fix: prevent formating issues with decimal

Author: dunglas

decimal.go

@@ -5,6 +5,7 @@ import (
 	"io"
 	"math"
 	"strconv"
+	"strings"
 )
 
 const maxDecDigit = 3
@@ -21,18 +22,18 @@ func marshalDecimal(b io.StringWriter, d float64) error {
 	const TH = 0.001
 
 	rounded := math.RoundToEven(d/TH) * TH
-	i, frac := math.Modf(math.RoundToEven(d/TH) * TH)
+	i, frac := math.Modf(rounded)
 
 	if i < -999999999999 || i > 999999999999 {
 		return ErrInvalidDecimal
 	}
 
-	if _, err := b.WriteString(strconv.FormatFloat(rounded, 'f', -1, 64)); err != nil {
+	if _, err := b.WriteString(strings.TrimRight(strconv.FormatFloat(rounded, 'f', 3, 64), "0")); err != nil {
 		return err
 	}
 
 	if frac == 0 {
-		_, err := b.WriteString(".0")
+		_, err := b.WriteString("0")
 
 		return err
 	}

decimal_test.go

@@ -23,6 +23,7 @@ func TestDecimalMarshalSFV(t *testing.T) {
 		{9999999999999, "", false},
 		{-9999999999999.0, "", false},
 		{9999999999999.0, "", false},
+		{1.9, "1.9", true},
 	}
 
 	var b strings.Builder

list_test.go

@@ -120,21 +120,31 @@ func FuzzUnmarshalList(f *testing.F) {
 		`("é")`,
 		`(""`,
 		`(`,
+		"1.9",
 	}
 
 	for _, t := range testCases {
 		f.Add(t)
 	}
 
 	f.Fuzz(func(t *testing.T, b string) {
-		l, err := UnmarshalList([]string{b})
-
+		unmarshaled, err := UnmarshalList([]string{b})
 		if err != nil {
 			return
 		}
 
-		if _, err := Marshal(l); err != nil {
-			t.Errorf("Unexpected marshaling error %q for %q, %#v", err, b, l)
+		reMarshaled, err := Marshal(unmarshaled)
+		if err != nil {
+			t.Errorf("Unexpected marshaling error %q for %q, %#v", err, b, unmarshaled)
+		}
+
+		reUnmarshaled, err := UnmarshalList([]string{reMarshaled})
+		if err != nil {
+			t.Errorf("Unexpected remarshaling error %q for %q; original %q", err, reMarshaled, b)
+		}
+
+		if !reflect.DeepEqual(unmarshaled, reUnmarshaled) {
+			t.Errorf("Unmarshaled and re-unmarshaled doesn't match: %#v; %#v", unmarshaled, reUnmarshaled)
 		}
 	})
 }