Allow Ignoring Usage Errors

README.md

@@ -1306,6 +1306,7 @@ func main() {
       fmt.Fprintf(c.App.Writer, "WRONG: %#v\n", err)
       return nil
     },
+    IgnoreUsageError: true,
     Action: func(c *cli.Context) error {
       cli.DefaultAppComplete(c)
       cli.HandleExitCoder(errors.New("not an exit coder, though"))

app.go

@@ -51,6 +51,8 @@ type App struct {
 	Action ActionFunc
 	// Execute this function if the proper command cannot be found
 	CommandNotFound CommandNotFoundFunc
+	// Ignore usage errors to be handled later
+	IgnoreUsageError bool
 	// Execute this function if an usage error occurs
 	OnUsageError OnUsageErrorFunc
 	// Compilation date
@@ -187,7 +189,7 @@ func (a *App) Run(arguments []string) (err error) {
 		}
 	}
 
-	if err != nil {
+	if err != nil && !a.IgnoreUsageError {
 		if a.OnUsageError != nil {
 			err := a.OnUsageError(context, err, false)
 			HandleExitCoder(err)

app_test.go

@@ -1485,3 +1485,24 @@ func TestApp_OnUsageError_WithWrongFlagValue_ForSubcommand(t *testing.T) {
 		t.Errorf("Expect an intercepted error, but got \"%v\"", err)
 	}
 }
+
+func TestApp_IgnoreOnUsageError(t *testing.T) {
+	app := &App{
+		Flags: []Flag{
+			&IntFlag{Name: "flag"},
+		},
+		Action: func(c *Context) error {
+			return nil
+		},
+		OnUsageError: func(c *Context, err error, isSubcommand bool) error {
+			t.Fatalf("Shouldn't throw error")
+			return errors.New("intercepted: " + err.Error())
+		},
+		IgnoreUsageError: true,
+	}
+
+	err := app.Run([]string{"foo", "--wrong-flag"})
+	if err != nil {
+		t.Fatalf("expected to not receive error, but got: \"%v\"", err)
+	}
+}