From 4b417c8f3e7d77b6d790d77432bb8e60f634fdef Mon Sep 17 00:00:00 2001
From: Yuriy Tseretyan <yuriy.tseretyan@grafana.com>
Date: Wed, 27 Apr 2022 14:59:13 -0400
Subject: [PATCH] use NaN if condition value is nil (#48370)

---
 pkg/services/ngalert/state/state.go      |  7 ++-
 pkg/services/ngalert/state/state_test.go | 75 ++++++++++++++++++++++++
 2 files changed, 81 insertions(+), 1 deletion(-)

diff --git a/pkg/services/ngalert/state/state.go b/pkg/services/ngalert/state/state.go
index cf5c5b849d2..4684c70cce8 100644
--- a/pkg/services/ngalert/state/state.go
+++ b/pkg/services/ngalert/state/state.go
@@ -3,6 +3,7 @@ package state
 import (
 	"errors"
 	"fmt"
+	"math"
 	"strings"
 	"time"
 
@@ -223,7 +224,11 @@ func (a *State) GetLastEvaluationValuesForCondition() map[string]float64 {
 
 	for refID, value := range lastResult.Values {
 		if strings.Contains(refID, lastResult.Condition) {
-			r[refID] = *value
+			if value != nil {
+				r[refID] = *value
+				continue
+			}
+			r[refID] = math.NaN()
 		}
 	}
 
diff --git a/pkg/services/ngalert/state/state_test.go b/pkg/services/ngalert/state/state_test.go
index b5a3ee1e54d..d1d455f56ce 100644
--- a/pkg/services/ngalert/state/state_test.go
+++ b/pkg/services/ngalert/state/state_test.go
@@ -1,10 +1,14 @@
 package state
 
 import (
+	"math"
 	"math/rand"
 	"testing"
 	"time"
 
+	"github.com/stretchr/testify/require"
+	ptr "github.com/xorcare/pointer"
+
 	"github.com/grafana/grafana/pkg/services/ngalert/eval"
 	ngmodels "github.com/grafana/grafana/pkg/services/ngalert/models"
 
@@ -230,3 +234,74 @@ func TestSetEndsAt(t *testing.T) {
 		})
 	}
 }
+
+func TestGetLastEvaluationValuesForCondition(t *testing.T) {
+	genState := func(results []Evaluation) *State {
+		return &State{
+			Results: results,
+		}
+	}
+
+	t.Run("should return nil if no results", func(t *testing.T) {
+		result := genState(nil).GetLastEvaluationValuesForCondition()
+		require.Nil(t, result)
+	})
+	t.Run("should return value of the condition of the last result", func(t *testing.T) {
+		expected := rand.Float64()
+		evals := []Evaluation{
+			{
+				EvaluationTime:  time.Time{},
+				EvaluationState: 0,
+				Values: map[string]*float64{
+					"A": ptr.Float64(rand.Float64()),
+				},
+				Condition: "A",
+			},
+			{
+				EvaluationTime:  time.Time{},
+				EvaluationState: 0,
+				Values: map[string]*float64{
+					"B": ptr.Float64(rand.Float64()),
+					"A": ptr.Float64(expected),
+				},
+				Condition: "A",
+			},
+		}
+		result := genState(evals).GetLastEvaluationValuesForCondition()
+		require.Len(t, result, 1)
+		require.Contains(t, result, "A")
+		require.Equal(t, result["A"], expected)
+	})
+	t.Run("should return empty map if there is no value for condition", func(t *testing.T) {
+		evals := []Evaluation{
+			{
+				EvaluationTime:  time.Time{},
+				EvaluationState: 0,
+				Values: map[string]*float64{
+					"C": ptr.Float64(rand.Float64()),
+				},
+				Condition: "A",
+			},
+		}
+		result := genState(evals).GetLastEvaluationValuesForCondition()
+		require.NotNil(t, result)
+		require.Len(t, result, 0)
+	})
+	t.Run("should use NaN if value is not defined", func(t *testing.T) {
+		evals := []Evaluation{
+			{
+				EvaluationTime:  time.Time{},
+				EvaluationState: 0,
+				Values: map[string]*float64{
+					"A": nil,
+				},
+				Condition: "A",
+			},
+		}
+		result := genState(evals).GetLastEvaluationValuesForCondition()
+		require.NotNil(t, result)
+		require.Len(t, result, 1)
+		require.Contains(t, result, "A")
+		require.Truef(t, math.IsNaN(result["A"]), "expected NaN but got %v", result["A"])
+	})
+}