Fix listobjects with metadata

`UserMetadata` did not match actual format sent.

Change type of `UserTags`, so it can be unmarshaled from XML string.

Tested with mc.

api-datatypes.go

@@ -21,6 +21,8 @@ import (
 	"encoding/xml"
 	"io"
 	"net/http"
+	"net/url"
+	"strings"
 	"time"
 )
 
@@ -43,26 +45,78 @@ type StringMap map[string]string
 // if m is nil it can be initialized, which is often the case if m is
 // nested in another xml structural. This is also why the first thing done
 // on the first line is initialize it.
-func (m *StringMap) UnmarshalXML(d *xml.Decoder, _ xml.StartElement) error {
+func (m *StringMap) UnmarshalXML(d *xml.Decoder, s xml.StartElement) error {
 	*m = StringMap{}
-	type Item struct {
-		Key   string
-		Value string
-	}
 	for {
-		var e Item
+		// Format is <key>value</key>
+		var e struct {
+			XMLName xml.Name
+			Value   string `xml:",chardata"`
+		}
 		err := d.Decode(&e)
 		if err == io.EOF {
 			break
 		}
 		if err != nil {
 			return err
 		}
-		(*m)[e.Key] = e.Value
+		(*m)[e.XMLName.Local] = e.Value
 	}
 	return nil
 }
 
+// URLMap represents map with custom UnmarshalXML
+type URLMap map[string]string
+
+// UnmarshalXML unmarshals the XML into a map of string to strings,
+// creating a key in the map for each tag and setting it's value to the
+// tags contents.
+//
+// The fact this function is on the pointer of Map is important, so that
+// if m is nil it can be initialized, which is often the case if m is
+// nested in another xml structural. This is also why the first thing done
+// on the first line is initialize it.
+func (m *URLMap) UnmarshalXML(d *xml.Decoder, se xml.StartElement) error {
+	*m = URLMap{}
+	var tgs string
+	if err := d.DecodeElement(&tgs, &se); err != nil {
+		if err == io.EOF {
+			return nil
+		}
+		return err
+	}
+	for tgs != "" {
+		var key string
+		key, tgs, _ = stringsCut(tgs, "&")
+		if key == "" {
+			continue
+		}
+		key, value, _ := stringsCut(key, "=")
+		key, err := url.QueryUnescape(key)
+		if err != nil {
+			return err
+		}
+
+		value, err = url.QueryUnescape(value)
+		if err != nil {
+			return err
+		}
+		(*m)[key] = value
+	}
+	return nil
+}
+
+// stringsCut slices s around the first instance of sep,
+// returning the text before and after sep.
+// The found result reports whether sep appears in s.
+// If sep does not appear in s, cut returns s, "", false.
+func stringsCut(s, sep string) (before, after string, found bool) {
+	if i := strings.Index(s, sep); i >= 0 {
+		return s[:i], s[i+len(sep):], true
+	}
+	return s, "", false
+}
+
 // Owner name.
 type Owner struct {
 	XMLName     xml.Name `xml:"Owner" json:"owner"`
@@ -124,7 +178,7 @@ type ObjectInfo struct {
 	UserMetadata StringMap `json:"userMetadata,omitempty"`
 
 	// x-amz-tagging values in their k/v values.
-	UserTags map[string]string `json:"userTags"`
+	UserTags URLMap `json:"userTags" xml:"UserTags"`
 
 	// x-amz-tagging-count value
 	UserTagCount int