From 85f9735978433c9d49a24f51fa76b28f45beeb7c Mon Sep 17 00:00:00 2001
From: Michal 'vorner' Vaner <vorner@vorner.cz>
Date: Sun, 30 Dec 2018 19:06:28 +0100
Subject: Tracking a path where an error happens during deserialization

Related to #83, but doesn't solve that specific problem :-(. That
specific error message ("missing field") comes from somewhere else than
this library.
---
 src/de.rs | 15 +++++++++++----
 1 file changed, 11 insertions(+), 4 deletions(-)

(limited to 'src/de.rs')

diff --git a/src/de.rs b/src/de.rs
index 9ebe2e4..9267338 100644
--- a/src/de.rs
+++ b/src/de.rs
@@ -2,6 +2,7 @@ use config::Config;
 use error::*;
 use serde::de;
 use std::collections::{HashMap, VecDeque};
+use std::iter::Enumerate;
 use value::{Value, ValueKind, ValueWithKey, Table};
 
 // TODO: Use a macro or some other magic to reduce the code duplication here
@@ -284,13 +285,13 @@ impl<'de, 'a> de::Deserializer<'de> for StrDeserializer<'a> {
 }
 
 struct SeqAccess {
-    elements: ::std::vec::IntoIter<Value>,
+    elements: Enumerate<::std::vec::IntoIter<Value>>,
 }
 
 impl SeqAccess {
     fn new(elements: Vec<Value>) -> Self {
         SeqAccess {
-            elements: elements.into_iter(),
+            elements: elements.into_iter().enumerate(),
         }
     }
 }
@@ -303,7 +304,11 @@ impl<'de> de::SeqAccess<'de> for SeqAccess {
         T: de::DeserializeSeed<'de>,
     {
         match self.elements.next() {
-            Some(value) => seed.deserialize(value).map(Some),
+            Some((idx, value)) => {
+                seed.deserialize(value)
+                    .map(Some)
+                    .map_err(|e| e.prepend_index(idx))
+            }
             None => Ok(None),
         }
     }
@@ -349,7 +354,9 @@ impl<'de> de::MapAccess<'de> for MapAccess {
     where
         V: de::DeserializeSeed<'de>,
     {
-        de::DeserializeSeed::deserialize(seed, self.elements.pop_front().unwrap().1)
+        let (key, value) = self.elements.pop_front().unwrap();
+        de::DeserializeSeed::deserialize(seed, value)
+            .map_err(|e| e.prepend_key(key))
     }
 }
 
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