Alerting: Don't include image_url field with Slack message if empty (#22372)

pkg/services/alerting/notifiers/slack.go

@@ -276,22 +276,25 @@ func (sn *SlackNotifier) Notify(evalContext *alerting.EvalContext) error {
 			},
 			},
 		}
 		}
 	}
 	}
-	body := map[string]interface{}{
-		"text":   evalContext.GetNotificationTitle(),
-		"blocks": blocks,
-		"attachments": []map[string]interface{}{
-			{
+	attachment := map[string]interface{}{
 		"color":       evalContext.GetStateModel().Color,
 		"color":       evalContext.GetStateModel().Color,
 		"title":       evalContext.GetNotificationTitle(),
 		"title":       evalContext.GetNotificationTitle(),
 		"title_link":  ruleURL,
 		"title_link":  ruleURL,
 		"text":        msg,
 		"text":        msg,
 		"fallback":    evalContext.GetNotificationTitle(),
 		"fallback":    evalContext.GetNotificationTitle(),
 		"fields":      fields,
 		"fields":      fields,
-				"image_url":   imageURL,
 		"footer":      "Grafana v" + setting.BuildVersion,
 		"footer":      "Grafana v" + setting.BuildVersion,
 		"footer_icon": "https://grafana.com/assets/img/fav32.png",
 		"footer_icon": "https://grafana.com/assets/img/fav32.png",
 		"ts":          time.Now().Unix(),
 		"ts":          time.Now().Unix(),
-			},
+	}
+	if imageURL != "" {
+		attachment["image_url"] = imageURL
+	}
+	body := map[string]interface{}{
+		"text":   evalContext.GetNotificationTitle(),
+		"blocks": blocks,
+		"attachments": []map[string]interface{}{
+			attachment,
 		},
 		},
 		"parse": "full", // to linkify urls, users and channels in alert message.
 		"parse": "full", // to linkify urls, users and channels in alert message.
 	}
 	}
@@ -313,6 +316,7 @@ func (sn *SlackNotifier) Notify(evalContext *alerting.EvalContext) error {
 	if err != nil {
 	if err != nil {
 		return err
 		return err
 	}
 	}
+
 	cmd := &models.SendWebhookSync{Url: sn.URL, Body: string(data)}
 	cmd := &models.SendWebhookSync{Url: sn.URL, Body: string(data)}
 	if err := bus.DispatchCtx(evalContext.Ctx, cmd); err != nil {
 	if err := bus.DispatchCtx(evalContext.Ctx, cmd); err != nil {
 		sn.log.Error("Failed to send slack notification", "error", err, "webhook", sn.Name)
 		sn.log.Error("Failed to send slack notification", "error", err, "webhook", sn.Name)