ocdav: Fix parsing of PROPPATCH properties (#743)

Use the parent struct when parsing to make sure the decoder finds the
hint about "innerxml" parsing mode for proppatch properties,
and prevents mangling of said values when they contain an "xmlns"
attribute.

internal/http/services/owncloud/ocdav/proppatch.go

@@ -19,7 +19,6 @@
 package ocdav
 
 import (
-	"bytes"
 	"encoding/xml"
 	"fmt"
 	"io"
@@ -213,35 +212,6 @@ type Proppatch struct {
 	Props []propertyXML
 }
 
-type xmlValue []byte
-
-func (v *xmlValue) UnmarshalXML(d *xml.Decoder, start xml.StartElement) error {
-	// The XML value of a property can be arbitrary, mixed-content XML.
-	// To make sure that the unmarshalled value contains all required
-	// namespaces, we encode all the property value XML tokens into a
-	// buffer. This forces the encoder to redeclare any used namespaces.
-	var b bytes.Buffer
-	e := xml.NewEncoder(&b)
-	for {
-		t, err := next(d)
-		if err != nil {
-			return err
-		}
-		if e, ok := t.(xml.EndElement); ok && e.Name == start.Name {
-			break
-		}
-		if err = e.EncodeToken(t); err != nil {
-			return err
-		}
-	}
-	err := e.Flush()
-	if err != nil {
-		return err
-	}
-	*v = b.Bytes()
-	return nil
-}
-
 // http://www.webdav.org/specs/rfc4918.html#ELEMENT_prop (for proppatch)
 type proppatchProps []propertyXML
 
@@ -267,14 +237,13 @@ func (ps *proppatchProps) UnmarshalXML(d *xml.Decoder, start xml.StartElement) e
 			}
 			return nil
 		case xml.StartElement:
-			p := propertyXML{
-				XMLName: t.(xml.StartElement).Name,
-				Lang:    xmlLang(t.(xml.StartElement), lang),
-			}
-			err = d.DecodeElement(((*xmlValue)(&p.InnerXML)), &elem)
+			p := propertyXML{}
+			err = d.DecodeElement(&p, &elem)
 			if err != nil {
 				return err
 			}
+			// special handling for the lang property
+			p.Lang = xmlLang(t.(xml.StartElement), lang)
 			*ps = append(*ps, p)
 		}
 	}