Merge pull request #766 from ydb-platform/is-optional

* Added `table/types.IsOptional()` helper

Author: asmyasnikov

CHANGELOG.md

@@ -1,3 +1,5 @@
+* Added `table/types.IsOptional()` helper
+
 ## v3.48.2
 * Refactored tests
 

table/types/cast.go

@@ -18,6 +18,17 @@ func CastTo(v Value, dst interface{}) error {
 	return value.CastTo(v, dst)
 }
 
+// IsOptional checks if type is optional and returns innerType if it is.
+func IsOptional(t Type) (isOptional bool, innerType Type) {
+	if optionalType, isOptional := t.(interface {
+		IsOptional()
+		InnerType() Type
+	}); isOptional {
+		return isOptional, optionalType.InnerType()
+	}
+	return false, nil
+}
+
 // ToDecimal returns Decimal struct from abstract Value
 func ToDecimal(v Value) (*Decimal, error) {
 	if valuer, isDecimalValuer := v.(value.DecimalValuer); isDecimalValuer {

table/types/cast_test.go

@@ -7,6 +7,41 @@ import (
 	"github.com/stretchr/testify/require"
 )
 
+func TestIsOptional(t *testing.T) {
+	for _, tt := range []struct {
+		t          Type
+		isOptional bool
+		innerType  Type
+	}{
+		{
+			t:          nil,
+			isOptional: false,
+			innerType:  nil,
+		},
+		{
+			t:          TypeBool,
+			isOptional: false,
+			innerType:  nil,
+		},
+		{
+			t:          Optional(TypeBool),
+			isOptional: true,
+			innerType:  TypeBool,
+		},
+		{
+			t:          Optional(Optional(TypeBool)),
+			isOptional: true,
+			innerType:  Optional(TypeBool),
+		},
+	} {
+		t.Run("", func(t *testing.T) {
+			isOptional, innerType := IsOptional(tt.t)
+			require.Equal(t, tt.isOptional, isOptional)
+			require.Equal(t, tt.innerType, innerType)
+		})
+	}
+}
+
 func TestToDecimal(t *testing.T) {
 	for _, tt := range []struct {
 		v   Value