backwards compatible RequiredFlag implementation

context.go

@@ -301,10 +301,12 @@ func checkRequiredFlags(flags []Flag, set *flag.FlagSet) error {
 	})
 
 	for _, f := range flags {
-		if f.IsRequired() {
-			key := strings.Split(f.GetName(), ",")[0]
-			if !visited[key] {
-				return fmt.Errorf("Required flag %s not set", f.GetName())
+		if rf, ok := f.(RequiredFlag); ok {
+			if rf.IsRequired() {
+				key := strings.Split(f.GetName(), ",")[0]
+				if !visited[key] {
+					return fmt.Errorf("Required flag %s not set", f.GetName())
+				}
 			}
 		}
 	}

flag.go

@@ -72,10 +72,17 @@ type Flag interface {
 	fmt.Stringer
 	// Apply Flag settings to the given flag set
 	Apply(*flag.FlagSet)
-	IsRequired() bool
 	GetName() string
 }
 
+// RequiredFlag is an interface that allows us to return mark flags as required
+// it allows flags defined in this library to be marked as required in a backwards compatible fashion
+type RequiredFlag interface {
+	Flag
+
+	IsRequired() bool
+}
+
 // errorableFlag is an interface that allows us to return errors during apply
 // it allows flags defined in this library to return errors in a fashion backwards compatible
 // TODO remove in v2 and modify the existing Flag interface to return errors