feat(num): support custom formatting

.golangci.yml

@@ -32,6 +32,7 @@ linters-settings:
       - commentedOutCode
       - appendAssign
       - unnecessaryBlock
+      - redundantSprint
 
 linters:
   disable-all: true

num.go

@@ -2,6 +2,8 @@ package jx
 
 import (
 	"bytes"
+	"fmt"
+	"math/big"
 
 	"github.com/go-faster/errors"
 )
@@ -114,6 +116,30 @@ func (n Num) String() string {
 	return string(n)
 }
 
+// Format implements fmt.Formatter.
+func (n Num) Format(f fmt.State, verb rune) {
+	switch verb {
+	case 's', 'v':
+		_, _ = f.Write(n)
+	case 'd':
+		d, err := n.Int64()
+		if err != nil {
+			fmt.Fprintf(f, "%%!invalid(Num=%s)", n.String())
+			return
+		}
+		v := big.NewInt(d)
+		v.Format(f, verb)
+	case 'f':
+		d, err := n.Float64()
+		if err != nil {
+			fmt.Fprintf(f, "%%!invalid(Num=%s)", n.String())
+			return
+		}
+		v := big.NewFloat(d)
+		v.Format(f, verb)
+	}
+}
+
 // Sign reports sign of number.
 //
 // 0 is zero, 1 is positive, -1 is negative.

num_test.go

@@ -1,6 +1,7 @@
 package jx
 
 import (
+	"fmt"
 	"testing"
 
 	"github.com/stretchr/testify/assert"
@@ -21,6 +22,15 @@ func TestEncoder_Num(t *testing.T) {
 }
 
 func TestNum(t *testing.T) {
+	t.Run("Format", func(t *testing.T) {
+		assert.Equal(t, `-12`, fmt.Sprintf("%d", Num(`"-12.0"`)))
+		assert.Equal(t, `-12.000000`, fmt.Sprintf("%f", Num(`"-12.0"`)))
+		assert.Equal(t, `%!invalid(Num=f)`, fmt.Sprintf("%f", Num(`f`)))
+		assert.Equal(t, `"-12.0"`, fmt.Sprintf("%s", Num(`"-12.0"`)))
+		assert.Equal(t, `"-12.0"`, fmt.Sprintf("%v", Num(`"-12.0"`)))
+		assert.Equal(t, `%!invalid(Num=f)`, fmt.Sprintf("%d", Num(`f`)))
+		assert.Equal(t, `%!invalid(Num="-12.1")`, fmt.Sprintf("%d", Num(`"-12.1"`)))
+	})
 	t.Run("String", func(t *testing.T) {
 		for _, cc := range []struct {
 			Name   string