[release-12.0.2] Alerting: Fix $value type when single data source is queried (#106101)

Alerting: Fix $value type when single data source is queried (#106080)

(cherry picked from commit faeddf334a)

Co-authored-by: Alexander Akhmetov <me@alx.cx>

pkg/services/ngalert/state/template/template.go

@@ -77,18 +77,18 @@ type Data struct {
 	Values map[string]Value
 
 	// Value is the .Value and $value variables in templates.
-	// For single datasource queries, this will be the numeric value of the query.
-	// For multiple datasource queries, this will be the evaluation string.
-	Value string
+	// For single datasource queries, this will be the numeric value of the query (float64).
+	// For multiple datasource queries, this will be the evaluation string (string).
+	Value any
 }
 
 func NewData(labels map[string]string, res eval.Result) Data {
 	values := NewValues(res.Values)
 
 	// By default, use the evaluation string as the Value
-	valueStr := res.EvaluationString
+	var value any = res.EvaluationString
 
-	// If there's exactly one datasource node, use its value instead
+	// If there's exactly one datasource node, use its numeric value instead
 	// This makes the $value variable compatible with Prometheus templating
 	// where $value holds the numeric value of the alert query
 	datasourceNodeCount := 0
@@ -105,13 +105,13 @@ func NewData(labels map[string]string, res eval.Result) Data {
 	}
 
 	if datasourceNodeCount == 1 {
-		valueStr = datasourceNodeValue.String()
+		value = datasourceNodeValue.Value
 	}
 
 	return Data{
 		Labels: labels,
 		Values: values,
-		Value:  valueStr,
+		Value:  value,
 	}
 }
 

pkg/services/ngalert/state/template/template_test.go

@@ -3,6 +3,7 @@ package template
 import (
 	"context"
 	"errors"
+	"math"
 	"net/url"
 	"testing"
 
@@ -109,7 +110,7 @@ func TestNewData(t *testing.T) {
 		}
 
 		data := NewData(map[string]string{}, res)
-		assert.Equal(t, "10", data.Value)
+		assert.Equal(t, 10.0, data.Value)
 	})
 
 	t.Run("uses evaluation string when multiple datasource nodes exist", func(t *testing.T) {
@@ -159,7 +160,7 @@ func TestDatasourceValueInTemplating(t *testing.T) {
 
 		data := NewData(map[string]string{}, res)
 		// In Prometheus, a nil value would be rendered as NaN
-		assert.Equal(t, "NaN", data.Value)
+		assert.True(t, math.IsNaN(data.Value.(float64)))
 	})
 
 	t.Run("single datasource node uses query value", func(t *testing.T) {
@@ -188,7 +189,7 @@ func TestDatasourceValueInTemplating(t *testing.T) {
 		}
 
 		data := NewData(map[string]string{}, res)
-		assert.Equal(t, "10", data.Value)
+		assert.Equal(t, 10.0, data.Value)
 	})
 
 	t.Run("multiple datasource nodes uses evaluation string", func(t *testing.T) {
@@ -636,8 +637,56 @@ func TestExpandTemplate(t *testing.T) {
 		name:     "check that safeHtml doesn't error or panic",
 		text:     "{{ \"<b>\" | safeHtml }}",
 		expected: "<b>",
-	},
-	}
+	}, {
+		name: "$value numeric comparison with single datasource",
+		text: `{{ if eq $value 1.0 }}equal{{ else }}not equal{{ end }}`,
+		alertInstance: eval.Result{
+			Values: map[string]eval.NumberValueCapture{
+				"A": {
+					Var:              "A",
+					IsDatasourceNode: true,
+					Labels:           data.Labels{"instance": "foo"},
+					Value:            util.Pointer(1.0),
+				},
+			},
+		},
+		expected: "equal",
+	}, {
+		name: "humanize with string $value (multiple datasources)",
+		text: `{{ humanize $value }}`,
+		alertInstance: eval.Result{
+			EvaluationString: "1234567.0",
+			Values: map[string]eval.NumberValueCapture{
+				"A": {
+					Var:              "A",
+					IsDatasourceNode: true,
+					Labels:           data.Labels{"instance": "foo"},
+					Value:            util.Pointer(10.0),
+				},
+				"B": {
+					Var:              "B",
+					IsDatasourceNode: true,
+					Labels:           data.Labels{"instance": "bar"},
+					Value:            util.Pointer(20.0),
+				},
+			},
+		},
+		expected: "1.235M",
+	}, {
+		name: "humanize with numeric $value (single datasource)",
+		text: `{{ humanize $value }}`,
+		alertInstance: eval.Result{
+			Values: map[string]eval.NumberValueCapture{
+				"A": {
+					Var:              "A",
+					IsDatasourceNode: true,
+					Labels:           data.Labels{"instance": "foo"},
+					Value:            util.Pointer(1234567.0),
+				},
+			},
+		},
+		expected: "1.235M",
+	}}
 
 	for _, c := range cases {
 		t.Run(c.name, func(t *testing.T) {