From b6a71563008f92db7ffb2457172aa7d011ae5033 Mon Sep 17 00:00:00 2001
From: Kyle Brandt <kyle@grafana.com>
Date: Wed, 21 Jul 2021 10:04:40 -0400
Subject: [PATCH] Alerting: Handle marshaling Inf values (#36947)

* SSE: change EvalMatch json value encoding to string
* update MarshalJSON on null.Float to handle inf as null
fixes #36424
---
 pkg/components/null/float.go |  4 ++--
 pkg/expr/classic/classic.go  | 18 ++++++++++++++++++
 2 files changed, 20 insertions(+), 2 deletions(-)

diff --git a/pkg/components/null/float.go b/pkg/components/null/float.go
index 8dd87f03f13..64bcf43781f 100644
--- a/pkg/components/null/float.go
+++ b/pkg/components/null/float.go
@@ -98,9 +98,9 @@ func (f *Float) UnmarshalText(text []byte) error {
 }
 
 // MarshalJSON implements json.Marshaler.
-// It will encode null if this Float is null.
+// It will encode null if this Float is null, NaN, of Inf.
 func (f Float) MarshalJSON() ([]byte, error) {
-	if !f.Valid || math.IsNaN(f.Float64) {
+	if !f.Valid || math.IsNaN(f.Float64) || math.IsInf(f.Float64, 0) {
 		return []byte(nullString), nil
 	}
 	return []byte(strconv.FormatFloat(f.Float64, 'f', -1, 64)), nil
diff --git a/pkg/expr/classic/classic.go b/pkg/expr/classic/classic.go
index 66b22d9014b..830d1ba1f1c 100644
--- a/pkg/expr/classic/classic.go
+++ b/pkg/expr/classic/classic.go
@@ -4,6 +4,7 @@ import (
 	"context"
 	"encoding/json"
 	"fmt"
+	"strconv"
 
 	"github.com/grafana/grafana-plugin-sdk-go/data"
 	"github.com/grafana/grafana/pkg/expr/mathexp"
@@ -61,12 +62,29 @@ func (ccc *ConditionsCmd) NeedsVars() []string {
 }
 
 // EvalMatch represents the series violating the threshold.
+// It goes into the metadata of data frames so it can be extracted.
 type EvalMatch struct {
 	Value  *float64    `json:"value"`
 	Metric string      `json:"metric"`
 	Labels data.Labels `json:"labels"`
 }
 
+func (em EvalMatch) MarshalJSON() ([]byte, error) {
+	fs := ""
+	if em.Value != nil {
+		fs = strconv.FormatFloat(*em.Value, 'f', -1, 64)
+	}
+	return json.Marshal(struct {
+		Value  string      `json:"value"`
+		Metric string      `json:"metric"`
+		Labels data.Labels `json:"labels"`
+	}{
+		fs,
+		em.Metric,
+		em.Labels,
+	})
+}
+
 // Execute runs the command and returns the results or an error if the command
 // failed to execute.
 func (ccc *ConditionsCmd) Execute(ctx context.Context, vars mathexp.Vars) (mathexp.Results, error) {