From 31b2360af5d02800c548b502403408794cd38b9a Mon Sep 17 00:00:00 2001
From: dmitrybarsukov <dmitrybarsukov96@gmail.com>
Date: Sun, 25 May 2025 22:54:08 +0200
Subject: [PATCH] Return error if trying to marshal +Inf, -Inf or NaN

---
 jwriter/writer.go    | 27 +++++++++++++++++++++++++++
 tests/errors.go      |  6 ++++++
 tests/errors_test.go | 38 ++++++++++++++++++++++++++++++++++++++
 3 files changed, 71 insertions(+)

diff --git a/jwriter/writer.go b/jwriter/writer.go
index 34b0ade..6f1403a 100644
--- a/jwriter/writer.go
+++ b/jwriter/writer.go
@@ -2,7 +2,9 @@
 package jwriter
 
 import (
+	"fmt"
 	"io"
+	"math"
 	"strconv"
 	"unicode/utf8"
 
@@ -248,11 +250,19 @@ func (w *Writer) Int64Str(n int64) {
 }
 
 func (w *Writer) Float32(n float32) {
+	if w.checkIsUnsupportedFloat(float64(n)) {
+		return
+	}
+
 	w.Buffer.EnsureSpace(20)
 	w.Buffer.Buf = strconv.AppendFloat(w.Buffer.Buf, float64(n), 'g', -1, 32)
 }
 
 func (w *Writer) Float32Str(n float32) {
+	if w.checkIsUnsupportedFloat(float64(n)) {
+		return
+	}
+
 	w.Buffer.EnsureSpace(20)
 	w.Buffer.Buf = append(w.Buffer.Buf, '"')
 	w.Buffer.Buf = strconv.AppendFloat(w.Buffer.Buf, float64(n), 'g', -1, 32)
@@ -260,11 +270,19 @@ func (w *Writer) Float32Str(n float32) {
 }
 
 func (w *Writer) Float64(n float64) {
+	if w.checkIsUnsupportedFloat(n) {
+		return
+	}
+
 	w.Buffer.EnsureSpace(20)
 	w.Buffer.Buf = strconv.AppendFloat(w.Buffer.Buf, n, 'g', -1, 64)
 }
 
 func (w *Writer) Float64Str(n float64) {
+	if w.checkIsUnsupportedFloat(n) {
+		return
+	}
+
 	w.Buffer.EnsureSpace(20)
 	w.Buffer.Buf = append(w.Buffer.Buf, '"')
 	w.Buffer.Buf = strconv.AppendFloat(w.Buffer.Buf, float64(n), 'g', -1, 64)
@@ -415,3 +433,12 @@ func (w *Writer) base64(in []byte) {
 		w.Buffer.Buf = append(w.Buffer.Buf, byte(padChar), byte(padChar))
 	}
 }
+
+func (w *Writer) checkIsUnsupportedFloat(val float64) bool {
+	isUnsupported := math.IsNaN(val) || math.IsInf(val, 0)
+	if isUnsupported && w.Error == nil {
+		w.Error = fmt.Errorf("json: unsupported value: %v", val)
+	}
+
+	return isUnsupported
+}
diff --git a/tests/errors.go b/tests/errors.go
index 14360fc..2a545d1 100644
--- a/tests/errors.go
+++ b/tests/errors.go
@@ -24,3 +24,9 @@ type ErrorNestedStruct struct {
 
 //easyjson:json
 type ErrorIntMap map[uint32]string
+
+//easyjson:json
+type ErrorFloatTypes struct {
+	Float64 float64 `json:"float64"`
+	Float32 float32 `json:"float32"`
+}
diff --git a/tests/errors_test.go b/tests/errors_test.go
index 40fa335..756ef11 100644
--- a/tests/errors_test.go
+++ b/tests/errors_test.go
@@ -1,6 +1,7 @@
 package tests
 
 import (
+	"math"
 	"testing"
 
 	"github.com/mailru/easyjson/jlexer"
@@ -283,3 +284,40 @@ func TestMultipleErrorsIntMap(t *testing.T) {
 		}
 	}
 }
+
+func TestUnsupportedFloatValues(t *testing.T) {
+	for i, test := range []struct {
+		Value       ErrorFloatTypes
+		ExpectedErr string
+	}{
+		{
+			Value:       ErrorFloatTypes{Float64: math.NaN()},
+			ExpectedErr: "json: unsupported value: NaN",
+		},
+		{
+			Value:       ErrorFloatTypes{Float64: math.Inf(1)},
+			ExpectedErr: "json: unsupported value: +Inf",
+		},
+		{
+			Value:       ErrorFloatTypes{Float64: math.Inf(-1)},
+			ExpectedErr: "json: unsupported value: -Inf",
+		},
+		{
+			Value:       ErrorFloatTypes{Float32: float32(math.NaN())},
+			ExpectedErr: "json: unsupported value: NaN",
+		},
+		{
+			Value:       ErrorFloatTypes{Float32: float32(math.Inf(1))},
+			ExpectedErr: "json: unsupported value: +Inf",
+		},
+		{
+			Value:       ErrorFloatTypes{Float32: float32(math.Inf(-1))},
+			ExpectedErr: "json: unsupported value: -Inf",
+		},
+	} {
+		_, err := test.Value.MarshalJSON()
+		if err == nil || err.Error() != test.ExpectedErr {
+			t.Errorf("[%d] TestUnsupportedFloatValues(): error: want %s, got %v", i, test.ExpectedErr, err)
+		}
+	}
+}