From 4374966987d4a2c31514db56a67e9a4458f83909 Mon Sep 17 00:00:00 2001
From: Yuri Tseretyan <yuriy.tseretyan@grafana.com>
Date: Mon, 12 Dec 2022 10:12:30 -0500
Subject: [PATCH] Alerting: Replace hardcoded <no value> to [no value] in label
 expansion (#60129)

* replace hardcoded <no value> to [no value] in label expansion
---
 pkg/services/ngalert/state/template.go      | 11 ++++++++---
 pkg/services/ngalert/state/template_test.go | 11 ++++++-----
 2 files changed, 14 insertions(+), 8 deletions(-)

diff --git a/pkg/services/ngalert/state/template.go b/pkg/services/ngalert/state/template.go
index 3169e1b8d62..b6e8bb11a00 100644
--- a/pkg/services/ngalert/state/template.go
+++ b/pkg/services/ngalert/state/template.go
@@ -7,15 +7,17 @@ import (
 	"math"
 	"net/url"
 	"strconv"
+	"strings"
 	"time"
 
 	text_template "text/template"
 
-	"github.com/grafana/grafana/pkg/services/ngalert/eval"
 	"github.com/prometheus/common/model"
 	"github.com/prometheus/prometheus/pkg/timestamp"
 	"github.com/prometheus/prometheus/promql"
 	"github.com/prometheus/prometheus/template"
+
+	"github.com/grafana/grafana/pkg/services/ngalert/eval"
 )
 
 // templateCaptureValue represents each value in .Values in the annotations
@@ -66,8 +68,11 @@ func expandTemplate(ctx context.Context, name, text string, labels map[string]st
 			return ""
 		},
 	})
-
-	return expander.Expand()
+	result, resultErr = expander.Expand()
+	// Replace missing key value to one that does not look like an HTML tag. This can cause problems downstream in some notifiers.
+	// For example, Telegram in HTML mode rejects requests with unsupported tags.
+	result = strings.ReplaceAll(result, "<no value>", "[no value]")
+	return result, resultErr
 }
 
 func newTemplateCaptureValues(values map[string]eval.NumberValueCapture) map[string]templateCaptureValue {
diff --git a/pkg/services/ngalert/state/template_test.go b/pkg/services/ngalert/state/template_test.go
index 74ba9d64f79..398349b61c3 100644
--- a/pkg/services/ngalert/state/template_test.go
+++ b/pkg/services/ngalert/state/template_test.go
@@ -7,10 +7,11 @@ import (
 	"testing"
 
 	"github.com/grafana/grafana-plugin-sdk-go/data"
-	"github.com/grafana/grafana/pkg/services/ngalert/eval"
 	"github.com/stretchr/testify/assert"
 	"github.com/stretchr/testify/require"
 	ptr "github.com/xorcare/pointer"
+
+	"github.com/grafana/grafana/pkg/services/ngalert/eval"
 )
 
 func TestTemplateCaptureValueStringer(t *testing.T) {
@@ -57,10 +58,10 @@ func TestExpandTemplate(t *testing.T) {
 		labels:   data.Labels{"instance": "foo"},
 		expected: "foo is down",
 	}, {
-		name:     "missing label in $labels returns <no value>",
+		name:     "missing label in $labels returns [no value]",
 		text:     "{{ $labels.instance }} is down",
 		labels:   data.Labels{},
-		expected: "<no value> is down",
+		expected: "[no value] is down",
 	}, {
 		name: "values are expanded into $values",
 		text: "{{ $values.A.Labels.instance }} has value {{ $values.A }}",
@@ -88,7 +89,7 @@ func TestExpandTemplate(t *testing.T) {
 		},
 		expected: "foo has value 1.1",
 	}, {
-		name: "missing label in $values returns <no value>",
+		name: "missing label in $values returns [no value]",
 		text: "{{ $values.A.Labels.instance }} has value {{ $values.A }}",
 		alertInstance: eval.Result{
 			Values: map[string]eval.NumberValueCapture{
@@ -99,7 +100,7 @@ func TestExpandTemplate(t *testing.T) {
 				},
 			},
 		},
-		expected: "<no value> has value 1",
+		expected: "[no value] has value 1",
 	}, {
 		name: "missing value in $values is returned as NaN",
 		text: "{{ $values.A.Labels.instance }} has value {{ $values.A }}",