feat: support env tag in config (#2577)

* feat: support env tag in config

* chore: add more tests

* chore: add more tests, add stringx.Join

* fix: test fail

* chore: remove print code

* chore: rename variable

core/lang/lang.go

@@ -1,5 +1,11 @@
 package lang
 
+import (
+	"fmt"
+	"reflect"
+	"strconv"
+)
+
 // Placeholder is a placeholder object that can be used globally.
 var Placeholder PlaceholderType
 
@@ -9,3 +15,64 @@ type (
 	// PlaceholderType represents a placeholder type.
 	PlaceholderType = struct{}
 )
+
+// Repr returns the string representation of v.
+func Repr(v interface{}) string {
+	if v == nil {
+		return ""
+	}
+
+	// if func (v *Type) String() string, we can't use Elem()
+	switch vt := v.(type) {
+	case fmt.Stringer:
+		return vt.String()
+	}
+
+	val := reflect.ValueOf(v)
+	if val.Kind() == reflect.Ptr && !val.IsNil() {
+		val = val.Elem()
+	}
+
+	return reprOfValue(val)
+}
+
+func reprOfValue(val reflect.Value) string {
+	switch vt := val.Interface().(type) {
+	case bool:
+		return strconv.FormatBool(vt)
+	case error:
+		return vt.Error()
+	case float32:
+		return strconv.FormatFloat(float64(vt), 'f', -1, 32)
+	case float64:
+		return strconv.FormatFloat(vt, 'f', -1, 64)
+	case fmt.Stringer:
+		return vt.String()
+	case int:
+		return strconv.Itoa(vt)
+	case int8:
+		return strconv.Itoa(int(vt))
+	case int16:
+		return strconv.Itoa(int(vt))
+	case int32:
+		return strconv.Itoa(int(vt))
+	case int64:
+		return strconv.FormatInt(vt, 10)
+	case string:
+		return vt
+	case uint:
+		return strconv.FormatUint(uint64(vt), 10)
+	case uint8:
+		return strconv.FormatUint(uint64(vt), 10)
+	case uint16:
+		return strconv.FormatUint(uint64(vt), 10)
+	case uint32:
+		return strconv.FormatUint(uint64(vt), 10)
+	case uint64:
+		return strconv.FormatUint(vt, 10)
+	case []byte:
+		return string(vt)
+	default:
+		return fmt.Sprint(val.Interface())
+	}
+}

core/lang/lang_test.go

@@ -0,0 +1,131 @@
+package lang
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestRepr(t *testing.T) {
+	var (
+		f32 float32 = 1.1
+		f64         = 2.2
+		i8  int8    = 1
+		i16 int16   = 2
+		i32 int32   = 3
+		i64 int64   = 4
+		u8  uint8   = 5
+		u16 uint16  = 6
+		u32 uint32  = 7
+		u64 uint64  = 8
+	)
+	tests := []struct {
+		v      interface{}
+		expect string
+	}{
+		{
+			nil,
+			"",
+		},
+		{
+			mockStringable{},
+			"mocked",
+		},
+		{
+			new(mockStringable),
+			"mocked",
+		},
+		{
+			newMockPtr(),
+			"mockptr",
+		},
+		{
+			&mockOpacity{
+				val: 1,
+			},
+			"{1}",
+		},
+		{
+			true,
+			"true",
+		},
+		{
+			false,
+			"false",
+		},
+		{
+			f32,
+			"1.1",
+		},
+		{
+			f64,
+			"2.2",
+		},
+		{
+			i8,
+			"1",
+		},
+		{
+			i16,
+			"2",
+		},
+		{
+			i32,
+			"3",
+		},
+		{
+			i64,
+			"4",
+		},
+		{
+			u8,
+			"5",
+		},
+		{
+			u16,
+			"6",
+		},
+		{
+			u32,
+			"7",
+		},
+		{
+			u64,
+			"8",
+		},
+		{
+			[]byte(`abcd`),
+			"abcd",
+		},
+		{
+			mockOpacity{val: 1},
+			"{1}",
+		},
+	}
+
+	for _, test := range tests {
+		t.Run(test.expect, func(t *testing.T) {
+			assert.Equal(t, test.expect, Repr(test.v))
+		})
+	}
+}
+
+type mockStringable struct{}
+
+func (m mockStringable) String() string {
+	return "mocked"
+}
+
+type mockPtr struct{}
+
+func newMockPtr() *mockPtr {
+	return new(mockPtr)
+}
+
+func (m *mockPtr) String() string {
+	return "mockptr"
+}
+
+type mockOpacity struct {
+	val int
+}