feat: improve error message when detecting conflicting flags

cmd/oras/internal/errors/errors.go

@@ -21,6 +21,7 @@ import (
 	"strings"
 
 	"github.com/spf13/cobra"
+	"github.com/spf13/pflag"
 	"oras.land/oras-go/v2/registry/remote/auth"
 	"oras.land/oras-go/v2/registry/remote/errcode"
 )
@@ -156,3 +157,27 @@ func NewErrEmptyTagOrDigest(ref string, cmd *cobra.Command, needsTag bool) error
 		Recommendation: fmt.Sprintf(`Please specify a reference in the form of %s. Run "%s -h" for more options and examples`, form, cmd.CommandPath()),
 	}
 }
+
+// CheckMutuallyExclusiveFlags checks if any mutually exclusive flags are used
+// at the same time, returns an error when detecting used exclusive flags. It
+// detects the first set of conflict and returns the error without checking
+// the rest of the flag sets.
+func CheckMutuallyExclusiveFlags(fs *pflag.FlagSet, exclusiveFlagSets ...[]string) error {
+	var checkConflict = func(exclusiveFlagSet []string) []string {
+		changedFlags := []string{}
+		for _, flagName := range exclusiveFlagSet {
+			if fs.Changed(flagName) {
+				changedFlags = append(changedFlags, fmt.Sprintf("--%s", flagName))
+			}
+		}
+		return changedFlags
+	}
+	for _, set := range exclusiveFlagSets {
+		changedFlags := checkConflict(set)
+		if len(changedFlags) >= 2 {
+			flags := strings.Join(changedFlags, ", ")
+			return fmt.Errorf("%s cannot be used at the same time", flags)
+		}
+	}
+	return nil
+}

cmd/oras/internal/option/remote.go

@@ -149,8 +149,9 @@ func (opts *Remote) Parse(cmd *cobra.Command) error {
 	if cmd.Flags().Lookup(passwordFromStdinFlag) != nil {
 		passwordAndIdTokenFlags = append(passwordAndIdTokenFlags, passwordFromStdinFlag)
 	}
-	cmd.MarkFlagsMutuallyExclusive(usernameAndIdTokenFlags...)
-	cmd.MarkFlagsMutuallyExclusive(passwordAndIdTokenFlags...)
+	if err := oerrors.CheckMutuallyExclusiveFlags(cmd.Flags(), usernameAndIdTokenFlags, passwordAndIdTokenFlags); err != nil {
+		return err
+	}
 	if err := opts.parseCustomHeaders(); err != nil {
 		return err
 	}