Fix username collision for shared channels sync update (#25578)

* fix username collision for shared channels sync update

* ensure both return types are handled

* remove unused interface

server/platform/services/sharedchannel/service.go

@@ -70,11 +70,6 @@ type errNotFound interface {
 	IsErrNotFound() bool
 }
 
-// errInvalidInput allows checking against Store.ErrInvalidInput errors without making Store a dependency.
-type errInvalidInput interface {
-	InvalidInputInfo() (entity string, field string, value any)
-}
-
 // Service provides shared channel synchronization.
 type Service struct {
 	server       ServerIface

server/platform/services/sharedchannel/sync_recv.go

@@ -248,16 +248,16 @@ func (scs *Service) insertSyncUser(user *model.User, channel *model.Channel, rc
 		user.Email = mungEmail(rc.Name, model.UserEmailMaxLength)
 
 		if userSaved, err = scs.server.GetStore().User().Save(user); err != nil {
-			e, ok := err.(errInvalidInput)
+			field, ok := isConflictError(err)
 			if !ok {
 				break
 			}
-			_, field, value := e.InvalidInputInfo()
 			if field == "email" || field == "username" {
 				// username or email collision; try again with different suffix
 				scs.server.Log().Log(mlog.LvlSharedChannelServiceWarn, "Collision inserting sync user",
 					mlog.String("field", field),
-					mlog.Any("value", value),
+					mlog.String("username", user.Username),
+					mlog.String("email", user.Email),
 					mlog.Int("attempt", i),
 					mlog.Err(err),
 				)
@@ -302,16 +302,16 @@ func (scs *Service) updateSyncUser(patch *model.UserPatch, user *model.User, cha
 		user.Email = mungEmail(rc.Name, model.UserEmailMaxLength)
 
 		if update, err = scs.server.GetStore().User().Update(user, false); err != nil {
-			e, ok := err.(errInvalidInput)
+			field, ok := isConflictError(err)
 			if !ok {
 				break
 			}
-			_, field, value := e.InvalidInputInfo()
 			if field == "email" || field == "username" {
 				// username or email collision; try again with different suffix
 				scs.server.Log().Log(mlog.LvlSharedChannelServiceWarn, "Collision updating sync user",
 					mlog.String("field", field),
-					mlog.Any("value", value),
+					mlog.String("username", user.Username),
+					mlog.String("email", user.Email),
 					mlog.Int("attempt", i),
 					mlog.Err(err),
 				)

server/platform/services/sharedchannel/util.go

@@ -4,10 +4,12 @@
 package sharedchannel
 
 import (
+	"errors"
 	"fmt"
 	"strings"
 
 	"github.com/mattermost/mattermost/server/public/model"
+	"github.com/mattermost/mattermost/server/v8/channels/store"
 )
 
 // fixMention replaces any mentions in a post for the user with the user's real username.
@@ -99,3 +101,17 @@ func mungEmail(remotename string, maxLen int) string {
 	}
 	return s
 }
+
+func isConflictError(err error) (string, bool) {
+	var errConflict *store.ErrConflict
+	if errors.As(err, &errConflict) {
+		return strings.ToLower(errConflict.Resource), true
+	}
+
+	var errInput *store.ErrInvalidInput
+	if errors.As(err, &errInput) {
+		_, field, _ := errInput.InvalidInputInfo()
+		return strings.ToLower(field), true
+	}
+	return "", false
+}