fix(core): handle precision and clean rounding of Money

scw/custom_types.go

@@ -6,6 +6,7 @@ import (
 	"fmt"
 	"io"
 	"net"
+	"strconv"
 	"strings"
 	"time"
 
@@ -76,13 +77,43 @@ type Money struct {
 	Nanos int32 `json:"nanos,omitempty"`
 }
 
-// NewMoneyFromFloat conerts a float with currency to a Money object.
-func NewMoneyFromFloat(value float64, currency string) *Money {
-	return &Money{
-		CurrencyCode: currency,
+// NewMoneyFromFloat converts a float with currency to a Money.
+//
+// value:        The float value.
+// currencyCode: The 3-letter currency code defined in ISO 4217.
+// precision:    The number of digits after the decimal point used to parse the nanos part of the value.
+//
+// Examples:
+// - (value = 1.3333, precision = 2) => Money{Units = 1, Nanos = 330000000}
+// - (value = 1.123456789, precision = 9) => Money{Units = 1, Nanos = 123456789}
+func NewMoneyFromFloat(value float64, currencyCode string, precision int) *Money {
+	if precision > 9 {
+		panic(fmt.Errorf("max precision is 9"))
+	}
+
+	strValue := strconv.FormatFloat(value, 'f', precision, 64)
+	parts := strings.Split(strValue, ".")
+
+	money := &Money{
+		CurrencyCode: currencyCode,
 		Units:        int64(value),
-		Nanos:        int32((value - float64(int64(value))) * 1000000000),
+		Nanos:        0,
+	}
+
+	// Handle nanos.
+	if len(parts) == 2 {
+		// Add leading zeros.
+		strNanos := parts[1] + "000000000"[len(parts[1]):]
+
+		n, err := strconv.ParseInt(strNanos, 10, 32)
+		if err != nil {
+			panic(fmt.Errorf("invalid nanos %s", strNanos))
+		}
+
+		money.Nanos = int32(n)
 	}
+
+	return money
 }
 
 // String returns the string representation of Money.

scw/custom_types_test.go

@@ -11,49 +11,152 @@ import (
 	"github.com/scaleway/scaleway-sdk-go/internal/testhelpers"
 )
 
+func TestMoney_NewMoneyFromFloat(t *testing.T) {
+	cases := []struct {
+		value     float64
+		currency  string
+		precision int
+		want      *Money
+	}{
+		{
+			value:     0.0,
+			currency:  "EUR",
+			precision: 0,
+			want: &Money{
+				CurrencyCode: "EUR",
+				Units:        0,
+				Nanos:        0,
+			},
+		},
+		{
+			value:     1.0,
+			currency:  "EUR",
+			precision: 3,
+			want: &Money{
+				CurrencyCode: "EUR",
+				Units:        1,
+				Nanos:        0,
+			},
+		},
+		{
+			value:     1.3,
+			currency:  "EUR",
+			precision: 3,
+			want: &Money{
+				CurrencyCode: "EUR",
+				Units:        1,
+				Nanos:        300000000,
+			},
+		},
+		{
+			value:     1.333,
+			currency:  "EUR",
+			precision: 2,
+			want: &Money{
+				CurrencyCode: "EUR",
+				Units:        1,
+				Nanos:        330000000,
+			},
+		},
+		{
+			value:     1.04,
+			currency:  "EUR",
+			precision: 1,
+			want: &Money{
+				CurrencyCode: "EUR",
+				Units:        1,
+				Nanos:        0,
+			},
+		},
+		{
+			value:     1.05,
+			currency:  "EUR",
+			precision: 1,
+			want: &Money{
+				CurrencyCode: "EUR",
+				Units:        1,
+				Nanos:        100000000,
+			},
+		},
+		{
+			value:     1.123456789,
+			currency:  "EUR",
+			precision: 9,
+			want: &Money{
+				CurrencyCode: "EUR",
+				Units:        1,
+				Nanos:        123456789,
+			},
+		},
+		{
+			value:     1.999999999,
+			currency:  "EUR",
+			precision: 9,
+			want: &Money{
+				CurrencyCode: "EUR",
+				Units:        1,
+				Nanos:        999999999,
+			},
+		},
+	}
+
+	for _, c := range cases {
+		t.Run(c.want.String(), func(t *testing.T) {
+			testhelpers.Equals(t, c.want, NewMoneyFromFloat(c.value, c.currency, c.precision))
+		})
+	}
+}
+
 func TestMoney_String(t *testing.T) {
 	cases := []struct {
-		money Money
+		money *Money
 		want  string
 	}{
 		{
-			money: Money{
+			money: &Money{
 				CurrencyCode: "EUR",
 				Units:        10,
 			},
 			want: "€ 10.00",
 		},
 		{
-			money: Money{
+			money: &Money{
 				CurrencyCode: "USD",
 				Units:        10,
 				Nanos:        1,
 			},
 			want: "$ 10.000000001",
 		},
 		{
-			money: Money{
+			money: &Money{
 				CurrencyCode: "EUR",
 				Nanos:        100000000,
 			},
 			want: "€ 0.10",
 		},
 		{
-			money: Money{
+			money: &Money{
 				CurrencyCode: "EUR",
 				Nanos:        500000,
 			},
 			want: "€ 0.0005",
 		},
 		{
-			money: Money{
+			money: &Money{
+				CurrencyCode: "EUR",
+				Nanos:        333000000,
+			},
+			want: "€ 0.333",
+		},
+		{
+			money: &Money{
 				CurrencyCode: "EUR",
 				Nanos:        123456789,
 			},
 			want: "€ 0.123456789",
 		},
 		{
-			money: Money{
+			money: &Money{
 				CurrencyCode: "?",
 			},
 			want: "? 0.00",