Merge pull request #1796 from wxiaoguang/fix-nil-flag-v3

 Fix nil HelpFlag panic (v3)

command.go

@@ -527,6 +527,10 @@ func (cmd *Command) Run(ctx context.Context, osArgs []string) (deferErr error) {
 func (cmd *Command) checkHelp() bool {
 	tracef("checking if help is wanted (cmd=%[1]q)", cmd.Name)
 
+	if HelpFlag == nil {
+		return false
+	}
+
 	for _, name := range HelpFlag.Names() {
 		if cmd.Bool(name) {
 			return true

help_test.go

@@ -95,6 +95,24 @@ func Test_Help_Custom_Flags(t *testing.T) {
 	require.Len(t, out.String(), 0)
 }
 
+func Test_Help_Nil_Flags(t *testing.T) {
+	oldFlag := HelpFlag
+	defer func() {
+		HelpFlag = oldFlag
+	}()
+	HelpFlag = nil
+
+	cmd := &Command{
+		Action: func(_ context.Context, cmd *Command) error {
+			return nil
+		},
+	}
+	out := new(bytes.Buffer)
+	cmd.Writer = out
+	_ = cmd.Run(buildTestContext(t), []string{"test"})
+	require.Len(t, out.String(), 0)
+}
+
 func Test_Version_Custom_Flags(t *testing.T) {
 	oldFlag := VersionFlag
 	defer func() {

suggestions.go

@@ -31,7 +31,7 @@ func suggestFlag(flags []Flag, provided string, hideHelp bool) string {
 
 	for _, flag := range flags {
 		flagNames := flag.Names()
-		if !hideHelp {
+		if !hideHelp && HelpFlag != nil {
 			flagNames = append(flagNames, HelpFlag.Names()...)
 		}
 		for _, name := range flagNames {