avoid HTMLString and render placeholder in template

routers/web/repo/editor.go

@@ -420,10 +420,10 @@ func DiffPreviewPost(ctx *context.Context) {
 	}
 
 	if diff.NumFiles == 0 {
-		ctx.HTMLString(http.StatusOK, `<div class="tw-p-6">`+ctx.Locale.TrString("repo.editor.no_changes_to_show")+`</div>`)
-		return
-	}
+		ctx.Data["File"] = nil
+	} else {
 		ctx.Data["File"] = diff.Files[0]
+	}
 
 	ctx.HTML(http.StatusOK, tplEditDiffPreview)
 }

services/context/base.go

@@ -137,15 +137,6 @@ func (b *Base) JSON(status int, content any) {
 	}
 }
 
-// HTMLString renders string as HTML
-func (b *Base) HTMLString(status int, html string) {
-	b.Resp.Header().Set("Content-Type", "text/html;charset=utf-8")
-	b.Resp.WriteHeader(status)
-	if _, err := b.Resp.Write([]byte(html)); err != nil {
-		log.Error("Render HTMLString failed: %v", err)
-	}
-}
-
 // RemoteAddr returns the client machine ip address
 func (b *Base) RemoteAddr() string {
 	return b.Req.RemoteAddr

templates/repo/editor/diff_preview.tmpl

@@ -1,3 +1,4 @@
+{{if .File}}
 <div class="diff-file-box">
 	<div class="ui attached table segment">
 		<div class="file-body file-code code-diff code-diff-unified unicode-escaped">
@@ -9,3 +10,8 @@
 		</div>
 	</div>
 </div>
+{{else}}
+<div class="tw-p-6">
+	{{ctx.Locale.Tr "repo.editor.no_changes_to_show"}}
+</div>
+{{end}}