feat(valuer): add string valuer (#7554)

pkg/valuer/string.go

@@ -0,0 +1,69 @@
+package valuer
+
+import (
+	"database/sql/driver"
+	"encoding/json"
+	"fmt"
+	"reflect"
+	"strings"
+)
+
+var _ Valuer = (*String)(nil)
+
+type String struct {
+	val string
+}
+
+func NewString(val string) String {
+	return String{val: strings.ToLower(strings.TrimSpace(val))}
+}
+
+func (enum String) IsZero() bool {
+	return enum.val == ""
+}
+
+func (enum String) StringValue() string {
+	return enum.val
+}
+
+func (enum String) String() string {
+	return enum.val
+}
+
+func (enum String) MarshalJSON() ([]byte, error) {
+	return json.Marshal(enum.StringValue())
+}
+
+func (enum *String) UnmarshalJSON(data []byte) error {
+	var str string
+	if err := json.Unmarshal(data, &str); err != nil {
+		return err
+	}
+
+	*enum = NewString(str)
+	return nil
+}
+
+func (enum String) Value() (driver.Value, error) {
+	return enum.StringValue(), nil
+}
+
+func (enum *String) Scan(val interface{}) error {
+	if enum == nil {
+		return fmt.Errorf("string: (nil \"%s\")", reflect.TypeOf(enum).String())
+	}
+
+	if val == nil {
+		// Return an empty string
+		*enum = NewString("")
+		return nil
+	}
+
+	str, ok := val.(string)
+	if !ok {
+		return fmt.Errorf("string: (non-string \"%s\")", reflect.TypeOf(val).String())
+	}
+
+	*enum = NewString(str)
+	return nil
+}

pkg/valuer/uuid.go

@@ -65,6 +65,10 @@ func (enum UUID) StringValue() string {
 	return enum.val.String()
 }
 
+func (enum UUID) String() string {
+	return enum.val.String()
+}
+
 func (enum UUID) MarshalJSON() ([]byte, error) {
 	return json.Marshal(enum.StringValue())
 }

pkg/valuer/valuer.go

@@ -4,19 +4,28 @@ import (
 	"database/sql"
 	"database/sql/driver"
 	"encoding/json"
+	"fmt"
 )
 
 type Valuer interface {
 	// IsZero returns true if the value is considered empty or zero
 	IsZero() bool
+
 	// StringValue returns the string representation of the value
 	StringValue() string
+
 	// MarshalJSON returns the JSON encoding of the value.
 	json.Marshaler
+
 	// UnmarshalJSON returns the JSON decoding of the value.
 	json.Unmarshaler
+
 	// Scan into underlying struct from a database driver's value
 	sql.Scanner
+
 	// Convert the struct to a database driver's value
 	driver.Valuer
+
+	// Implement fmt.Stringer to allow the value to be printed as a string
+	fmt.Stringer
 }