Encapsulate ExitCoder check into a lil func

app.go

@@ -157,10 +157,7 @@ func (a *App) Run(arguments []string) (err error) {
 		if a.OnUsageError != nil {
 			err := a.OnUsageError(context, err, false)
 			if err != nil {
-				if exitErr, ok := err.(ExitCoder); ok {
-					os.Exit(exitErr.ExitCode())
-					panic("unreachable")
-				}
+				HandleExitCoder(err)
 			}
 			return err
 		} else {
@@ -198,12 +195,7 @@ func (a *App) Run(arguments []string) (err error) {
 		if err != nil {
 			fmt.Fprintf(a.Writer, "%v\n\n", err)
 			ShowAppHelp(context)
-
-			if exitErr, ok := err.(ExitCoder); ok {
-				os.Exit(exitErr.ExitCode())
-				panic("unreachable")
-			}
-
+			HandleExitCoder(err)
 			return err
 		}
 	}
@@ -219,31 +211,11 @@ func (a *App) Run(arguments []string) (err error) {
 
 	// Run default Action
 	err = a.Action(context)
-
-	if exitErr, ok := err.(ExitCoder); ok {
-		os.Exit(exitErr.ExitCode())
-		panic("unreachable")
-	}
+	HandleExitCoder(err)
 
 	return err
 }
 
-// Another entry point to the cli app, takes care of passing arguments and error handling
-func (a *App) RunAndExitOnError() {
-	err := a.Run(os.Args)
-	if exitErr, ok := err.(ExitCoder); ok {
-		os.Exit(exitErr.ExitCode())
-		panic("unreachable")
-	}
-
-	if err != nil {
-		os.Exit(DefaultErrorExitCode)
-		panic("unreachable")
-	}
-
-	os.Exit(DefaultSuccessExitCode)
-}
-
 // Invokes the subcommand given the context, parses ctx.Args() to generate command-specific flags
 func (a *App) RunAsSubcommand(ctx *Context) (err error) {
 	// append help to commands
@@ -295,10 +267,7 @@ func (a *App) RunAsSubcommand(ctx *Context) (err error) {
 	if err != nil {
 		if a.OnUsageError != nil {
 			err = a.OnUsageError(context, err, true)
-			if exitErr, ok := err.(ExitCoder); ok {
-				os.Exit(exitErr.ExitCode())
-				panic("unreachable")
-			}
+			HandleExitCoder(err)
 			return nil
 		} else {
 			fmt.Fprintf(a.Writer, "%s\n\n", "Incorrect Usage.")
@@ -321,10 +290,7 @@ func (a *App) RunAsSubcommand(ctx *Context) (err error) {
 		defer func() {
 			afterErr := a.After(context)
 			if afterErr != nil {
-				if exitErr, ok := afterErr.(ExitCoder); ok {
-					os.Exit(exitErr.ExitCode())
-					panic("unreachable")
-				}
+				HandleExitCoder(err)
 				if err != nil {
 					err = NewMultiError(err, afterErr)
 				} else {
@@ -337,10 +303,7 @@ func (a *App) RunAsSubcommand(ctx *Context) (err error) {
 	if a.Before != nil {
 		err = a.Before(context)
 		if err != nil {
-			if exitErr, ok := err.(ExitCoder); ok {
-				os.Exit(exitErr.ExitCode())
-				panic("unreachable")
-			}
+			HandleExitCoder(err)
 			return err
 		}
 	}

command.go

@@ -3,7 +3,6 @@ package cli
 import (
 	"fmt"
 	"io/ioutil"
-	"os"
 	"sort"
 	"strings"
 )
@@ -125,10 +124,7 @@ func (c Command) Run(ctx *Context) (err error) {
 	if err != nil {
 		if c.OnUsageError != nil {
 			err := c.OnUsageError(ctx, err, false)
-			if exitErr, ok := err.(ExitCoder); ok {
-				os.Exit(exitErr.ExitCode())
-				panic("unreachable")
-			}
+			HandleExitCoder(err)
 			return err
 		} else {
 			fmt.Fprintln(ctx.App.Writer, "Incorrect Usage.")
@@ -160,10 +156,7 @@ func (c Command) Run(ctx *Context) (err error) {
 		defer func() {
 			afterErr := c.After(context)
 			if afterErr != nil {
-				if exitErr, ok := afterErr.(ExitCoder); ok {
-					os.Exit(exitErr.ExitCode())
-					panic("unreachable")
-				}
+				HandleExitCoder(err)
 				if err != nil {
 					err = NewMultiError(err, afterErr)
 				} else {
@@ -179,10 +172,7 @@ func (c Command) Run(ctx *Context) (err error) {
 			fmt.Fprintln(ctx.App.Writer, err)
 			fmt.Fprintln(ctx.App.Writer)
 			ShowCommandHelp(ctx, c.Name)
-			if exitErr, ok := err.(ExitCoder); ok {
-				os.Exit(exitErr.ExitCode())
-				panic("unreachable")
-			}
+			HandleExitCoder(err)
 			return err
 		}
 	}
@@ -190,10 +180,7 @@ func (c Command) Run(ctx *Context) (err error) {
 	context.Command = c
 	err = c.Action(context)
 	if err != nil {
-		if exitErr, ok := err.(ExitCoder); ok {
-			os.Exit(exitErr.ExitCode())
-			panic("unreachable")
-		}
+		HandleExitCoder(err)
 	}
 	return err
 }

errors.go

@@ -2,6 +2,7 @@ package cli
 
 import (
 	"fmt"
+	"os"
 	"strings"
 )
 
@@ -49,3 +50,11 @@ func (ee *ExitError) String() string {
 func (ee *ExitError) ExitCode() int {
 	return ee.exitCode
 }
+
+// HandleExitCoder checks if the error fulfills the ExitCoder interface, and if
+// so calls os.Exit with the given exit code.
+func HandleExitCoder(err error) {
+	if exitErr, ok := err.(ExitCoder); ok {
+		os.Exit(exitErr.ExitCode())
+	}
+}