From 1cbdb26dd1dd4f97c8ac1178d143fb76bc8c58ce Mon Sep 17 00:00:00 2001
From: Kenny Levinsen <kl@kl.wtf>
Date: Wed, 10 Jun 2020 14:13:19 +0200
Subject: [PATCH] service: Handle zero-value in stringPtrFlag.String

FlagSet.PrintDefaults uses reflection to construct a zero value, calls
.String on it, and compares the result with the current flag value to
detect zero-value flags. For stringPtrFlag, this would result in a
panic, as String() always dereferenced the first level of its **string.

Add another check so that both pointer levels are nil-checked.
---
 service.go | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/service.go b/service.go
index ef708e1..85dfe19 100644
--- a/service.go
+++ b/service.go
@@ -250,7 +250,7 @@ type stringPtrFlag struct {
 }
 
 func (f stringPtrFlag) String() string {
-	if *f.ptr == nil {
+	if f.ptr == nil || *f.ptr == nil {
 		return ""
 	}
 	return **f.ptr