🎁 Custom error handler (#3)

* Custom error handler

* Call error handler only if the error occurs

Author: cardil

app.go

@@ -14,10 +14,15 @@ var ErrNoRootCommand = errors.New("no root command provided")
 // App represents a command line application.
 type App struct {
 	CobraProvider
+	ErrorHandler
 	Exit func(code int)
 	root *cobra.Command
 }
 
+// ErrorHandler is a function that will be used to handle the errors. If true
+// is returned, the default error handling will not be used.
+type ErrorHandler func(err error) bool
+
 // CobraProvider is used to provide a Cobra command.
 type CobraProvider interface {
 	Command() *cobra.Command
@@ -33,8 +38,12 @@ func New(cp CobraProvider) *App {
 
 // ExecuteOrDie will execute the application or perform os.Exit in case of error.
 func (a *App) ExecuteOrDie(options ...Option) {
-	if err := a.Execute(options...); err != nil {
-		a.Exit(retcode.Calc(err))
+	err := a.Execute(options...)
+	if err == nil {
+		return
+	}
+	if a.ErrorHandler == nil || !a.ErrorHandler(err) {
+		a.defaultErrorHandler(err)
 	}
 }
 
@@ -64,3 +73,9 @@ func (a *App) init() error {
 	}
 	return nil
 }
+
+func (a *App) defaultErrorHandler(err error) {
+	if err != nil {
+		a.Exit(retcode.Calc(err))
+	}
+}

app_test.go

@@ -14,6 +14,7 @@ import (
 func TestExecuteOrDie(t *testing.T) {
 	var buf bytes.Buffer
 	var retcode int
+	var err error
 	commandline.New(new(testApp)).ExecuteOrDie(
 		commandline.WithCommand(func(cmd *cobra.Command) {
 			cmd.SetOut(&buf)
@@ -23,9 +24,14 @@ func TestExecuteOrDie(t *testing.T) {
 		commandline.WithExit(func(code int) {
 			retcode = code
 		}),
+		commandline.WithErrorHandler(func(merr error) bool {
+			err = merr
+			return false
+		}),
 	)
 	assert.Equal(t, `example Input: ["arg1" "arg2"]`, buf.String())
 	assert.Equal(t, 133, retcode)
+	assert.Assert(t, err != nil)
 }
 
 func TestExit(t *testing.T) {

options.go

@@ -41,6 +41,13 @@ func WithCommand(fn func(cmd *cobra.Command)) Option {
 	}
 }
 
+// WithErrorHandler will allow changing the default error handler.
+func WithErrorHandler(fn ErrorHandler) Option {
+	return func(app *App) {
+		app.ErrorHandler = fn
+	}
+}
+
 // WithExit creates an option which sets the exit function.
 func WithExit(fn func(code int)) Option {
 	return func(app *App) {