fix: reset flags' value to default if flags have been parsed

command.go

@@ -1830,6 +1830,12 @@ func (c *Command) ParseFlags(args []string) error {
 	// do it here after merging all flags and just before parse
 	c.Flags().ParseErrorsWhitelist = flag.ParseErrorsWhitelist(c.FParseErrWhitelist)
 
+	// if flag has been parsed, we should reset flags' value to default
+	if c.Flags().Parsed() {
+		c.Flags().Visit(func(f *flag.Flag) {
+			f.Value.Set(f.DefValue)
+		})
+	}
 	err := c.Flags().Parse(args)
 	// Print warnings if they occurred (e.g. deprecated flag messages).
 	if c.flagErrorBuf.Len()-beforeErrorBufLen > 0 && err == nil {

flag_groups_test.go

@@ -15,6 +15,7 @@
 package cobra
 
 import (
+	"fmt"
 	"strings"
 	"testing"
 )
@@ -193,3 +194,54 @@ func TestValidateFlagGroups(t *testing.T) {
 		})
 	}
 }
+
+func TestSetArgs(t *testing.T) {
+	getCMD := func() *Command {
+		cmd := &Command{
+			Use: "testcmd",
+			RunE: func(cmd *Command, args []string) error {
+				a, _ := cmd.Flags().GetBool("a")
+				b, _ := cmd.Flags().GetBool("b")
+				c, _ := cmd.Flags().GetBool("c")
+				switch {
+				case a && b, a && c, b && c:
+					return fmt.Errorf("a,b,c only one could be true")
+				}
+				return nil
+			},
+		}
+		f := cmd.Flags()
+		f.BoolP("a", "a", false, "a,b,c only one could be true")
+		f.BoolP("b", "b", false, "a,b,c only one could be true")
+		f.Bool("c", false, "a,b,c only one could be true")
+		return cmd
+	}
+
+	cmd := getCMD()
+
+	// step 1
+	cmd.SetArgs([]string{
+		"--a=true",
+	})
+	assertNoErr(t, cmd.Execute())
+	// step 2
+	cmd.SetArgs([]string{
+		"--b=true",
+	})
+	t.Log(cmd.Flags().Changed("a"))
+	assertNoErr(t, cmd.Execute())
+
+	// step 3
+	cmd.SetArgs([]string{
+		"--c=true",
+	})
+	assertNoErr(t, cmd.Execute())
+
+	// step 4
+	cmd.SetArgs([]string{
+		"--a=false",
+		"--b=false",
+		"--c=true",
+	})
+	assertNoErr(t, cmd.Execute())
+}