs

@@ -2,13 +2,17 @@ use std::{
     collections::{HashMap, VecDeque},
     num::ParseIntError,
     str::Utf8Error,
+    sync::Arc,
 };
 
 use thiserror::Error;
 
-use crate::element::{Content, Name, NamespaceDeclaration};
+use crate::{
+    element::{Content, Name, NamespaceDeclaration},
+    Element,
+};
 
-#[derive(Error, Debug)]
+#[derive(Error, Debug, Clone)]
 pub enum DeserializeError {
     #[error("could not parse string {0:?} to requested value")]
     FromStr(String),
@@ -28,19 +32,23 @@ pub enum DeserializeError {
     MissingChild,
     #[error("element missing expected text value")]
     MissingValue,
+    // not used by crate (yet), but may be used by consumers implementing FromElement
+    #[error("unexpected element: {0:?}")]
+    UnexpectedElement(Element),
 }
 
-#[derive(Error, Debug)]
+#[derive(Error, Debug, Clone)]
 pub enum Error {
-    #[error(transparent)]
-    ReadError(#[from] std::io::Error),
-    #[error(transparent)]
+    #[error("io: {0}")]
+    // TODO: is this okay?
+    ReadError(Arc<std::io::Error>),
+    #[error("utf8 conversion: {0}")]
     Utf8Error(#[from] Utf8Error),
-    #[error("nom parse error: {0}")]
+    #[error("nom parsing: {0}")]
     ParseError(String),
     #[error("unknown xml entity reference `&{0};`")]
     EntityProcessError(String),
-    #[error(transparent)]
+    #[error("invalid character reference: {0}")]
     InvalidCharRef(CharRefError),
     #[error("duplicate namespace declaration: {0:?}")]
     DuplicateNameSpaceDeclaration(NamespaceDeclaration),
@@ -54,16 +62,21 @@ pub enum Error {
     ExtraData(String),
     #[error("namespace `{0}` has not previously been declared")]
     UndeclaredNamespace(String),
-    #[error(transparent)]
+    #[error("deserialization error: {0}")]
     Deserialize(#[from] DeserializeError),
-    /// root element end tag already processed
     #[error("root element has already been fully processed")]
     RootElementEnded,
 }
 
-#[derive(Error, Debug)]
+impl From<std::io::Error> for Error {
+    fn from(e: std::io::Error) -> Self {
+        Self::ReadError(Arc::new(e))
+    }
+}
+
+#[derive(Error, Debug, Clone)]
 pub enum CharRefError {
-    #[error(transparent)]
+    #[error("int parsing: {0}")]
     ParseInt(#[from] ParseIntError),
     #[error("u32 `{0}` does not represent a valid char")]
     IntegerNotAChar(u32),