Function TestFlagCompletionConcurrentRegistration

completions_test.go:2121–2185

This test tries to register flag completion concurrently to make sure the code handles concurrency properly. This was reported as a problem when tests are run concurrently: https://github.com/spf13/cobra/issues/1320 NOTE: this test can sometimes pass even if the code were to not handle concurrency

(t *testing.T)

// it should never fail.  Therefore, if the tests fails sometimes, we will
// still be able to know there is a problem.
func TestFlagCompletionConcurrentRegistration(t *testing.T) {
	rootCmd := &Command{Use: "root", Run: emptyRun}
	const maxFlags = 50
	for i := 1; i < maxFlags; i += 2 {
		flagName := fmt.Sprintf("flag%d", i)
		rootCmd.Flags().String(flagName, "", fmt.Sprintf("test %s flag on root", flagName))
	}

	childCmd := &Command{
		Use: "child",
		Run: emptyRun,
	}
	for i := 2; i <= maxFlags; i += 2 {
		flagName := fmt.Sprintf("flag%d", i)
		childCmd.Flags().String(flagName, "", fmt.Sprintf("test %s flag on child", flagName))
	}

	rootCmd.AddCommand(childCmd)

	// Register completion in different threads to test concurrency.
	var wg sync.WaitGroup
	for i := 1; i <= maxFlags; i++ {
		index := i
		flagName := fmt.Sprintf("flag%d", i)
		wg.Add(1)
		go func() {
			defer wg.Done()
			cmd := rootCmd
			if index%2 == 0 {
				cmd = childCmd
			}
			_ = cmd.RegisterFlagCompletionFunc(flagName, func(cmd *Command, args []string, toComplete string) ([]string, ShellCompDirective) {
				return []string{fmt.Sprintf("flag%d", index)}, ShellCompDirectiveDefault
			})
		}()
	}

	wg.Wait()

	// Test that flag completion works for each flag
	for i := 1; i <= 6; i++ {
		var output string
		var err error
		flagName := fmt.Sprintf("flag%d", i)

		if i%2 == 1 {
			output, err = executeCommand(rootCmd, ShellCompRequestCmd, "--"+flagName, "")
		} else {
			output, err = executeCommand(rootCmd, ShellCompRequestCmd, "child", "--"+flagName, "")
		}

		if err != nil {
			t.Errorf("Unexpected error: %v", err)
		}

		expected := strings.Join([]string{
			flagName,
			":0",