fix: fix DumpToFile() error on go1.15, add some tests

config_test.go

@@ -403,6 +403,24 @@ func TestJSONAllowComments(t *testing.T) {
 	JSONAllowComments = old
 }
 
+func TestSaveFileOnSet(t *testing.T) {
+	old := JSONMarshalIndent
+	JSONMarshalIndent = "  "
+	defer func() {
+		JSONMarshalIndent = old
+	}()
+
+	is := assert.New(t)
+	c := New("test")
+	c.WithOptions(SaveFileOnSet("testdata/config.bak.json", JSON))
+
+	err := c.LoadStrings(JSON, jsonStr)
+	is.Nil(err)
+
+	is.NoError(c.Set("new-key", "new-value"))
+	is.Equal("new-value", c.Get("new-key"))
+}
+
 func TestMapStringStringParseEnv(t *testing.T) {
 	is := assert.New(t)
 	c := New("test")

export.go

@@ -155,7 +155,6 @@ func (c *Config) DumpToFile(fileName string, format string) (err error) {
 		return
 	}
 
-	// is empty
 	if len(c.data) == 0 {
 		return
 	}
@@ -167,6 +166,15 @@ func (c *Config) DumpToFile(fileName string, format string) (err error) {
 	}
 
 	// write content to out
-	//num, _ := fmt.Fprintln(out, string(encoded))
-	return os.WriteFile(fileName, encoded, os.ModePerm)
+	fsFlags := os.O_CREATE | os.O_WRONLY | os.O_TRUNC
+	f, err := os.OpenFile(fileName, fsFlags, os.ModePerm)
+	if err != nil {
+		return err
+	}
+
+	_, err = f.Write(encoded)
+	if err1 := f.Close(); err1 != nil && err == nil {
+		err = err1
+	}
+	return err
 }

options.go

@@ -1,8 +1,9 @@
 package config
 
 import (
-	"github.com/mitchellh/mapstructure"
 	"strings"
+
+	"github.com/mitchellh/mapstructure"
 )
 
 // there are some event names for config data changed.
@@ -91,8 +92,8 @@ func Delimiter(sep byte) func(*Options) {
 	}
 }
 
-// WithSetSaveFile set hook func
-func WithSetSaveFile(fileName string, format string) func(options *Options) {
+// SaveFileOnSet set hook func
+func SaveFileOnSet(fileName string, format string) func(options *Options) {
 	return func(opts *Options) {
 		opts.HookFunc = func(event string, c *Config) {
 			if strings.HasPrefix(event, "set.") {