Replace -1 with GhostUserID (#27703)

models/user/avatar.go

@@ -58,8 +58,7 @@ func GenerateRandomAvatar(ctx context.Context, u *User) error {
 
 // AvatarLinkWithSize returns a link to the user's avatar with size. size <= 0 means default size
 func (u *User) AvatarLinkWithSize(ctx context.Context, size int) string {
-	if u.ID == -1 {
-		// ghost user
+	if u.IsGhost() {
 		return avatars.DefaultAvatarLink()
 	}
 

models/user/user.go

@@ -933,7 +933,7 @@ func GetUserByIDs(ctx context.Context, ids []int64) ([]*User, error) {
 // GetPossibleUserByID returns the user if id > 0 or return system usrs if id < 0
 func GetPossibleUserByID(ctx context.Context, id int64) (*User, error) {
 	switch id {
-	case -1:
+	case GhostUserID:
 		return NewGhostUser(), nil
 	case ActionsUserID:
 		return NewActionsUser(), nil
@@ -949,7 +949,7 @@ func GetPossibleUserByIDs(ctx context.Context, ids []int64) ([]*User, error) {
 	uniqueIDs := container.SetOf(ids...)
 	users := make([]*User, 0, len(ids))
 	_ = uniqueIDs.Remove(0)
-	if uniqueIDs.Remove(-1) {
+	if uniqueIDs.Remove(GhostUserID) {
 		users = append(users, NewGhostUser())
 	}
 	if uniqueIDs.Remove(ActionsUserID) {

models/user/user_system.go

@@ -9,12 +9,18 @@ import (
 	"code.gitea.io/gitea/modules/structs"
 )
 
+const (
+	GhostUserID        = -1
+	GhostUserName      = "Ghost"
+	GhostUserLowerName = "ghost"
+)
+
 // NewGhostUser creates and returns a fake user for someone has deleted their account.
 func NewGhostUser() *User {
 	return &User{
-		ID:        -1,
-		Name:      "Ghost",
-		LowerName: "ghost",
+		ID:        GhostUserID,
+		Name:      GhostUserName,
+		LowerName: GhostUserLowerName,
 	}
 }
 
@@ -23,13 +29,13 @@ func (u *User) IsGhost() bool {
 	if u == nil {
 		return false
 	}
-	return u.ID == -1 && u.Name == "Ghost"
+	return u.ID == GhostUserID && u.Name == GhostUserName
 }
 
 // NewReplaceUser creates and returns a fake user for external user
 func NewReplaceUser(name string) *User {
 	return &User{
-		ID:        -1,
+		ID:        0,
 		Name:      name,
 		LowerName: strings.ToLower(name),
 	}