Feat: replace cred when refreshing non-singleton credential

attributes.go

@@ -63,6 +63,22 @@ func (al *AttributeList) Info() *CredentialInfo {
 	return al.info
 }
 
+// EqualsExceptMetadata checks whether two AttributeLists have the same attribute values.
+// The attribute containing the metadata information is skipped in this check.
+func (al *AttributeList) EqualsExceptMetadata(ol *AttributeList) bool {
+	if len(al.Ints) != len(ol.Ints) {
+		return false
+	}
+
+	// Check whether value of all attributes, except for metadata attribute, is equal
+	for i := 1; i < len(al.Ints); i++ {
+		if al.Ints[i].Cmp(ol.Ints[i]) != 0 {
+			return false
+		}
+	}
+	return true
+}
+
 func (al *AttributeList) Hash() string {
 	if al.h == "" {
 		bytes := []byte{}

internal/sessiontest/session_test.go

@@ -96,6 +96,20 @@ func TestIssuanceOptionalSetAttributes(t *testing.T) {
 	sessionHelper(t, req, "issue", nil)
 }
 
+func TestIssuanceSameAttributesNotSingleton(t *testing.T) {
+	client, _ := parseStorage(t)
+	defer test.ClearTestStorage(t)
+
+	prevLen := len(client.CredentialInfoList())
+
+	req := getIssuanceRequest(true)
+	sessionHelper(t, req, "issue", client)
+
+	req = getIssuanceRequest(false)
+	sessionHelper(t, req, "issue", client)
+	require.Equal(t, prevLen+1, len(client.CredentialInfoList()))
+}
+
 func TestLargeAttribute(t *testing.T) {
 	client, _ := parseStorage(t)
 	defer test.ClearTestStorage(t)

irmaclient/client.go

@@ -217,9 +217,18 @@ func (client *Client) addCredential(cred *credential, storeAttributes bool) (err
 	}
 
 	// If this is a singleton credential type, ensure we have at most one by removing any previous instance
-	if !id.Empty() && cred.CredentialType().IsSingleton {
+	// If a credential already exists with exactly the same attribute values (except metadata), delete the previous credential
+	if !id.Empty() {
+		if cred.CredentialType().IsSingleton {
 			for len(client.attrs(id)) != 0 {
-			client.remove(id, 0, false)
+				_ = client.remove(id, 0, false)
+			}
+		}
+
+		for i := len(client.attrs(id)) - 1; i >= 0; i-- { // Go backwards through array because remove manipulates it
+			if client.attrs(id)[i].EqualsExceptMetadata(cred.AttributeList()) {
+				_ = client.remove(id, i, false)
+			}
 		}
 	}