Add missing mail notification

modules/notification/mail/mail.go

@@ -8,6 +8,7 @@ import (
 	"fmt"
 
 	"code.gitea.io/gitea/models"
+	"code.gitea.io/gitea/modules/git"
 	"code.gitea.io/gitea/modules/log"
 	"code.gitea.io/gitea/modules/notification/base"
 	"code.gitea.io/gitea/services/mailer"
@@ -98,3 +99,14 @@ func (m *mailNotifier) NotifyIssueChangeAssignee(doer *models.User, issue *model
 		mailer.SendIssueAssignedMail(issue, doer, ct, comment, []string{assignee.Email})
 	}
 }
+
+func (m *mailNotifier) NotifyMergePullRequest(pr *models.PullRequest, doer *models.User, baseRepo *git.Repository) {
+	if err := pr.LoadIssue(); err != nil {
+		log.Error("pr.LoadIssue: %v", err)
+		return
+	}
+
+	if err := mailer.MailParticipants(pr.Issue, doer, models.ActionClosePullRequest); err != nil {
+		log.Error("MailParticipants: %v", err)
+	}
+}

routers/repo/pull.go

@@ -716,8 +716,6 @@ func MergePullRequest(ctx *context.Context, form auth.MergePullRequestForm) {
 		return
 	}
 
-	notification.NotifyMergePullRequest(pr, ctx.User, ctx.Repo.GitRepo)
-
 	log.Trace("Pull request merged: %d", pr.ID)
 	ctx.Redirect(ctx.Repo.RepoLink + "/pulls/" + com.ToStr(pr.Index))
 }