From 11a5c49470d1e3d8875a7ccefc0cbd34855eafe7 Mon Sep 17 00:00:00 2001
From: Emmanuel Gil Peyrot <linkmauve@linkmauve.fr>
Date: Sat, 7 Sep 2019 16:02:40 +0200
Subject: [PATCH] Implement std::error::Error for Error.
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This was removed in 0.11.1 with the removal of failure, but is used by
people so let’s reintroduce it.

The cause of an XmlError is pending on this PR from quick-xml:
https://github.com/tafia/quick-xml/pull/170

Fixes #15.
Fixes #18.
---
 src/error.rs | 18 ++++++++++++++++++
 1 file changed, 18 insertions(+)

diff --git a/src/error.rs b/src/error.rs
index fc96a08..579cee4 100644
--- a/src/error.rs
+++ b/src/error.rs
@@ -1,6 +1,7 @@
 //! Provides an error type for this crate.
 
 use std::convert::From;
+use std::error::Error as StdError;
 
 /// Our main error type.
 #[derive(Debug)]
@@ -28,6 +29,23 @@ pub enum Error {
     CommentsDisabled,
 }
 
+impl StdError for Error {
+    fn cause(&self) -> Option<&dyn StdError> {
+        match self {
+            // TODO: return Some(e) for this case after the merge of
+            // https://github.com/tafia/quick-xml/pull/170
+            Error::XmlError(_e) => None,
+            Error::Utf8Error(e) => Some(e),
+            Error::IoError(e) => Some(e),
+            Error::EndOfDocument => None,
+            Error::InvalidElementClosed => None,
+            Error::InvalidElement => None,
+            #[cfg(not(comments))]
+            Error::CommentsDisabled => None,
+        }
+    }
+}
+
 impl std::fmt::Display for Error {
     fn fmt(&self, fmt: &mut std::fmt::Formatter) -> std::fmt::Result {
         match self {