Clean up template locale usage (#27856)

After many refactoring PRs for the "locale" and "template context
function", now the ".locale" is not needed for web templates any more.

This PR does a clean up for:

1. Remove `ctx.Data["locale"]` for web context.
2. Use `ctx.Locale` in `500.tmpl`, for consistency.
3. Add a test check for `500 page` locale usage.
4. Remove the `Str2html` and `DotEscape` from mail template context
data, they are copy&paste errors introduced by #19169 and #16200 . These
functions are template functions (provided by the common renderer), but
not template data variables.
5. Make email `SendAsync` function mockable (I was planning to add more
tests but it would make this PR much too complex, so the tests could be
done in another PR)

6 files changed, 15 insertions, 46 deletions

diff --git a/services/mailer/mail.go b/services/mailer/mail.go
index 0210128046..1f139d233f 100644
--- a/services/mailer/mail.go
+++ b/services/mailer/mail.go
@@ -26,7 +26,6 @@ import (
 	"code.gitea.io/gitea/modules/markup"
 	"code.gitea.io/gitea/modules/markup/markdown"
 	"code.gitea.io/gitea/modules/setting"
-	"code.gitea.io/gitea/modules/templates"
 	"code.gitea.io/gitea/modules/timeutil"
 	"code.gitea.io/gitea/modules/translation"
 	incoming_payload "code.gitea.io/gitea/services/mailer/incoming/payload"
@@ -68,15 +67,12 @@ func SendTestMail(email string) error {
 func sendUserMail(language string, u *user_model.User, tpl base.TplName, code, subject, info string) {
 	locale := translation.NewLocale(language)
 	data := map[string]any{
+		"locale":            locale,
 		"DisplayName":       u.DisplayName(),
 		"ActiveCodeLives":   timeutil.MinutesToFriendly(setting.Service.ActiveCodeLives, locale),
 		"ResetPwdCodeLives": timeutil.MinutesToFriendly(setting.Service.ResetPwdCodeLives, locale),
 		"Code":              code,
 		"Language":          locale.Language(),
-		// helper
-		"locale":    locale,
-		"Str2html":  templates.Str2html,
-		"DotEscape": templates.DotEscape,
 	}
 
 	var content bytes.Buffer
@@ -119,15 +115,12 @@ func SendActivateEmailMail(u *user_model.User, email *user_model.EmailAddress) {
 	}
 	locale := translation.NewLocale(u.Language)
 	data := map[string]any{
+		"locale":          locale,
 		"DisplayName":     u.DisplayName(),
 		"ActiveCodeLives": timeutil.MinutesToFriendly(setting.Service.ActiveCodeLives, locale),
 		"Code":            u.GenerateEmailActivateCode(email.Email),
 		"Email":           email.Email,
 		"Language":        locale.Language(),
-		// helper
-		"locale":    locale,
-		"Str2html":  templates.Str2html,
-		"DotEscape": templates.DotEscape,
 	}
 
 	var content bytes.Buffer
@@ -152,13 +145,10 @@ func SendRegisterNotifyMail(u *user_model.User) {
 	locale := translation.NewLocale(u.Language)
 
 	data := map[string]any{
+		"locale":      locale,
 		"DisplayName": u.DisplayName(),
 		"Username":    u.Name,
 		"Language":    locale.Language(),
-		// helper
-		"locale":    locale,
-		"Str2html":  templates.Str2html,
-		"DotEscape": templates.DotEscape,
 	}
 
 	var content bytes.Buffer
@@ -185,14 +175,11 @@ func SendCollaboratorMail(u, doer *user_model.User, repo *repo_model.Repository)
 
 	subject := locale.Tr("mail.repo.collaborator.added.subject", doer.DisplayName(), repoName)
 	data := map[string]any{
+		"locale":   locale,
 		"Subject":  subject,
 		"RepoName": repoName,
 		"Link":     repo.HTMLURL(),
 		"Language": locale.Language(),
-		// helper
-		"locale":    locale,
-		"Str2html":  templates.Str2html,
-		"DotEscape": templates.DotEscape,
 	}
 
 	var content bytes.Buffer
@@ -259,6 +246,7 @@ func composeIssueCommentMessages(ctx *mailCommentContext, lang string, recipient
 	locale := translation.NewLocale(lang)
 
 	mailMeta := map[string]any{
+		"locale":          locale,
 		"FallbackSubject": fallback,
 		"Body":            body,
 		"Link":            link,
@@ -275,10 +263,6 @@ func composeIssueCommentMessages(ctx *mailCommentContext, lang string, recipient
 		"ReviewComments":  reviewComments,
 		"Language":        locale.Language(),
 		"CanReply":        setting.IncomingEmail.Enabled && commentType != issues_model.CommentTypePullRequestPush,
-		// helper
-		"locale":    locale,
-		"Str2html":  templates.Str2html,
-		"DotEscape": templates.DotEscape,
 	}
 
 	var mailSubject bytes.Buffer
@@ -469,7 +453,7 @@ func SendIssueAssignedMail(ctx context.Context, issue *issues_model.Issue, doer
 		if err != nil {
 			return err
 		}
-		SendAsyncs(msgs)
+		SendAsync(msgs...)
 	}
 	return nil
 }
diff --git a/services/mailer/mail_issue.go b/services/mailer/mail_issue.go
index baa9f1d9ab..fab3315be2 100644
--- a/services/mailer/mail_issue.go
+++ b/services/mailer/mail_issue.go
@@ -162,7 +162,7 @@ func mailIssueCommentBatch(ctx *mailCommentContext, users []*user_model.User, vi
 			if err != nil {
 				return err
 			}
-			SendAsyncs(msgs)
+			SendAsync(msgs...)
 			receivers = receivers[:i]
 		}
 	}
diff --git a/services/mailer/mail_release.go b/services/mailer/mail_release.go
index 7bc3db3fe6..88973a6be2 100644
--- a/services/mailer/mail_release.go
+++ b/services/mailer/mail_release.go
@@ -14,7 +14,6 @@ import (
 	"code.gitea.io/gitea/modules/markup"
 	"code.gitea.io/gitea/modules/markup/markdown"
 	"code.gitea.io/gitea/modules/setting"
-	"code.gitea.io/gitea/modules/templates"
 	"code.gitea.io/gitea/modules/translation"
 )
 
@@ -69,13 +68,10 @@ func mailNewRelease(ctx context.Context, lang string, tos []string, rel *repo_mo
 
 	subject := locale.Tr("mail.release.new.subject", rel.TagName, rel.Repo.FullName())
 	mailMeta := map[string]any{
+		"locale":   locale,
 		"Release":  rel,
 		"Subject":  subject,
 		"Language": locale.Language(),
-		// helper
-		"locale":    locale,
-		"Str2html":  templates.Str2html,
-		"DotEscape": templates.DotEscape,
 	}
 
 	var mailBody bytes.Buffer
@@ -95,5 +91,5 @@ func mailNewRelease(ctx context.Context, lang string, tos []string, rel *repo_mo
 		msgs = append(msgs, msg)
 	}
 
-	SendAsyncs(msgs)
+	SendAsync(msgs...)
 }
diff --git a/services/mailer/mail_repo.go b/services/mailer/mail_repo.go
index e9c1991b5b..b89dcd43b5 100644
--- a/services/mailer/mail_repo.go
+++ b/services/mailer/mail_repo.go
@@ -12,7 +12,6 @@ import (
 	repo_model "code.gitea.io/gitea/models/repo"
 	user_model "code.gitea.io/gitea/models/user"
 	"code.gitea.io/gitea/modules/setting"
-	"code.gitea.io/gitea/modules/templates"
 	"code.gitea.io/gitea/modules/translation"
 )
 
@@ -65,6 +64,7 @@ func sendRepoTransferNotifyMailPerLang(lang string, newOwner, doer *user_model.U
 	}
 
 	data := map[string]any{
+		"locale":      locale,
 		"Doer":        doer,
 		"User":        repo.Owner,
 		"Repo":        repo.FullName(),
@@ -72,10 +72,6 @@ func sendRepoTransferNotifyMailPerLang(lang string, newOwner, doer *user_model.U
 		"Subject":     subject,
 		"Language":    locale.Language(),
 		"Destination": destination,
-		// helper
-		"locale":    locale,
-		"Str2html":  templates.Str2html,
-		"DotEscape": templates.DotEscape,
 	}
 
 	if err := bodyTemplates.ExecuteTemplate(&content, string(mailRepoTransferNotify), data); err != nil {
diff --git a/services/mailer/mail_team_invite.go b/services/mailer/mail_team_invite.go
index 88ad0c9836..ab32beefac 100644
--- a/services/mailer/mail_team_invite.go
+++ b/services/mailer/mail_team_invite.go
@@ -14,7 +14,6 @@ import (
 	"code.gitea.io/gitea/modules/base"
 	"code.gitea.io/gitea/modules/log"
 	"code.gitea.io/gitea/modules/setting"
-	"code.gitea.io/gitea/modules/templates"
 	"code.gitea.io/gitea/modules/translation"
 )
 
@@ -53,16 +52,13 @@ func MailTeamInvite(ctx context.Context, inviter *user_model.User, team *org_mod
 
 	subject := locale.Tr("mail.team_invite.subject", inviter.DisplayName(), org.DisplayName())
 	mailMeta := map[string]any{
+		"locale":       locale,
 		"Inviter":      inviter,
 		"Organization": org,
 		"Team":         team,
 		"Invite":       invite,
 		"Subject":      subject,
 		"InviteURL":    inviteURL,
-		// helper
-		"locale":    locale,
-		"Str2html":  templates.Str2html,
-		"DotEscape": templates.DotEscape,
 	}
 
 	var mailBody bytes.Buffer
diff --git a/services/mailer/mailer.go b/services/mailer/mailer.go
index 42d7d5ad5d..5e8e3dbb38 100644
--- a/services/mailer/mailer.go
+++ b/services/mailer/mailer.go
@@ -425,15 +425,12 @@ func NewContext(ctx context.Context) {
 	go graceful.GetManager().RunWithCancel(mailQueue)
 }
 
-// SendAsync send mail asynchronously
-func SendAsync(msg *Message) {
-	SendAsyncs([]*Message{msg})
-}
+// SendAsync send emails asynchronously (make it mockable)
+var SendAsync = sendAsync
 
-// SendAsyncs send mails asynchronously
-func SendAsyncs(msgs []*Message) {
+func sendAsync(msgs ...*Message) {
 	if setting.MailService == nil {
-		log.Error("Mailer: SendAsyncs is being invoked but mail service hasn't been initialized")
+		log.Error("Mailer: SendAsync is being invoked but mail service hasn't been initialized")
 		return
 	}