Recover panic in the RunWith wrapper and log it to stderr and refactor (

elastic#6011)

the cli_test tests.

libbeat/common/cli/cli.go

@@ -3,15 +3,25 @@ package cli
 import (
 	"fmt"
 	"os"
+	"runtime/debug"
 
 	"github.com/spf13/cobra"
 )
 
+func exitOnPanic() {
+	if r := recover(); r != nil {
+		fmt.Fprintf(os.Stderr, "panic: %s\n", r)
+		debug.PrintStack()
+		os.Exit(1)
+	}
+}
+
 // RunWith wrap cli function with an error handler instead of having the code exit early.
 func RunWith(
 	fn func(cmd *cobra.Command, args []string) error,
 ) func(cmd *cobra.Command, args []string) {
 	return func(cmd *cobra.Command, args []string) {
+		defer exitOnPanic()
 		if err := fn(cmd, args); err != nil {
 			fmt.Fprintln(os.Stderr, err.Error())
 			os.Exit(1)

libbeat/common/cli/cli_test.go

@@ -11,51 +11,69 @@ import (
 	"github.com/stretchr/testify/assert"
 )
 
-func funcWithError() {
-	var cmd *cobra.Command
-	var args []string
-	RunWith(func(cmd *cobra.Command, args []string) error {
-		return fmt.Errorf("Something bad")
-	})(cmd, args)
-}
+func runCli(testName string) (*bytes.Buffer, error) {
+	cmd := exec.Command(os.Args[0], "-test.run="+testName)
+	cmd.Env = append(os.Environ(), "TEST_RUNWITH=1")
+	stderr := new(bytes.Buffer)
+	cmd.Stderr = stderr
 
-func funcWithoutError() {
-	var cmd *cobra.Command
-	var args []string
-	RunWith(func(cmd *cobra.Command, args []string) error {
-		return nil
-	})(cmd, args)
+	err := cmd.Run()
+	return stderr, err
 }
 
 // Example taken from slides from Andrew Gerrand
 // https://talks.golang.org/2014/testing.slide#23
 func TestExitWithError(t *testing.T) {
 	if os.Getenv("TEST_RUNWITH") == "1" {
-		funcWithError()
-		return
+		func() {
+			var cmd *cobra.Command
+			var args []string
+			RunWith(func(cmd *cobra.Command, args []string) error {
+				return fmt.Errorf("Something bad")
+			})(cmd, args)
+			return
+		}()
 	}
-	cmd := exec.Command(os.Args[0], "-test.run=TestExitWithError")
-	cmd.Env = append(os.Environ(), "TEST_RUNWITH=1")
-	bufError := new(bytes.Buffer)
-	cmd.Stderr = bufError
-	err := cmd.Run()
+
+	stderr, err := runCli("TestExitWithError")
 	if assert.Error(t, err) {
 		assert.Equal(t, err.Error(), "exit status 1")
 	}
-	assert.Equal(t, "Something bad\n", bufError.String())
+	assert.Equal(t, "Something bad\n", stderr.String())
 }
 
 func TestExitWithoutError(t *testing.T) {
 	if os.Getenv("TEST_RUNWITH") == "1" {
-		funcWithoutError()
+		func() {
+			var cmd *cobra.Command
+			var args []string
+			RunWith(func(cmd *cobra.Command, args []string) error {
+				return nil
+			})(cmd, args)
+		}()
 		return
 	}
 
-	cmd := exec.Command(os.Args[0], "-test.run=TestExitWithoutError")
-	cmd.Env = append(os.Environ(), "TEST_RUNWITH=1")
-	bufError := new(bytes.Buffer)
-	cmd.Stderr = bufError
-	err := cmd.Run()
+	stderr, err := runCli("TestExitWithoutError")
 	assert.NoError(t, err)
-	assert.Equal(t, "", bufError.String())
+	assert.Equal(t, "", stderr.String())
+}
+
+func TestExitWithPanic(t *testing.T) {
+	if os.Getenv("TEST_RUNWITH") == "1" {
+		func() {
+			var cmd *cobra.Command
+			var args []string
+			RunWith(func(cmd *cobra.Command, args []string) error {
+				panic("something really bad happened")
+			})(cmd, args)
+		}()
+		return
+	}
+
+	stderr, err := runCli("TestExitWithPanic")
+	if assert.Error(t, err) {
+		assert.Equal(t, err.Error(), "exit status 1")
+	}
+	assert.Contains(t, stderr.String(), "something really bad happened")
 }