Aggregate errors from Before/After

Previously `After` would overwrite any error from `Before`.

app.go

@@ -132,10 +132,14 @@ func (a *App) Run(arguments []string) (err error) {
 
 	if a.After != nil {
 		defer func() {
-			// err is always nil here.
-			// There is a check to see if it is non-nil
-			// just few lines before.
-			err = a.After(context)
+			afterErr := a.After(context)
+			if afterErr != nil {
+				if err != nil {
+					err = NewMultiError(err, afterErr)
+				} else {
+					err = afterErr
+				}
+			}
 		}()
 	}
 
@@ -225,10 +229,14 @@ func (a *App) RunAsSubcommand(ctx *Context) (err error) {
 
 	if a.After != nil {
 		defer func() {
-			// err is always nil here.
-			// There is a check to see if it is non-nil
-			// just few lines before.
-			err = a.After(context)
+			afterErr := a.After(context)
+			if afterErr != nil {
+				if err != nil {
+					err = NewMultiError(err, afterErr)
+				} else {
+					err = afterErr
+				}
+			}
 		}()
 	}
 

app_test.go

@@ -709,3 +709,45 @@ func TestApp_Run_CommandWithSubcommandHasHelpTopic(t *testing.T) {
 		}
 	}
 }
+
+func TestApp_Run_DoesNotOverwriteErrorFromBefore(t *testing.T) {
+	app := cli.NewApp()
+	app.Action = func(c *cli.Context) {}
+	app.Before = func(c *cli.Context) error { return fmt.Errorf("before error") }
+	app.After = func(c *cli.Context) error { return fmt.Errorf("after error") }
+
+	err := app.Run([]string{"foo"})
+	if err == nil {
+		t.Fatalf("expected to recieve error from Run, got none")
+	}
+
+	if !strings.Contains(err.Error(), "before error") {
+		t.Errorf("expected text of error from Before method, but got none in \"%v\"", err)
+	}
+	if !strings.Contains(err.Error(), "after error") {
+		t.Errorf("expected text of error from After method, but got none in \"%v\"", err)
+	}
+}
+
+func TestApp_Run_SubcommandDoesNotOverwriteErrorFromBefore(t *testing.T) {
+	app := cli.NewApp()
+	app.Commands = []cli.Command{
+		cli.Command{
+			Name:   "bar",
+			Before: func(c *cli.Context) error { return fmt.Errorf("before error") },
+			After:  func(c *cli.Context) error { return fmt.Errorf("after error") },
+		},
+	}
+
+	err := app.Run([]string{"foo", "bar"})
+	if err == nil {
+		t.Fatalf("expected to recieve error from Run, got none")
+	}
+
+	if !strings.Contains(err.Error(), "before error") {
+		t.Errorf("expected text of error from Before method, but got none in \"%v\"", err)
+	}
+	if !strings.Contains(err.Error(), "after error") {
+		t.Errorf("expected text of error from After method, but got none in \"%v\"", err)
+	}
+}

cli.go

@@ -17,3 +17,24 @@
 //     app.Run(os.Args)
 //   }
 package cli
+
+import (
+	"strings"
+)
+
+type MultiError struct {
+	Errors []error
+}
+
+func NewMultiError(err ...error) MultiError {
+	return MultiError{Errors: err}
+}
+
+func (m MultiError) Error() string {
+	errs := make([]string, len(m.Errors))
+	for i, err := range m.Errors {
+		errs[i] = err.Error()
+	}
+
+	return strings.Join(errs, "\n")
+}