From a6cbc0c08f52bae296dafc2aea408b3a1000995e Mon Sep 17 00:00:00 2001
From: Mickael Remond <mremond@process-one.net>
Date: Wed, 19 Jun 2019 13:46:02 +0200
Subject: [PATCH] Properly decode an IQ with both a payload and an error

---
 iq.go      | 35 +++++++++++++++++++----------------
 iq_test.go | 21 +++++++++++++++++++++
 2 files changed, 40 insertions(+), 16 deletions(-)

diff --git a/iq.go b/iq.go
index 27077aa..ec165eb 100644
--- a/iq.go
+++ b/iq.go
@@ -2,6 +2,7 @@ package xmpp
 
 import (
 	"encoding/xml"
+	"fmt"
 	"strconv"
 )
 
@@ -195,7 +196,6 @@ func (iq *IQ) UnmarshalXML(d *xml.Decoder, start xml.StartElement) error {
 	}
 
 	// decode inner elements
-	level := 0
 	for {
 		t, err := d.Token()
 		if err != nil {
@@ -203,25 +203,28 @@ func (iq *IQ) UnmarshalXML(d *xml.Decoder, start xml.StartElement) error {
 		}
 
 		switch tt := t.(type) {
-
 		case xml.StartElement:
-			level++
-			if level <= 1 {
-				if iqExt := TypeRegistry.GetIQExtension(tt.Name); iqExt != nil {
-					// Decode payload extension
-					err = d.DecodeElement(iqExt, &tt)
-					if err != nil {
-						return err
-					}
-					iq.Payload = iqExt
-				} else {
-					// TODO: Fix me. We do nothing of that element here.
-					// elt = new(Node)
+			if tt.Name.Local == "error" {
+				var xmppError Err
+				err = d.DecodeElement(&xmppError, &tt)
+				if err != nil {
+					fmt.Println(err)
+					return err
 				}
+				iq.Error = xmppError
+				continue
 			}
-
+			if iqExt := TypeRegistry.GetIQExtension(tt.Name); iqExt != nil {
+				// Decode payload extension
+				err = d.DecodeElement(iqExt, &tt)
+				if err != nil {
+					return err
+				}
+				iq.Payload = iqExt
+				continue
+			}
+			return fmt.Errorf("unexpected element in iq: %s %s", tt.Name.Space, tt.Name.Local)
 		case xml.EndElement:
-			level--
 			if tt == start.End() {
 				return nil
 			}
diff --git a/iq_test.go b/iq_test.go
index 2138372..790d173 100644
--- a/iq_test.go
+++ b/iq_test.go
@@ -132,3 +132,24 @@ func TestUnmarshalPayload(t *testing.T) {
 		t.Errorf("incorrect namespace: %s", namespace)
 	}
 }
+
+func TestPayloadWithError(t *testing.T) {
+	iq := `<iq xml:lang='en' to='test1@localhost/resource' from='test@localhost' type='error' id='aac1a'>
+ <query xmlns='jabber:iq:version'/>
+ <error code='407' type='auth'>
+  <subscription-required xmlns='urn:ietf:params:xml:ns:xmpp-stanzas'/>
+  <text xml:lang='en' xmlns='urn:ietf:params:xml:ns:xmpp-stanzas'>Not subscribed</text>
+ </error>
+</iq>`
+
+	parsedIQ := xmpp.IQ{}
+	err := xml.Unmarshal([]byte(iq), &parsedIQ)
+	if err != nil {
+		t.Errorf("Unmarshal error: %s", iq)
+		return
+	}
+
+	if parsedIQ.Error.Reason != "subscription-required" {
+		t.Errorf("incorrect error value: '%s'", parsedIQ.Error.Reason)
+	}
+}