Fix panic handling and add a new exit code and a test for panics (#2997)

Because we started calling os.Exit() in a defer statement, we circumvented the regular handling of panics that bubble up to the top by the Go runtime. I could have removed the os.Exit() call from the defer, but handling panics ourselves in this way allows us to handle them exactly how we want, assign them their own unique exit code, and test the whole thing with an e2e test.

cmd/root.go

@@ -6,6 +6,7 @@ import (
 	"fmt"
 	"io"
 	stdlog "log"
+	"runtime/debug"
 	"strconv"
 	"strings"
 	"sync"
@@ -17,6 +18,7 @@ import (
 
 	"go.k6.io/k6/cmd/state"
 	"go.k6.io/k6/errext"
+	"go.k6.io/k6/errext/exitcodes"
 	"go.k6.io/k6/lib/consts"
 	"go.k6.io/k6/log"
 )
@@ -88,6 +90,17 @@ func (c *rootCommand) execute() {
 		c.globalState.OSExit(exitCode)
 	}()
 
+	defer func() {
+		if r := recover(); r != nil {
+			exitCode = int(exitcodes.GoPanic)
+			err := fmt.Errorf("unexpected k6 panic: %s\n%s", r, debug.Stack())
+			if c.loggerIsRemote {
+				c.globalState.FallbackLogger.Error(err)
+			}
+			c.globalState.Logger.Error(err)
+		}
+	}()
+
 	err := c.cmd.Execute()
 	if err == nil {
 		exitCode = 0

cmd/root_test.go

@@ -5,8 +5,10 @@ import (
 	"testing"
 
 	"github.com/sirupsen/logrus"
+	"github.com/spf13/cobra"
 	"github.com/stretchr/testify/assert"
 	"go.k6.io/k6/cmd/tests"
+	"go.k6.io/k6/errext/exitcodes"
 	"go.k6.io/k6/lib/testutils"
 )
 
@@ -37,3 +39,25 @@ func TestDeprecatedOptionWarning(t *testing.T) {
 	assert.False(t, testutils.LogContains(logMsgs, logrus.InfoLevel, "logformat"))
 	assert.Contains(t, ts.Stdout.String(), `--logformat has been deprecated`)
 }
+
+func TestPanicHandling(t *testing.T) {
+	t.Parallel()
+
+	ts := tests.NewGlobalTestState(t)
+	ts.CmdArgs = []string{"k6", "panic"}
+	ts.ExpectedExitCode = int(exitcodes.GoPanic)
+
+	rootCmd := newRootCommand(ts.GlobalState)
+	rootCmd.cmd.AddCommand(&cobra.Command{
+		Use: "panic",
+		RunE: func(cmd *cobra.Command, args []string) error {
+			panic("oh no, oh no, oh no,no,no,no,no")
+		},
+	})
+	rootCmd.execute()
+
+	t.Log(ts.Stderr.String())
+	logMsgs := ts.LoggerHook.Drain()
+	assert.True(t, testutils.LogContains(logMsgs, logrus.ErrorLevel, "unexpected k6 panic: oh no"))
+	assert.True(t, testutils.LogContains(logMsgs, logrus.ErrorLevel, "cmd.TestPanicHandling")) // check stacktrace
+}

errext/exitcodes/codes.go

@@ -20,4 +20,5 @@ const (
 	CannotStartRESTAPI       ExitCode = 106
 	ScriptException          ExitCode = 107
 	ScriptAborted            ExitCode = 108
+	GoPanic                  ExitCode = 109
 )