From ab9046a9ad7bd37d05c4bbe6a66d06c351e4e1b2 Mon Sep 17 00:00:00 2001
From: hunjixin <1084400399@qq.com>
Date: Thu, 19 Oct 2023 23:50:41 +0800
Subject: [PATCH] feat: unmarshal empty string as zero

---
 decimal.go      | 225 +++++++++++++++++++++++-------------------------
 decimal_test.go |  15 ++++
 2 files changed, 122 insertions(+), 118 deletions(-)

diff --git a/decimal.go b/decimal.go
index c614ea79..4f9df0e7 100644
--- a/decimal.go
+++ b/decimal.go
@@ -4,14 +4,14 @@
 //
 // The best way to create a new Decimal is to use decimal.NewFromString, ex:
 //
-//     n, err := decimal.NewFromString("-123.4567")
-//     n.String() // output: "-123.4567"
+//	n, err := decimal.NewFromString("-123.4567")
+//	n.String() // output: "-123.4567"
 //
 // To use Decimal as part of a struct:
 //
-//     type Struct struct {
-//         Number Decimal
-//     }
+//	type Struct struct {
+//	    Number Decimal
+//	}
 //
 // Note: This can "only" represent numbers with a maximum of 2^31 digits after the decimal point.
 package decimal
@@ -32,16 +32,15 @@ import (
 //
 // Example:
 //
-//     d1 := decimal.NewFromFloat(2).Div(decimal.NewFromFloat(3))
-//     d1.String() // output: "0.6666666666666667"
-//     d2 := decimal.NewFromFloat(2).Div(decimal.NewFromFloat(30000))
-//     d2.String() // output: "0.0000666666666667"
-//     d3 := decimal.NewFromFloat(20000).Div(decimal.NewFromFloat(3))
-//     d3.String() // output: "6666.6666666666666667"
-//     decimal.DivisionPrecision = 3
-//     d4 := decimal.NewFromFloat(2).Div(decimal.NewFromFloat(3))
-//     d4.String() // output: "0.667"
-//
+//	d1 := decimal.NewFromFloat(2).Div(decimal.NewFromFloat(3))
+//	d1.String() // output: "0.6666666666666667"
+//	d2 := decimal.NewFromFloat(2).Div(decimal.NewFromFloat(30000))
+//	d2.String() // output: "0.0000666666666667"
+//	d3 := decimal.NewFromFloat(20000).Div(decimal.NewFromFloat(3))
+//	d3.String() // output: "6666.6666666666666667"
+//	decimal.DivisionPrecision = 3
+//	d4 := decimal.NewFromFloat(2).Div(decimal.NewFromFloat(3))
+//	d4.String() // output: "0.667"
 var DivisionPrecision = 16
 
 // MarshalJSONWithoutQuotes should be set to true if you want the decimal to
@@ -95,8 +94,8 @@ func New(value int64, exp int32) Decimal {
 //
 // Example:
 //
-//     NewFromInt(123).String() // output: "123"
-//     NewFromInt(-10).String() // output: "-10"
+//	NewFromInt(123).String() // output: "123"
+//	NewFromInt(-10).String() // output: "-10"
 func NewFromInt(value int64) Decimal {
 	return Decimal{
 		value: big.NewInt(value),
@@ -108,8 +107,8 @@ func NewFromInt(value int64) Decimal {
 //
 // Example:
 //
-//     NewFromInt(123).String() // output: "123"
-//     NewFromInt(-10).String() // output: "-10"
+//	NewFromInt(123).String() // output: "123"
+//	NewFromInt(-10).String() // output: "-10"
 func NewFromInt32(value int32) Decimal {
 	return Decimal{
 		value: big.NewInt(int64(value)),
@@ -130,10 +129,9 @@ func NewFromBigInt(value *big.Int, exp int32) Decimal {
 //
 // Example:
 //
-//     d, err := NewFromString("-123.45")
-//     d2, err := NewFromString(".0001")
-//     d3, err := NewFromString("1.47000")
-//
+//	d, err := NewFromString("-123.45")
+//	d2, err := NewFromString(".0001")
+//	d3, err := NewFromString("1.47000")
 func NewFromString(value string) (Decimal, error) {
 	originalInput := value
 	var intString string
@@ -211,15 +209,14 @@ func NewFromString(value string) (Decimal, error) {
 //
 // Example:
 //
-//     r := regexp.MustCompile("[$,]")
-//     d1, err := NewFromFormattedString("$5,125.99", r)
+//	r := regexp.MustCompile("[$,]")
+//	d1, err := NewFromFormattedString("$5,125.99", r)
 //
-//     r2 := regexp.MustCompile("[_]")
-//     d2, err := NewFromFormattedString("1_000_000", r2)
-//
-//     r3 := regexp.MustCompile("[USD\\s]")
-//     d3, err := NewFromFormattedString("5000 USD", r3)
+//	r2 := regexp.MustCompile("[_]")
+//	d2, err := NewFromFormattedString("1_000_000", r2)
 //
+//	r3 := regexp.MustCompile("[USD\\s]")
+//	d3, err := NewFromFormattedString("5000 USD", r3)
 func NewFromFormattedString(value string, replRegexp *regexp.Regexp) (Decimal, error) {
 	parsedValue := replRegexp.ReplaceAllString(value, "")
 	d, err := NewFromString(parsedValue)
@@ -234,9 +231,8 @@ func NewFromFormattedString(value string, replRegexp *regexp.Regexp) (Decimal, e
 //
 // Example:
 //
-//     d := RequireFromString("-123.45")
-//     d2 := RequireFromString(".0001")
-//
+//	d := RequireFromString("-123.45")
+//	d2 := RequireFromString(".0001")
 func RequireFromString(value string) Decimal {
 	dec, err := NewFromString(value)
 	if err != nil {
@@ -332,8 +328,7 @@ func newFromFloat(val float64, bits uint64, flt *floatInfo) Decimal {
 //
 // Example:
 //
-//     NewFromFloatWithExponent(123.456, -2).String() // output: "123.46"
-//
+//	NewFromFloatWithExponent(123.456, -2).String() // output: "123.46"
 func NewFromFloatWithExponent(value float64, exp int32) Decimal {
 	if math.IsNaN(value) || math.IsInf(value, 0) {
 		panic(fmt.Sprintf("Cannot create a Decimal from %v", value))
@@ -430,7 +425,7 @@ func (d Decimal) Copy() Decimal {
 //
 // Example:
 //
-// 	d := New(12345, -4)
+//	d := New(12345, -4)
 //	d2 := d.rescale(-1)
 //	d3 := d2.rescale(-4)
 //	println(d1)
@@ -442,7 +437,6 @@ func (d Decimal) Copy() Decimal {
 //	1.2345
 //	1.2
 //	1.2000
-//
 func (d Decimal) rescale(exp int32) Decimal {
 	d.ensureInitialized()
 
@@ -554,9 +548,11 @@ func (d Decimal) Div(d2 Decimal) Decimal {
 
 // QuoRem does division with remainder
 // d.QuoRem(d2,precision) returns quotient q and remainder r such that
-//   d = d2 * q + r, q an integer multiple of 10^(-precision)
-//   0 <= r < abs(d2) * 10 ^(-precision) if d>=0
-//   0 >= r > -abs(d2) * 10 ^(-precision) if d<0
+//
+//	d = d2 * q + r, q an integer multiple of 10^(-precision)
+//	0 <= r < abs(d2) * 10 ^(-precision) if d>=0
+//	0 >= r > -abs(d2) * 10 ^(-precision) if d<0
+//
 // Note that precision<0 is allowed as input.
 func (d Decimal) QuoRem(d2 Decimal, precision int32) (Decimal, Decimal) {
 	d.ensureInitialized()
@@ -599,8 +595,10 @@ func (d Decimal) QuoRem(d2 Decimal, precision int32) (Decimal, Decimal) {
 
 // DivRound divides and rounds to a given precision
 // i.e. to an integer multiple of 10^(-precision)
-//   for a positive quotient digit 5 is rounded up, away from 0
-//   if the quotient is negative then digit 5 is rounded down, away from 0
+//
+//	for a positive quotient digit 5 is rounded up, away from 0
+//	if the quotient is negative then digit 5 is rounded down, away from 0
+//
 // Note that precision<0 is allowed as input.
 func (d Decimal) DivRound(d2 Decimal, precision int32) Decimal {
 	// QuoRem already checks initialization
@@ -655,9 +653,8 @@ func (d Decimal) Pow(d2 Decimal) Decimal {
 //
 // Example:
 //
-//     NewFromFloat(26.1).ExpHullAbrham(2).String()    // output: "220000000000"
-//     NewFromFloat(26.1).ExpHullAbrham(20).String()   // output: "216314672147.05767284"
-//
+//	NewFromFloat(26.1).ExpHullAbrham(2).String()    // output: "220000000000"
+//	NewFromFloat(26.1).ExpHullAbrham(20).String()   // output: "216314672147.05767284"
 func (d Decimal) ExpHullAbrham(overallPrecision uint32) (Decimal, error) {
 	// Algorithm based on Variable precision exponential function.
 	// ACM Transactions on Mathematical Software by T. E. Hull & A. Abrham.
@@ -747,15 +744,14 @@ func (d Decimal) ExpHullAbrham(overallPrecision uint32) (Decimal, error) {
 //
 // Example:
 //
-//     d, err := NewFromFloat(26.1).ExpTaylor(2).String()
-//     d.String()  // output: "216314672147.06"
-//
-//     NewFromFloat(26.1).ExpTaylor(20).String()
-//     d.String()  // output: "216314672147.05767284062928674083"
+//	d, err := NewFromFloat(26.1).ExpTaylor(2).String()
+//	d.String()  // output: "216314672147.06"
 //
-//     NewFromFloat(26.1).ExpTaylor(-10).String()
-//     d.String()  // output: "220000000000"
+//	NewFromFloat(26.1).ExpTaylor(20).String()
+//	d.String()  // output: "216314672147.05767284062928674083"
 //
+//	NewFromFloat(26.1).ExpTaylor(-10).String()
+//	d.String()  // output: "220000000000"
 func (d Decimal) ExpTaylor(precision int32) (Decimal, error) {
 	// Note(mwoss): Implementation can be optimized by exclusively using big.Int API only
 	if d.IsZero() {
@@ -851,10 +847,9 @@ func abs(n int32) int32 {
 
 // Cmp compares the numbers represented by d and d2 and returns:
 //
-//     -1 if d <  d2
-//      0 if d == d2
-//     +1 if d >  d2
-//
+//	-1 if d <  d2
+//	 0 if d == d2
+//	+1 if d >  d2
 func (d Decimal) Cmp(d2 Decimal) int {
 	d.ensureInitialized()
 	d2.ensureInitialized()
@@ -905,7 +900,6 @@ func (d Decimal) LessThanOrEqual(d2 Decimal) bool {
 //	-1 if d <  0
 //	 0 if d == 0
 //	+1 if d >  0
-//
 func (d Decimal) Sign() int {
 	if d.value == nil {
 		return 0
@@ -1014,13 +1008,12 @@ func (d Decimal) InexactFloat64() float64 {
 //
 // Example:
 //
-//     d := New(-12345, -3)
-//     println(d.String())
+//	d := New(-12345, -3)
+//	println(d.String())
 //
 // Output:
 //
-//     -12.345
-//
+//	-12.345
 func (d Decimal) String() string {
 	return d.string(true)
 }
@@ -1030,14 +1023,13 @@ func (d Decimal) String() string {
 //
 // Example:
 //
-// 	   NewFromFloat(0).StringFixed(2) // output: "0.00"
-// 	   NewFromFloat(0).StringFixed(0) // output: "0"
-// 	   NewFromFloat(5.45).StringFixed(0) // output: "5"
-// 	   NewFromFloat(5.45).StringFixed(1) // output: "5.5"
-// 	   NewFromFloat(5.45).StringFixed(2) // output: "5.45"
-// 	   NewFromFloat(5.45).StringFixed(3) // output: "5.450"
-// 	   NewFromFloat(545).StringFixed(-1) // output: "550"
-//
+//	NewFromFloat(0).StringFixed(2) // output: "0.00"
+//	NewFromFloat(0).StringFixed(0) // output: "0"
+//	NewFromFloat(5.45).StringFixed(0) // output: "5"
+//	NewFromFloat(5.45).StringFixed(1) // output: "5.5"
+//	NewFromFloat(5.45).StringFixed(2) // output: "5.45"
+//	NewFromFloat(5.45).StringFixed(3) // output: "5.450"
+//	NewFromFloat(545).StringFixed(-1) // output: "550"
 func (d Decimal) StringFixed(places int32) string {
 	rounded := d.Round(places)
 	return rounded.string(false)
@@ -1048,14 +1040,13 @@ func (d Decimal) StringFixed(places int32) string {
 //
 // Example:
 //
-// 	   NewFromFloat(0).StringFixedBank(2) // output: "0.00"
-// 	   NewFromFloat(0).StringFixedBank(0) // output: "0"
-// 	   NewFromFloat(5.45).StringFixedBank(0) // output: "5"
-// 	   NewFromFloat(5.45).StringFixedBank(1) // output: "5.4"
-// 	   NewFromFloat(5.45).StringFixedBank(2) // output: "5.45"
-// 	   NewFromFloat(5.45).StringFixedBank(3) // output: "5.450"
-// 	   NewFromFloat(545).StringFixedBank(-1) // output: "540"
-//
+//	NewFromFloat(0).StringFixedBank(2) // output: "0.00"
+//	NewFromFloat(0).StringFixedBank(0) // output: "0"
+//	NewFromFloat(5.45).StringFixedBank(0) // output: "5"
+//	NewFromFloat(5.45).StringFixedBank(1) // output: "5.4"
+//	NewFromFloat(5.45).StringFixedBank(2) // output: "5.45"
+//	NewFromFloat(5.45).StringFixedBank(3) // output: "5.450"
+//	NewFromFloat(545).StringFixedBank(-1) // output: "540"
 func (d Decimal) StringFixedBank(places int32) string {
 	rounded := d.RoundBank(places)
 	return rounded.string(false)
@@ -1073,9 +1064,8 @@ func (d Decimal) StringFixedCash(interval uint8) string {
 //
 // Example:
 //
-// 	   NewFromFloat(5.45).Round(1).String() // output: "5.5"
-// 	   NewFromFloat(545).Round(-1).String() // output: "550"
-//
+//	NewFromFloat(5.45).Round(1).String() // output: "5.5"
+//	NewFromFloat(545).Round(-1).String() // output: "550"
 func (d Decimal) Round(places int32) Decimal {
 	if d.exp == -places {
 		return d
@@ -1104,11 +1094,10 @@ func (d Decimal) Round(places int32) Decimal {
 //
 // Example:
 //
-//     NewFromFloat(545).RoundCeil(-2).String()   // output: "600"
-//     NewFromFloat(500).RoundCeil(-2).String()   // output: "500"
-//     NewFromFloat(1.1001).RoundCeil(2).String() // output: "1.11"
-//     NewFromFloat(-1.454).RoundCeil(1).String() // output: "-1.5"
-//
+//	NewFromFloat(545).RoundCeil(-2).String()   // output: "600"
+//	NewFromFloat(500).RoundCeil(-2).String()   // output: "500"
+//	NewFromFloat(1.1001).RoundCeil(2).String() // output: "1.11"
+//	NewFromFloat(-1.454).RoundCeil(1).String() // output: "-1.5"
 func (d Decimal) RoundCeil(places int32) Decimal {
 	if d.exp >= -places {
 		return d
@@ -1130,11 +1119,10 @@ func (d Decimal) RoundCeil(places int32) Decimal {
 //
 // Example:
 //
-//     NewFromFloat(545).RoundFloor(-2).String()   // output: "500"
-//     NewFromFloat(-500).RoundFloor(-2).String()   // output: "-500"
-//     NewFromFloat(1.1001).RoundFloor(2).String() // output: "1.1"
-//     NewFromFloat(-1.454).RoundFloor(1).String() // output: "-1.4"
-//
+//	NewFromFloat(545).RoundFloor(-2).String()   // output: "500"
+//	NewFromFloat(-500).RoundFloor(-2).String()   // output: "-500"
+//	NewFromFloat(1.1001).RoundFloor(2).String() // output: "1.1"
+//	NewFromFloat(-1.454).RoundFloor(1).String() // output: "-1.4"
 func (d Decimal) RoundFloor(places int32) Decimal {
 	if d.exp >= -places {
 		return d
@@ -1156,11 +1144,10 @@ func (d Decimal) RoundFloor(places int32) Decimal {
 //
 // Example:
 //
-//     NewFromFloat(545).RoundUp(-2).String()   // output: "600"
-//     NewFromFloat(500).RoundUp(-2).String()   // output: "500"
-//     NewFromFloat(1.1001).RoundUp(2).String() // output: "1.11"
-//     NewFromFloat(-1.454).RoundUp(1).String() // output: "-1.4"
-//
+//	NewFromFloat(545).RoundUp(-2).String()   // output: "600"
+//	NewFromFloat(500).RoundUp(-2).String()   // output: "500"
+//	NewFromFloat(1.1001).RoundUp(2).String() // output: "1.11"
+//	NewFromFloat(-1.454).RoundUp(1).String() // output: "-1.4"
 func (d Decimal) RoundUp(places int32) Decimal {
 	if d.exp >= -places {
 		return d
@@ -1184,11 +1171,10 @@ func (d Decimal) RoundUp(places int32) Decimal {
 //
 // Example:
 //
-//     NewFromFloat(545).RoundDown(-2).String()   // output: "500"
-//     NewFromFloat(-500).RoundDown(-2).String()   // output: "-500"
-//     NewFromFloat(1.1001).RoundDown(2).String() // output: "1.1"
-//     NewFromFloat(-1.454).RoundDown(1).String() // output: "-1.5"
-//
+//	NewFromFloat(545).RoundDown(-2).String()   // output: "500"
+//	NewFromFloat(-500).RoundDown(-2).String()   // output: "-500"
+//	NewFromFloat(1.1001).RoundDown(2).String() // output: "1.1"
+//	NewFromFloat(-1.454).RoundDown(1).String() // output: "-1.5"
 func (d Decimal) RoundDown(places int32) Decimal {
 	if d.exp >= -places {
 		return d
@@ -1209,13 +1195,12 @@ func (d Decimal) RoundDown(places int32) Decimal {
 //
 // Examples:
 //
-// 	   NewFromFloat(5.45).RoundBank(1).String() // output: "5.4"
-// 	   NewFromFloat(545).RoundBank(-1).String() // output: "540"
-// 	   NewFromFloat(5.46).RoundBank(1).String() // output: "5.5"
-// 	   NewFromFloat(546).RoundBank(-1).String() // output: "550"
-// 	   NewFromFloat(5.55).RoundBank(1).String() // output: "5.6"
-// 	   NewFromFloat(555).RoundBank(-1).String() // output: "560"
-//
+//	NewFromFloat(5.45).RoundBank(1).String() // output: "5.4"
+//	NewFromFloat(545).RoundBank(-1).String() // output: "540"
+//	NewFromFloat(5.46).RoundBank(1).String() // output: "5.5"
+//	NewFromFloat(546).RoundBank(-1).String() // output: "550"
+//	NewFromFloat(5.55).RoundBank(1).String() // output: "5.6"
+//	NewFromFloat(555).RoundBank(-1).String() // output: "560"
 func (d Decimal) RoundBank(places int32) Decimal {
 
 	round := d.Round(places)
@@ -1237,11 +1222,13 @@ func (d Decimal) RoundBank(places int32) Decimal {
 // interval. The amount payable for a cash transaction is rounded to the nearest
 // multiple of the minimum currency unit available. The following intervals are
 // available: 5, 10, 25, 50 and 100; any other number throws a panic.
-//	    5:   5 cent rounding 3.43 => 3.45
-// 	   10:  10 cent rounding 3.45 => 3.50 (5 gets rounded up)
-// 	   25:  25 cent rounding 3.41 => 3.50
-// 	   50:  50 cent rounding 3.75 => 4.00
-// 	  100: 100 cent rounding 3.50 => 4.00
+//
+//	  5:   5 cent rounding 3.43 => 3.45
+//	 10:  10 cent rounding 3.45 => 3.50 (5 gets rounded up)
+//	 25:  25 cent rounding 3.41 => 3.50
+//	 50:  50 cent rounding 3.75 => 4.00
+//	100: 100 cent rounding 3.50 => 4.00
+//
 // For more details: https://en.wikipedia.org/wiki/Cash_rounding
 func (d Decimal) RoundCash(interval uint8) Decimal {
 	var iVal *big.Int
@@ -1310,8 +1297,7 @@ func (d Decimal) Ceil() Decimal {
 //
 // Example:
 //
-//     decimal.NewFromString("123.456").Truncate(2).String() // "123.45"
-//
+//	decimal.NewFromString("123.456").Truncate(2).String() // "123.45"
 func (d Decimal) Truncate(precision int32) Decimal {
 	d.ensureInitialized()
 	if precision >= 0 && -precision > d.exp {
@@ -1330,7 +1316,10 @@ func (d *Decimal) UnmarshalJSON(decimalBytes []byte) error {
 	if err != nil {
 		return fmt.Errorf("error decoding string '%s': %s", decimalBytes, err)
 	}
-
+	if len(str) == 0 {
+		*d = Zero
+		return nil
+	}
 	decimal, err := NewFromString(str)
 	*d = decimal
 	if err != nil {
@@ -1515,7 +1504,7 @@ func (d *Decimal) ensureInitialized() {
 //
 // To call this function with an array, you must do:
 //
-//     Min(arr[0], arr[1:]...)
+//	Min(arr[0], arr[1:]...)
 //
 // This makes it harder to accidentally call Min with 0 arguments.
 func Min(first Decimal, rest ...Decimal) Decimal {
@@ -1532,7 +1521,7 @@ func Min(first Decimal, rest ...Decimal) Decimal {
 //
 // To call this function with an array, you must do:
 //
-//     Max(arr[0], arr[1:]...)
+//	Max(arr[0], arr[1:]...)
 //
 // This makes it harder to accidentally call Max with 0 arguments.
 func Max(first Decimal, rest ...Decimal) Decimal {
@@ -1599,7 +1588,7 @@ func unquoteIfQuoted(value interface{}) (string, error) {
 	}
 
 	// If the amount is quoted, strip the quotes
-	if len(bytes) > 2 && bytes[0] == '"' && bytes[len(bytes)-1] == '"' {
+	if len(bytes) >= 2 && bytes[0] == '"' && bytes[len(bytes)-1] == '"' {
 		bytes = bytes[1 : len(bytes)-1]
 	}
 	return string(bytes), nil
diff --git a/decimal_test.go b/decimal_test.go
index 2b3a99e1..061a4290 100644
--- a/decimal_test.go
+++ b/decimal_test.go
@@ -623,6 +623,21 @@ func TestUnmarshalJSONNull(t *testing.T) {
 	}
 }
 
+func TestUnmarshalJSONEmptyString(t *testing.T) {
+	var doc struct {
+		Amount Decimal `json:"amount"`
+	}
+	docStr := `{"amount": ""}`
+	err := json.Unmarshal([]byte(docStr), &doc)
+	if err != nil {
+		t.Errorf("error unmarshaling %s: %v", docStr, err)
+	} else if !doc.Amount.Equal(Zero) {
+		t.Errorf("expected Zero, got %s (%s, %d)",
+			doc.Amount.String(),
+			doc.Amount.value.String(), doc.Amount.exp)
+	}
+}
+
 func TestBadJSON(t *testing.T) {
 	for _, testCase := range []string{
 		"]o_o[",