Make flag mutually exclusive

main.go

@@ -10,7 +10,6 @@ import (
 	"github.com/urfave/cli/v3"
 )
 
-
 var (
 	version = "dev"
 	commit  = "none"
@@ -30,6 +29,7 @@ func main() {
 		Flags:                 util.Flags,
 		EnableShellCompletion: true,
 		HideHelpCommand:       true,
+		Before:                util.CheckMutuallyExclusiveTitleFlags,
 		Action:                util.RunMark,
 	}
 

util/cli_test.go

@@ -0,0 +1,52 @@
+package util
+
+import (
+	"context"
+	"testing"
+
+	"github.com/urfave/cli/v3"
+)
+
+func runWithArgs(args []string) error {
+	cmd := &cli.Command{
+		Flags: []cli.Flag{
+			&cli.BoolFlag{Name: "title-from-h1"},
+			&cli.BoolFlag{Name: "title-from-filename"},
+		},
+		Before: CheckMutuallyExclusiveTitleFlags,
+		Action: func(ctx context.Context, cmd *cli.Command) error {
+			return nil
+		},
+	}
+	return cmd.Run(context.Background(), args)
+}
+
+func TestCheckMutuallyExclusiveTitleFlags(t *testing.T) {
+	t.Run("neither flag set", func(t *testing.T) {
+		err := runWithArgs([]string{"cmd"})
+		if err != nil {
+			t.Errorf("unexpected error: %v", err)
+		}
+	})
+
+	t.Run("only title-from-h1 set", func(t *testing.T) {
+		err := runWithArgs([]string{"cmd", "--title-from-h1"})
+		if err != nil {
+			t.Errorf("unexpected error: %v", err)
+		}
+	})
+
+	t.Run("only title-from-filename set", func(t *testing.T) {
+		err := runWithArgs([]string{"cmd", "--title-from-filename"})
+		if err != nil {
+			t.Errorf("unexpected error: %v", err)
+		}
+	})
+
+	t.Run("both flags set", func(t *testing.T) {
+		err := runWithArgs([]string{"cmd", "--title-from-h1", "--title-from-filename"})
+		if err == nil {
+			t.Errorf("expected error, got nil")
+		}
+	})
+}

util/flags.go

@@ -1,6 +1,9 @@
 package util
 
 import (
+	"context"
+	"errors"
+
 	altsrc "github.com/urfave/cli-altsrc/v3"
 	altsrctoml "github.com/urfave/cli-altsrc/v3/toml"
 	"github.com/urfave/cli/v3"
@@ -58,13 +61,13 @@ var Flags = []cli.Flag{
 	&cli.BoolFlag{
 		Name:    "title-from-h1",
 		Value:   false,
-		Usage:   "extract page title from a leading H1 heading. If no H1 heading on a page exists, then title must be set in the page metadata.",
+		Usage:   "extract page title from a leading H1 heading. If no H1 heading on a page exists, then title must be set in the page metadata. Mutually exclusive with --title-from-filename.",
 		Sources: cli.NewValueSourceChain(cli.EnvVar("MARK_TITLE_FROM_H1"), altsrctoml.TOML("title-from-h1", altsrc.NewStringPtrSourcer(&filename))),
 	},
 	&cli.BoolFlag{
 		Name:    "title-from-filename",
 		Value:   false,
-		Usage:   "use the filename (without extension) as the Confluence page title if no explicit 'Title' header or H1 heading is found.",
+		Usage:   "use the filename (without extension) as the Confluence page title if no explicit page title is set in the metadata. Mutually exclusive with --title-from-h1.",
 		Sources: cli.NewValueSourceChain(cli.EnvVar("MARK_TITLE_FROM_FILENAME"), altsrctoml.TOML("title-from-filename", altsrc.NewStringPtrSourcer(&filename))),
 	},
 	&cli.BoolFlag{
@@ -194,3 +197,11 @@ var Flags = []cli.Flag{
 		Sources: cli.NewValueSourceChain(cli.EnvVar("MARK_FEATURES"), altsrctoml.TOML("features", altsrc.NewStringPtrSourcer(&filename))),
 	},
 }
+
+// CheckMutuallyExclusiveTitleFlags checks if both title-from-h1 and title-from-filename are set
+func CheckMutuallyExclusiveTitleFlags(context context.Context, command *cli.Command) (context.Context, error) {
+	if command.Bool("title-from-h1") && command.Bool("title-from-filename") {
+		return context, errors.New("flags --title-from-h1 and --title-from-filename are mutually exclusive. Please specify only one")
+	}
+	return context, nil
+}