add settings.UI.ReactionsMap

so if !setting.UI.ReactionsMap[opts.Type] works

models/issue_reaction.go

@@ -10,7 +10,6 @@ import (
 
 	"code.gitea.io/gitea/modules/setting"
 	"code.gitea.io/gitea/modules/timeutil"
-	"code.gitea.io/gitea/modules/util"
 
 	"xorm.io/builder"
 	"xorm.io/xorm"
@@ -100,7 +99,7 @@ type ReactionOptions struct {
 
 // CreateReaction creates reaction for issue or comment.
 func CreateReaction(opts *ReactionOptions) (reaction *Reaction, err error) {
-	if !util.IsStringInSlice(opts.Type, setting.UI.Reactions) {
+	if !setting.UI.ReactionsMap[opts.Type] {
 		return nil, ErrForbiddenIssueReaction{opts.Type}
 	}
 

modules/setting/setting.go

@@ -171,6 +171,7 @@ var (
 		DefaultTheme          string
 		Themes                []string
 		Reactions             []string
+		ReactionsMap          map[string]bool
 		SearchRepoDescription bool
 		UseServiceWorker      bool
 
@@ -985,6 +986,11 @@ func NewContext() {
 	U2F.AppID = sec.Key("APP_ID").MustString(strings.TrimRight(AppURL, "/"))
 
 	zip.Verbose = false
+
+	UI.ReactionsMap = make(map[string]bool)
+	for _, reaction := range UI.Reactions {
+		UI.ReactionsMap[reaction] = true
+	}
 }
 
 func loadInternalToken(sec *ini.Section) string {